Grid Impact of Heat Pumps

Grid impact in a heat pump environment is the effect that a heat pump has on the electricity network. It includes the heat pump’s electrical load, contribution to peak demand, effect on voltage and network capacity, and ability to shift consumption to a better time.

Grid impact assessment shows whether the grid connection can supply the heat pump reliably. It also shows whether the system could create high load peaks or offer useful flexibility.

Grid impact is managed through correct heat pump sizing, controlled auxiliary heating, inverter operation, thermal storage, smart metering and energy management. Photovoltaics, batteries and electric vehicle chargers must be coordinated with the heat pump.

This matters because a heat pump can be highly energy-efficient and still create a difficult electrical peak. Good grid integration protects comfort, prevents overload, reduces connection costs and helps electricity networks absorb more renewable energy.

Grid impact at a glance

• What it is: The effect of heat pump electricity consumption on the building connection and wider electricity grid.
• What it does: It changes electrical demand, peak power, network loading and the timing of electricity use.
• How to manage it: Size the system correctly, limit simultaneous loads, control backup heaters and use smart energy management.
• Why it matters: It supports reliable operation, affordable grid connections, lower peak costs and greater renewable energy use.

Definition of grid impact in a heat pump environment

Grid impact describes how a heat pump changes the demand placed on an electricity network. The grid sees the heat pump as an electrical load. It does not directly see the amount of heat delivered to the building.

The impact depends on both power and time. Power is measured in kilowatts, or kW. Energy consumption over a period is measured in kilowatt-hours, or kWh.

A heat pump can have low annual electricity consumption but still create a high peak load on a cold morning. The opposite is also possible. A heat pump may consume substantial annual electricity but operate with a smooth, predictable load profile.

The main grid-impact factors are:

• Maximum electrical input
• Duration of high-power operation
• Time of day
• Seasonal demand
• Simultaneous use by neighbouring buildings
• Use of electric backup heaters
• Interaction with photovoltaic systems
• Interaction with batteries and electric vehicles
• Modulation and start behaviour
• External control capability
• Available thermal storage
• Local grid capacity

Heat pumps extract energy from air, ground or water and use electrical energy to raise that heat to a useful temperature. Their deployment supports the transition away from fossil heating, but it also moves more building energy demand onto electricity networks.

Core purpose of grid impact assessment

The core purpose of grid impact assessment is to connect a heat pump without creating avoidable electrical problems. It links heating design with electrical design.

The assessment establishes how much grid capacity the building needs. It also identifies when the heat pump can operate flexibly without reducing comfort or hot-water availability.

A grid impact assessment supports five decisions:

1. Connection design: Determine the required main fuse, cable capacity, meter arrangement and contracted power.
2. Heat pump selection: Compare electrical input, modulation range, starting current and backup-heater control.
3. Control strategy: Decide how the heat pump responds to PV production, tariffs, grid signals and other loads.
4. Tariff selection: Compare fixed, time-of-use, dynamic and controllable-load tariffs.
5. Operational monitoring: Confirm that the installed system performs as designed.

The result should be a heat pump system that delivers the required heat while using the available electrical connection efficiently.

Why grid impact must be considered

Heat pumps create a new electrical heating load

A fossil boiler consumes fuel inside the building. A heat pump transfers much of this demand to the electricity system.

This change can reduce fossil-fuel use and overall primary energy demand. However, it also increases electricity demand at the building connection, local transformer and distribution feeder.

The International Energy Agency reported in its 2026 Heat Pump Monitor that heat pumps represented approximately 2% to 16% of annual peak electricity demand across major markets in 2024. The IEA described the peak impacts as manageable while also identifying heat pumps as a new source of demand flexibility.

The highest demand often occurs in cold weather

Heat demand rises as outdoor temperature falls. Air-source heat pump efficiency normally falls at the same time.

The compressor must therefore work harder. Defrost cycles may also occur. If an electric backup heater starts, the electrical load can rise sharply.

This makes the cold-weather operating point more important than the nominal data shown for mild conditions.

Many heat pumps can operate at the same time

A single residential heat pump is normally a manageable load. A neighbourhood of heat pumps can create a larger coincident peak.

Cold weather affects many buildings at once. Morning heating recovery and hot-water preparation can also occur at similar times.

This is called load coincidence. It is a central issue for local distribution system operators.

Other electrical loads increase the combined impact

The heat pump is rarely the only major electrical load. A modern building may also include:

• An electric vehicle charger
• A domestic battery
• Electric cooking
• Mechanical ventilation
• Comfort cooling
• A sauna
• Electric hot-water backup
• Commercial equipment
• Lift or building services

The grid connection must support the combined net load. Looking at the heat pump in isolation can therefore produce an incorrect result.

Poor integration creates real business problems

Unmanaged grid impact can result in:

• A delayed grid-connection approval
• A more expensive connection upgrade
• Higher capacity or demand charges
• Main fuse operation
• Unnecessary backup-heater use
• Reduced heat-pump efficiency
• Low PV self-consumption
• High simultaneous demand from heating and EV charging
• Comfort complaints during control periods
• Premature equipment wear
• Difficult commissioning
• Disputes between the installer, electrician, operator and building owner

A system-level design addresses these risks before installation.

Key features of heat pump grid impact

Grid impact has several connected features. Each feature describes a different part of the relationship between the heat pump, building and electricity network.

The principal features are:

1. Net power at the grid connection
2. Peak electrical demand
3. Connection capacity
4. Load coincidence
5. Seasonal and daily load profile
6. Modulation and start behaviour
7. Auxiliary-heater demand
8. Thermal flexibility
9. Power quality and phase balance
10. Measurement and verification

Detailed explanation of grid-impact features

Net power at the grid connection

Definition: Net power is the electricity imported from or exported to the public grid at the building’s connection point.

Purpose: It shows the load that the distribution grid must actually supply. Device-level heat pump consumption alone does not show this value.

Benefits: Using net power as the control variable allows the building to coordinate the heat pump with PV, batteries, EV charging and other loads.

Example: A heat pump consumes 4 kW while a PV system produces 3 kW. The resulting grid import is approximately 1 kW, assuming no other building loads.

A basic representation is:

Grid import = building consumption − local generation − battery discharge

The calculation changes continuously. The control system should therefore use live meter data where possible.

For connection planning, designers should not assume that PV power will always be available. Winter heating peaks can occur before sunrise, after sunset or during low solar production.

Peak electrical demand

Definition: Peak electrical demand is the highest power drawn by the heat pump or complete building during a defined measurement interval.

Purpose: It determines whether cables, protective devices, meters, transformers and contracted power are adequate.

Benefits: Reducing the peak can avoid connection upgrades and lower capacity-based network costs.

Example: A compressor draws 4 kW. An electric backup heater adds 6 kW. The heating system can therefore create a 10 kW peak if both operate together.

Peak demand must include:

• Compressor input at the design outdoor temperature
• Source and circulation pumps
• Fans
• Crankcase or tray heaters
• Defrost operation
• Domestic hot-water production
• Electric backup or immersion heaters
• Simultaneous cooling or secondary loads
• Cascade units in larger systems

The nominal thermal capacity of the heat pump is not the same as its electrical peak.

Grid-connection capacity

Definition: Grid-connection capacity is the maximum electrical power that the building is permitted and technically able to import.

Purpose: It provides the boundary within which the heat pump and all other electrical equipment must operate.

Benefits: Correct capacity planning prevents nuisance trips, connection delays and excessive fixed charges.

Example: A building has an available import limit of 18 kW. The heat pump, EV charger and household loads could together require 27 kW. A load-management system keeps the combined import below 18 kW by reducing EV charging and staging the backup heater.

Connection capacity may be defined by:

• Main fuse rating
• Contracted power
• Agreed connection power
• Cable and switchgear capacity
• DSO connection agreement
• Transformer or feeder constraints
• A dynamic power limit
• A controllable-load agreement

The correct term and calculation method vary by country and network operator.

Coincidence and diversity

Definition: Coincidence describes how often several loads reach high power at the same time. Diversity describes the degree to which their operating times differ.

Purpose: These factors help estimate the real combined peak of multiple devices or buildings.

Benefits: A realistic coincidence assessment avoids both undersizing and unnecessary overinvestment.

Example: Ten 5 kW heat pumps do not necessarily create a constant 50 kW load. However, a cold-weather morning can produce a high coincident demand if all units recover temperature and prepare hot water at the same time.

Coincidence should be assessed at several levels:

• Inside one dwelling
• Across a multi-apartment building
• Across a development
• On a distribution feeder
• At the local transformer
• Across an aggregated heat pump fleet

Simple fixed diversity factors may be inadequate for highly electrified developments. Time-series modelling gives a more reliable result.

Seasonal and time-of-day load profile

Definition: The load profile shows how electrical demand changes over time.

Purpose: It reveals when the heat pump places the greatest load on the grid and when it can shift consumption.

Benefits: Load-profile analysis supports tariff selection, storage sizing and control programming.

Example: A residential air-source heat pump may show a winter morning peak. A reversible heat pump in Spain or northern Italy may also contribute to a summer afternoon cooling peak.

Important profile periods include:

• The coldest winter day
• Morning heating recovery
• Evening occupancy
• Domestic hot-water cycles
• Defrost events
• Low-temperature nights
• High-PV midday periods
• Summer cooling periods
• Dynamic-price minima
• DSO congestion windows

Annual energy data cannot reveal these conditions. Interval data is required.

Modulation, ramp rate and starting behaviour

Definition: Modulation is the ability of a heat pump to vary compressor output. Ramp rate describes how quickly electrical demand changes.

Purpose: Controlled modulation allows the heat pump to follow the actual heat requirement instead of repeatedly switching between full power and off.

Benefits: Smooth operation can reduce electrical peaks, start cycles, mechanical wear and temperature variation.

Example: An inverter heat pump increases its electrical input gradually from 1.5 kW to 4 kW. A fixed-speed unit may start directly at its full operating level.

Relevant characteristics include:

• Minimum compressor input
• Maximum compressor input
• Modulation ratio
• Starting current
• Soft-start or inverter control
• Minimum operating time
• Minimum off-time
• Ramp-rate control
• Cascade sequencing
• Recovery after a control event

A low minimum output is valuable during mild weather. However, the system must still cover the design load efficiently in cold conditions.

Auxiliary and backup heating

Definition: Auxiliary heating is an additional heat source that supports the compressor. It is commonly an electric resistance heater.

Purpose: It covers peak heat demand, supports hot-water production or provides emergency heating.

Benefits: Correct staging protects comfort without creating unnecessary grid peaks.

Example: A 3 kW compressor and 9 kW electric heater could draw 12 kW together. A controller may limit the heater to one 3 kW stage while an EV is charging.

Backup-heater control should define:

• Outdoor-temperature release point
• Maximum permitted electrical stage
• Delay before activation
• Interaction with compressor output
• Interaction with grid-import limits
• Interaction with domestic hot water
• Emergency operating mode
• Behaviour during defrost
• Manual override
• Alarm and reporting logic

Uncontrolled resistance heating is one of the most common causes of an unexpectedly high heat pump grid impact.

Thermal storage and load shifting

Definition: Thermal storage holds heat for later use. It may use a water tank, domestic hot-water cylinder, floor heating system or the thermal mass of the building.

Purpose: It separates the time of heat production from the time of heat use.

Benefits: The heat pump can reduce operation during a grid peak and increase operation when electricity, PV production or network capacity is more favourable.

Example: The heat pump raises the floor or buffer temperature slightly before an expected evening peak. It then reduces compressor demand while the building releases the stored heat.

For water storage:

Thermal energy = water mass × specific heat capacity × temperature change

A practical approximation is:

1,000 litres of water stores about 1.16 kWh of heat per 1°C temperature change

A 500-litre buffer with a usable 5°C temperature range therefore stores approximately 2.9 kWh of heat.

Storage must be designed carefully. Excessive storage temperature can reduce heat pump efficiency. Oversized tanks can also increase standing losses, space requirements and installation cost.

Demand response and external control

Definition: Demand response is a deliberate change in electrical demand in response to a price, grid or market signal.

Purpose: It moves or reduces load when the electricity system is under stress. It can also increase consumption when renewable electricity is abundant.

Benefits: Demand response can reduce peaks, create financial value and support renewable energy integration.

Example: An energy management system preheats the building and then reduces heat pump input for 45 minutes during a local grid constraint.

EU electricity rules define demand response as a change from a normal consumption pattern in response to market signals, time-variable prices, incentive payments or an accepted demand-reduction offer. EU rules also support aggregation and dedicated measurement of flexible, controllable loads.

A complete demand-response function should manage:

• Signal reception
• Maximum power
• Minimum heat delivery
• Comfort limits
• Hot-water priority
• Frost protection
• Compressor protection
• Event duration
• Recovery strategy
• Rebound prevention
• User information
• Fail-safe operation

A control event should not cause every heat pump to restart at full power at the same moment. Staggered recovery prevents a new rebound peak.

Power quality and phase balance

Definition: Power quality describes voltage, frequency, harmonics, flicker and other electrical characteristics at the connection. Phase balance describes how evenly a three-phase network is loaded.

Purpose: These requirements protect the heat pump, other building equipment and the public network.

Benefits: Correct electrical design improves reliability and reduces the risk of local voltage problems.

Example: A high-power single-phase load can create phase imbalance. A suitable three-phase connection distributes the load more evenly.

The electrical designer should verify:

• Permitted single-phase power
• Three-phase requirements
• Starting current
• Harmonic compliance
• Power factor
• Voltage-drop limits
• Cable sizing
• Protective-device coordination
• Residual-current protection
• Earthing
• Surge protection
• DSO technical connection rules

In Germany, VDE-AR-N 4100 provides the national technical framework for low-voltage customer connections. Its current scope includes the integration of controllable consumption equipment. Local technical connection conditions still apply.

Measurement and verification

Definition: Measurement and verification compare expected grid impact with actual operating data.

Purpose: They show whether the heat pump follows the planned power limits and control strategy.

Benefits: Monitoring identifies excessive backup heating, poor scheduling, short cycling and unplanned simultaneous loads.

Example: Meter data shows a recurring 16 kW morning peak. Analysis finds that the heat pump, immersion heater and EV charger start at 06:00. Revised schedules reduce the peak to 10 kW.

Useful measurements include:

• Heat pump electricity consumption
• Complete building import and export
• Compressor input
• Backup-heater input
• Thermal output
• Flow and return temperatures
• Outdoor temperature
• Domestic hot-water temperature
• PV generation
• Battery power
• EV charging power
• Room temperature
• Control-event status

The most useful grid measurement is normally taken at the building’s point of connection.

How to assess heat pump grid impact

Step 1: Define the system boundary

Decide whether the study covers the heat pump only or the complete building. A connection assessment should normally cover the complete building.

For a development or multi-apartment property, include the shared connection, transformer or feeder where relevant.

Step 2: Collect heating and electrical data

Collect:

• Design heat loss
• Design outdoor temperature
• Required flow temperature
• Domestic hot-water demand
• Heat pump performance data
• Compressor electrical input
• Backup-heater capacity
• Existing connection capacity
• Main fuse rating
• Current load profile
• PV size and orientation
• Battery power and capacity
• EV charger rating
• Tariff structure
• DSO requirements
• Planned control interfaces

Use performance data for the actual design condition. Mild-weather catalogue values are not sufficient for peak assessment.

Step 3: Estimate compressor electrical demand

A simplified relationship is:

Electrical input = required thermal output ÷ COP

For example:

• Required heat output: 10 kW
• COP at the design condition: 2.5
• Approximate compressor input: 4 kW

This is an initial estimate. Final design should use certified manufacturer performance tables, including fans and pumps where applicable.

Step 4: Add auxiliary electrical loads

Add the possible electrical input of:

• Backup heater
• Immersion heater
• Source pump
• Heating circulation pumps
• Fan
• Defrost support
• Trace heating
• Controls
• Other heating-system auxiliaries

Assess both normal and emergency operation.

Step 5: Build a time-based load profile

Model at least:

• A normal winter day
• A design-cold winter day
• A domestic hot-water peak
• A day with EV charging
• A day with low PV production
• A summer cooling day where relevant
• A DSO or tariff-control event
• Recovery after a control event

Use the interval required by the tariff or network operator. Short intervals reveal peaks that monthly energy values hide.

Step 6: Calculate coincident building demand

Combine the heat pump with all other major loads. Apply realistic operating logic rather than adding every nameplate rating without context.

However, do not assume diversity where no control exists. An EV charger and heat pump can operate simultaneously unless a control system prevents it.

Step 7: Compare demand with the connection limit

Check:

• Main fuse capacity
• Contracted power
• Permitted phase loading
• Cable capacity
• DSO connection conditions
• Available controllable-load tariff
• Required meter architecture
• Smart-meter availability

A deficit can be resolved through a connection upgrade or through verified load management.

Step 8: Test control scenarios

Compare at least four cases:

1. Uncontrolled operation
2. Heat pump scheduling
3. Whole-building power limiting
4. Coordinated heat pump, PV, battery and EV operation

Measure the change in peak import, energy cost, comfort and backup-heater use.

Step 9: Select the control hierarchy

A practical priority order is:

1. Protect people and equipment.
2. Maintain frost protection.
3. Maintain essential hot water.
4. Respect the grid-import limit.
5. Use the heat pump efficiently.
6. Use available PV energy.
7. Charge the battery or EV.
8. Respond to price signals.
9. Restore comfort gradually after an event.

The exact order depends on the building and user requirements.

Step 10: Commission and monitor

Commissioning must test actual operating states. It should not stop after confirming that the compressor starts.

Test:

• Maximum compressor operation
• Backup-heater staging
• Hot-water priority
• DSO input
• SG Ready or digital interface
• PV-surplus mode
• Import limiting
• EV coordination
• Sensor failure
• Communication failure
• Power restoration
• Recovery after curtailment

Monitor the first heating season and correct the control parameters where necessary.

Practical calculation example

A house has the following equipment:

• Heat pump compressor: 4 kW maximum input
• Backup heater: 6 kW
• EV charger: 11 kW
• Household load: 4 kW
• Grid-connection limit: 16 kW

The unmanaged maximum is:

4 + 6 + 11 + 4 = 25 kW

The building exceeds the 16 kW connection limit by 9 kW.

A coordinated energy manager can apply the following sequence:

1. Limit the backup heater to 3 kW.
2. Reduce EV charging from 11 kW to 5 kW.
3. Keep the compressor at 4 kW.
4. Reserve 4 kW for household loads.

The controlled demand becomes:

4 + 3 + 5 + 4 = 16 kW

The building stays within its grid limit without stopping the heat pump.

Types of grid-impact operating models

Unmanaged heat pump

Definition: The heat pump operates only according to internal heating and hot-water demand.

Purpose: It provides basic thermal comfort.

Benefit: Installation and control are simple.

Practical application: A small heat pump is connected to a building with ample electrical capacity and no PV, EV or variable tariff.

The limitation is that the unit does not consider total grid import or external network conditions.

Inverter-modulating heat pump

Definition: The compressor adjusts its output to the current heat demand.

Purpose: It reduces on-off operation and follows the heating load more closely.

Benefit: It can create a smoother electrical profile and improve seasonal efficiency.

Practical application: A well-sized inverter unit operates continuously at low input during moderate winter conditions.

Scheduled or time-of-use operation

Definition: The heat pump changes operation according to fixed tariff or time windows.

Purpose: It shifts selected loads away from expensive or congested periods.

Benefit: It is simple to implement and predictable.

Practical application: Domestic hot-water preparation is scheduled for a lower-tariff period.

The limitation is that fixed schedules cannot react to changing PV output, weather or real-time grid conditions.

PV-optimized operation

Definition: The heat pump increases useful operation when on-site PV surplus is available.

Purpose: It converts surplus solar electricity into stored heat.

Benefit: It can increase PV self-consumption and reduce midday export.

Practical application: The system raises the domestic hot-water target when sustained PV export exceeds a defined threshold.

PV optimization is not automatically the same as grid optimization. The controller must also prevent excessive building import when PV output falls suddenly.

Grid-controllable operation

Definition: The heat pump responds to an external DSO or utility control signal.

Purpose: It reduces or limits electrical demand during a local network constraint.

Benefit: It can support connection approval and access to reduced network charges.

Practical application: The DSO communicates a temporary import limit. The heat pump controller reduces input while maintaining frost protection and basic heat supply.

HEMS-coordinated operation

Definition: A home energy management system coordinates the heat pump with other building assets.

Purpose: It manages the complete net load at the connection point.

Benefit: It can prioritize comfort while preventing simultaneous peaks from the heat pump, EV and battery.

Practical application: The HEMS slows EV charging when the heat pump starts a domestic hot-water cycle.

BEMS-controlled central heat pump

Definition: A building energy management system controls a larger or central heat pump installation.

Purpose: It coordinates plant operation, storage, tenant demand and building services.

Benefit: It supports demand-charge reduction, plant sequencing and detailed monitoring.

Practical application: A hotel preheats a large domestic hot-water store before the morning occupancy peak.

Aggregated flexibility model

Definition: An aggregator controls or coordinates many heat pumps as one flexible portfolio.

Purpose: It allows small loads to participate collectively in electricity or flexibility markets.

Benefit: The aggregated portfolio can provide a material demand change even when each heat pump contributes only a few kilowatts.

Practical application: Thousands of residential units reduce input slightly for a short balancing event and then recover in staggered groups.

Heat pump grid-impact use cases

Single-family home with PV and EV charging

The problem is simultaneous demand. The heat pump, vehicle and household can exceed the main connection capacity.

The solution is whole-building power management. The system reads net grid import and adjusts flexible loads.

A practical control order is:

1. Maintain the heat pump compressor.
2. Limit or delay the backup heater.
3. Reduce EV charging.
4. Charge the battery only when spare capacity remains.
5. Increase thermal charging during genuine PV surplus.

This approach can avoid an unnecessary connection upgrade.

Renovation with a limited electrical connection

An older property may have a small main fuse or weak local connection. Increasing the connection may be expensive or slow.

The project should select a heat pump with low design-condition input, a suitable modulation range and staged auxiliary heating. Building-envelope improvements can reduce both thermal and electrical peak demand.

The final design should demonstrate that the complete building remains within the agreed limit.

Multi-apartment building

A central heat pump serves many occupants. Domestic hot-water peaks and circulation losses can create substantial demand.

The control system should coordinate compressor stages, buffer storage, hot-water charging and tenant-side loads. It should also record thermal and electrical performance.

The business benefits include lower demand charges, better operating transparency and fewer comfort complaints.

New residential development

A development can add dozens or hundreds of similar heat pumps to one distribution area. Their combined peak can determine transformer and feeder upgrades.

The developer should provide the DSO with realistic time-series demand data. Coordinated controls and sensible domestic hot-water schedules can reduce artificial coincidence.

The assessment should include EV adoption because charging demand may become larger than the heating load.

Hotel, care facility or commercial building

These buildings often have high domestic hot-water demand and capacity-based electricity costs. They may also require strict temperature and hygiene control.

The heat pump should be integrated with a BEMS. Storage can shift production without compromising hygiene requirements.

The system should optimize both kilowatt-hours and peak kilowatts.

Industrial or district heating heat pump

A large heat pump can become a significant controllable electricity load. It may use industrial waste heat, wastewater, surface water or another low-temperature source.

Thermal storage allows the plant to separate electricity use from heat delivery. The operator may then respond to energy prices, local grid limits or flexibility-market signals.

Large systems require detailed connection studies, protection design and contractual coordination with the network operator.

Energy community or local microgrid

A heat pump can absorb local renewable production and reduce export. It can also compete with batteries and EVs for the same surplus electricity.

An energy manager should optimize the complete community rather than each device independently. Shared limits and transparent priorities prevent one asset from creating a new peak for other participants.

Benefits of managing heat pump grid impact

Benefits for building owners

• More reliable heating
• Lower risk of main-fuse trips
• Better use of available connection capacity
• Lower exposure to peak charges
• Improved use of PV electricity
• Greater compatibility with dynamic tariffs
• Reduced unnecessary backup heating
• Better operational data
• Easier addition of EV charging or battery storage

Benefits for businesses and property operators

• Lower demand costs
• Better investment planning
• Reduced connection-upgrade risk
• Measurable energy performance
• Improved asset management
• More predictable operating expenditure
• Potential access to flexibility revenues
• Easier environmental and energy reporting

Benefits for installers and planners

• Fewer commissioning problems
• Clearer responsibility between trades
• Better DSO communication
• Lower risk of undersized electrical equipment
• Lower risk of oversized heating equipment
• More defensible design decisions
• Greater customer confidence

Benefits for grid operators

• Lower coincident peak demand
• Improved transformer utilization
• Reduced local congestion
• More predictable demand
• Better renewable energy integration
• Delayed or avoided network reinforcement
• Access to distributed flexibility
• Controlled recovery after network events

Selection criteria for a grid-compatible heat pump system

Electrical input at the design condition

Select the heat pump using its electrical input at the local design outdoor temperature. Do not rely only on nominal COP or thermal output at mild conditions.

Ask for:

• Compressor input at the design point
• Maximum operating current
• Starting current
• Input during domestic hot-water production
• Input during defrost
• Maximum auxiliary-heater input

Modulation range

A wide, useful modulation range helps the heat pump match changing demand. It can reduce start cycles and smooth the load profile.

Check whether the minimum output is appropriate for the building’s spring and autumn heat demand.

Backup-heater staging

The controller should expose clear settings for each heater stage. It should permit power limiting, delayed release and integration with a site import limit.

An all-or-nothing backup heater can create avoidable peaks.

External control interfaces

Determine which interfaces are available:

• Dry contact
• SG Ready inputs
• Modbus TCP
• Modbus RTU
• BACnet
• EEBUS
• Manufacturer API
• Digital tariff input
• DSO control interface
• PV inverter connection

The interface must support the required control function. A label alone does not guarantee complete interoperability.

Whole-building import limiting

The energy manager should measure net power at the point of connection. It should then allocate available capacity among the heat pump, EV, battery and other controllable assets.

Device-only control cannot guarantee a building-wide limit.

Thermal storage capability

Assess the building mass, floor heating, buffer vessel and domestic hot-water cylinder. Determine how much flexibility each component can provide without excessive temperature or heat loss.

More storage is not always better. The best solution uses the lowest practical storage temperature.

Tariff and market compatibility

Check whether the system supports:

• Fixed tariffs
• Time-of-use tariffs
• Dynamic energy prices
• Time-variable network charges
• Controllable-load tariffs
• Aggregator signals

A tariff optimization function should include heat pump efficiency. The lowest electricity price does not always produce the lowest heating cost if the heat pump must operate at a less efficient outdoor temperature.

Meter and data requirements

Confirm:

• Smart-meter availability
• Meter interval
• Separate or shared heat pump metering
• Import and export measurement
• Data access rights
• Local API availability
• DSO control equipment
• Cybersecurity requirements

A control strategy cannot operate reliably without the necessary measurements.

Fail-safe behaviour

The heat pump must continue to protect the building if communication fails.

Check the fallback state for:

• Lost internet connection
• Lost smart-meter data
• Lost PV data
• Invalid price data
• Failed external contact
• DSO gateway failure
• Sensor failure
• Power interruption

Safety, frost protection and equipment protection take priority over optimization.

Monitoring and service

Select a system that records both heat and electricity data. Clear event logs should show when external limits, backup heaters or tariff functions are active.

Remote diagnostics can reduce service time, but local operation must remain possible.

Important comparisons

Grid impact vs electricity consumption

Grid impact concerns power, timing and local network effects.

Electricity consumption concerns the total energy used over a period.

A system can reduce annual kWh without reducing the highest kW peak.

Grid impact vs environmental impact

Grid impact concerns network capacity, voltage, peaks and flexibility.

Environmental impact includes energy source, greenhouse gas emissions, refrigerant, materials, noise and lifecycle effects.

The two topics are related but not interchangeable.

Grid-friendly vs energy-efficient

Energy-efficient operation minimizes electricity used for a given heat output.

Grid-friendly operation uses electricity at times and power levels that reduce network stress.

The optimal strategy should address both. Raising storage temperatures may improve timing but reduce COP.

Smart meter vs energy management system

A smart meter measures and communicates electricity data.

An energy management system uses data to make control decisions.

A smart meter does not normally coordinate the heat pump, EV and battery by itself.

SG Ready vs complete smart-grid integration

SG Ready generally provides basic external operating states.

Complete smart-grid integration can include live power limits, forecasts, prices, meter data, optimization and verification.

SG Ready can be one interface within a broader system.

PV optimization vs grid optimization

PV optimization increases local use of solar electricity.

Grid optimization manages import and export according to local network needs.

The two objectives often support each other, but not always. A local grid may be constrained even during a low wholesale-price period.

Thermal storage vs electrical battery

Thermal storage stores useful heat. It is often suitable when the future requirement is heating or hot water.

A battery stores electricity. It can support several electrical loads and reduce net import, but it adds cost and conversion losses.

A coordinated system decides which storage asset should respond.

Load shifting vs peak shaving

Load shifting moves electricity use to another time.

Peak shaving directly reduces the highest import level.

A shifted load can create another peak if the recovery period is not controlled.

Integration with other systems

Integration with photovoltaic systems

Definition: PV integration links heat pump operation with on-site solar production.

Purpose: It uses available solar electricity for space heating, cooling or hot water.

Benefits: It can increase self-consumption and reduce export.

Example: The heat pump raises the hot-water target only after the meter detects sustained PV export.

A good PV strategy should:

• Use net-meter data
• Apply a minimum surplus threshold
• Include a delay to avoid rapid switching
• Respect maximum storage temperatures
• Consider heat pump COP
• Return smoothly to normal operation
• Maintain a grid-import limit
• Coordinate with the battery and EV

Integration with battery storage

Definition: Battery integration coordinates electrical charging and discharging with the heat pump.

Purpose: It manages the complete power balance at the building connection.

Benefits: A battery can reduce short peaks and supply the heat pump during a temporary grid limit.

Example: The battery discharges 3 kW while the heat pump prepares hot water, keeping total grid import below the contracted level.

The controller should prevent the battery from charging from the grid at the same time as a heat pump peak unless the connection has sufficient capacity.

Integration with EV charging

Definition: EV integration coordinates vehicle charging with heating demand.

Purpose: It prevents two large flexible loads from creating an avoidable combined peak.

Benefits: The building may support both systems without increasing connection capacity.

Example: EV charging reduces from 11 kW to 4 kW when the heat pump begins a high-temperature hot-water cycle.

EV charging is usually more deferrable than space heating. It is therefore often the first load reduced by a home energy manager.

Integration with building thermal mass

Definition: The floors, walls and internal structure act as a low-temperature heat store.

Purpose: The building can receive slightly more heat before a peak period and slightly less during it.

Benefits: Thermal mass can provide flexibility without a large additional buffer tank.

Example: Room setpoints rise by 0.5°C before an evening network peak. The heat pump then reduces operation while indoor temperature remains within the accepted comfort range.

Room sensing is important. Control should use defined comfort limits rather than uncontrolled overheating.

Integration with HEMS or BEMS

Definition: HEMS means home energy management system. BEMS means building energy management system.

Purpose: These systems coordinate measurements, forecasts, power limits and equipment priorities.

Benefits: They create one control strategy for the complete building.

Example: A BEMS combines weather forecasts, occupancy, electricity prices, buffer temperature and the building import limit to schedule a central heat pump.

The system should use open, documented interfaces where possible.

Integration with smart meters and tariffs

Definition: A smart meter provides interval electricity data. A tariff assigns a price to energy or network use.

Purpose: Meter and tariff data allow the heat pump to respond to time-dependent costs.

Benefits: The operator can shift flexible consumption and verify the financial result.

Example: The heat pump prepares hot water during a low network-tariff window while maintaining the same daily hot-water service.

Dynamic price control should not operate without a power limit. Many devices responding to the same low price can create a synchronized load increase.

Integration with DSOs and aggregators

Definition: The DSO manages the local distribution grid. An aggregator pools many small flexible loads.

Purpose: The DSO uses flexibility to address local constraints. The aggregator makes small heat pump loads large enough to participate collectively.

Benefits: Building owners may receive network-charge reductions or flexibility payments where the national framework permits them.

Example: An aggregator receives a network request and distributes a small power reduction across a heat pump fleet.

Control contracts should define availability, event duration, minimum comfort, measurement, compensation and override rules.

Integration with weather and occupancy data

Definition: Predictive control uses expected weather and building use to plan heat production.

Purpose: It prepares the correct amount of stored heat before a tariff or grid event.

Benefits: The system can shift load without excessive temperature increases.

Example: The controller expects a warmer afternoon and avoids charging the buffer fully during the morning.

Forecasts should support the control strategy. They should not replace live temperature and power measurements.

Regulatory and market context

European Union

EU electricity law supports active customers, demand response, aggregation, smart metering and flexible electrical loads. The 2024 electricity market reform also enables dedicated measurement arrangements for controllable appliances so that customers can participate in incentive-based demand response.

For a heat pump project, this means the technical design should anticipate:

• External control
• Interval metering
• Dynamic or time-dependent tariffs
• Aggregator participation
• Separate measurement where useful
• Data exchange with energy management systems

Germany

Germany applies specific rules to new controllable consumption equipment under §14a EnWG. Since 1 January 2024, new heat pumps with a grid-connection power above 4.2 kW fall within the framework, including associated electric backup or emergency heaters.

During a concrete local network overload, the DSO may temporarily reduce the grid-supplied power of a directly controlled device to a defined minimum. For many installations, that minimum is 4.2 kW. In return, the operator receives a network-charge reduction. Germany also requires DSOs to offer the time-variable network-charge Module 3 in combination with Module 1 from April 2025.

The practical design should therefore check:

• Whether the heat pump exceeds 4.2 kW connection power
• Whether direct control or EMS control will be used
• Meter arrangement
• §14a tariff module
• Smart Meter Gateway requirements
• DSO technical connection conditions
• Control of the backup heater
• Combined control with PV, battery and EV charging

Austria

Austria is moving toward stronger time-dependent and flexibility-based network tariffs. For 2026, E-Control introduced a reduced daytime network energy component for eligible network-level 7 customers during high-PV periods. E-Control also introduced a flexible-withdrawal arrangement initially focused on higher network levels, while broader tariff reform continues.

Austrian projects should verify:

• Current Systemnutzungsentgelte
• Smart-meter data permissions
• Local network operator requirements
• Existing interruptible or dual-tariff arrangements
• Available daytime or flexible-withdrawal products
• Meter and switching architecture
• Transition rules for existing heat pump installations

Switzerland

Swiss network operators have significant responsibility for setting network-use tariffs. From the 2026 tariff year, operators can introduce dynamic network tariffs based on next-day grid loading or time-variable capacity tariffs, subject to the applicable legal conditions. The actual tariff therefore depends on the local network operator.

Swiss projects should check:

• Local Netznutzungstarif
• Smart-meter availability
• High/low tariff periods
• Dynamic tariff options
• Compensation for controllable loads
• Local DSO switching rules
• Cantonal requirements
• Contractual power or fuse limits

Italy, including German-speaking South Tyrol

Italian customers operate with an agreed potenza impegnata, or contracted power. A heat pump, EV charger or electric renovation may require an increase in this capacity. The request process depends on the connection level and is normally handled through the electricity supplier for low-voltage customers.

Projects should verify:

• Contracted power
• Single-phase or three-phase connection
• Meter capacity
• Local distributor requirements
• Electrical connection standard
• Available tariff structure
• PV and storage configuration
• Building-level load management

German-language project documentation does not change the applicable Italian connection rules.

Spain

For low-voltage consumers with contracted power up to 15 kW, Spain’s 2.0TD network structure uses two contracted-power periods and three energy periods. This makes both the selected power level and the timing of heat pump operation relevant.

Spanish projects should consider:

• Heating and cooling demand
• Two-period contracted power
• Three-period energy charges
• Summer cooling peaks
• Midday PV production
• Domestic hot-water scheduling
• EV charging
• Maximum building import

Poland

Poland offers single-zone and multi-zone household tariffs, including G11, G12 and G13 structures. Large electricity suppliers must also offer dynamic-price contracts to eligible customers, with a remotely read smart meter required for these products.

Cold-climate projects should pay particular attention to:

• Design-temperature COP
• Backup-heater capacity
• Smart-meter availability
• Dynamic or multi-zone tariff conditions
• Morning and evening winter peaks
• Main connection capacity
• Defrost and recovery behaviour

Finland

Dynamic-price electricity contracts are already widely used in Finland. Energy Authority data show that approximately one-third of Finnish households had a dynamic-price contract in 2024, creating a strong use case for automated, price-responsive heat pump control.

Finnish projects should still combine price optimization with:

• A building import limit
• Cold-weather performance analysis
• Controlled electric backup
• Comfort constraints
• DSO tariff assessment
• Staggered recovery
• Reliable operation during extreme temperatures

Grid impact is the relationship between heat pump operation and electricity-network conditions. It is determined by electrical power, operating time, simultaneous loads, control behaviour and available flexibility.

A good heat pump design does not focus only on annual electricity use. It also considers the cold-weather peak, backup heater, building connection, PV system, battery, EV charger and local grid rules.

The practical objective is clear: deliver reliable heating with the lowest reasonable electrical peak and the greatest useful flexibility. Correct sizing, whole-building power management, thermal storage and open control interfaces turn the heat pump from an unmanaged load into a coordinated part of the energy system.

Frequently asked questions

Do heat pumps overload the electricity grid?

A single correctly designed heat pump does not normally overload the grid. Problems can occur when the building connection is undersized, electric backup heating is uncontrolled or many large loads operate simultaneously.

At neighbourhood level, many heat pumps can create a high coincident winter peak. Grid planning and flexible control reduce this risk.

Is heat pump grid impact always negative?

No. A heat pump increases electrical demand, but it can also provide useful flexibility.

The system can absorb surplus renewable electricity, shift heat production and reduce demand during selected peak periods. The outcome depends on the heat pump, building, storage and control strategy.

Does a PV system remove the grid impact of a heat pump?

No. PV can reduce daytime grid import, but it does not guarantee electricity during winter peaks or at night.

The connection must normally support operation when PV output is low. PV should be treated as an operational benefit rather than an unconditional replacement for grid capacity.

Is an efficient heat pump automatically grid-friendly?

No. Efficiency and grid friendliness are different performance dimensions.

An efficient heat pump uses less electricity for each unit of heat. A grid-friendly system also controls when that electricity is used and how high the building’s peak demand becomes.

Is SG Ready enough for grid integration?

SG Ready can provide useful basic external control. It may support blocking, normal operation or increased operation states.

A complete grid-integration strategy may also require live meter data, variable power limits, PV coordination, EV management, forecasts and event verification.

Can a grid operator switch off a heat pump?

The answer depends on national rules and the connection agreement. Modern frameworks increasingly favour controlled power reduction rather than complete disconnection.

In Germany, new qualifying controllable heat pumps under §14a EnWG must retain a defined minimum grid-supplied power during a control event. Other countries and DSOs apply different arrangements.

Are dynamic electricity tariffs always grid-friendly?

No. Dynamic energy prices reflect electricity-market conditions. They do not always represent a constraint on the local distribution feeder.

A robust system combines price optimization with a maximum building import and any available DSO signal.

Can a larger buffer tank solve grid-impact problems?

A buffer tank can provide load-shifting capacity, but it is not a complete solution. Its value depends on usable temperature range, building demand and control quality.

A large tank can increase heat loss and installation cost. Raising its temperature too far can reduce heat pump efficiency.

Which heat pump has the lowest grid impact?

There is no single model that has the lowest impact in every building. The result depends on heat loss, source temperature, flow temperature, electrical input, backup heater, control interfaces and other building loads.

The best system is normally a correctly sized modulating heat pump with controlled auxiliary heating and whole-building energy management.

What is the most important grid-impact measurement?

The most important measurement is usually the maximum net electricity import at the building’s point of connection.

Device-level data are still required to explain why the peak occurred.