The baseline:<\/strong> What uncontrolled or previous peak is used for comparison?<\/li>\n<\/ol>\nA claim such as \u201cthe system reduces peaks\u201d has little technical value unless these three elements are defined.<\/p>\n
Peak demand at different system boundaries<\/h3>\nHeat pump equipment peak<\/h4>\n
This is the maximum electrical input of the heat pump unit and its directly associated components. It may include the compressor, fan, source pump, circulation pump and internal electric heater.<\/p>\n
This boundary is useful for heat pump product control. It does not show the complete load on the building connection.<\/p>\n
Heating plant peak<\/h4>\n
This is the combined electrical demand of the heat pump plant. It can include multiple heat pumps, external circulation pumps, electric heaters, domestic hot-water equipment and hydraulic auxiliaries.<\/p>\n
This boundary is important for plant-room electrical design and cascade control.<\/p>\n
Building or site peak<\/h4>\n
This is the maximum import measured at the building\u2019s point of connection. It includes the heat pump, lighting, appliances, ventilation, electric vehicle charging and other building loads. Photovoltaic generation and battery discharge can reduce the measured grid import.<\/p>\n
This is usually the most relevant boundary for contracted power, demand charges, main-fuse capacity and grid connection studies.<\/p>\n
Grid-level coincident peak<\/h4>\n
This is the combined demand of many buildings at the same time. A control action can reduce the peak of one building without reducing the wider network peak. Large-scale peak demand reduction therefore requires coordination, diversity and appropriate grid signals.<\/p>\n
Peak demand is measured in kW, not kWh<\/h3>\n
A kilowatt measures power. It describes how fast electricity is being used at a given time.<\/p>\n
A kilowatt-hour measures energy. It describes the total quantity of electricity consumed over time.<\/p>\n
A heat pump can use the same number of kilowatt-hours per day while producing a lower peak in kilowatts. The control system achieves this result by spreading consumption across a longer period.<\/p>\n
Basic peak demand calculation<\/h3>\n
Peak demand for a defined interval can be represented as:<\/p>\n
Peak demand = maximum interval energy \u00f7 interval duration<\/strong><\/p>\nFor example, a building that imports 3.6 kWh during a 15-minute interval has an average demand of:<\/p>\n
3.6 kWh \u00f7 0.25 hours = 14.4 kW<\/strong><\/p>\nA five-second compressor or motor surge is not the same as a 15-minute demand peak. Starting current remains important for cables, protection and voltage quality, but it may have little effect on a tariff based on average 15-minute demand.<\/p>\n
Basic site-demand relationship<\/h3>\n
A simplified building power balance is:<\/p>\n
Grid import = heat pump demand + auxiliary heating + other building demand + EV charging + battery charging \u2212 PV production \u2212 battery discharge<\/strong><\/p>\nPeak reduction can then be calculated as:<\/p>\n
Peak reduction in kW = baseline peak \u2212 controlled peak<\/strong><\/p>\nPeak reduction in % = peak reduction \u00f7 baseline peak \u00d7 100<\/strong><\/p>\nThe baseline should represent comparable weather, occupancy, hot-water use and operating conditions.<\/p>\n
<\/span>Core purpose of peak demand reduction<\/span><\/h2>\nThe core purpose is to deliver the required heating, cooling and domestic hot water with a lower maximum electrical draw. The system changes when and how thermal energy is produced. It does not simply remove the thermal service.<\/p>\n
A well-designed strategy follows a clear priority order:<\/p>\n
\n- Protect people, equipment and the building.<\/li>\n
- Maintain minimum comfort and domestic hot-water requirements.<\/li>\n
- Keep the heat pump within its permitted operating range.<\/li>\n
- Respect the building or grid power limit.<\/li>\n
- Optimise electricity cost, renewable energy use and system efficiency.<\/li>\n<\/ol>\n
The control system should therefore distinguish between essential and flexible demand. Space heating may be temporarily reduced within a narrow comfort range. A domestic hot-water hygiene cycle, frost-protection function or safety-related process may have higher priority.<\/p>\n
What peak demand reduction is intended to achieve<\/h3>\n