Estimates a house's heat loss and the heat pump that covers it, from a year of gas or oil bills, and says whether a quoted size looks plausible.
Most of the form is filled in already with figures that give a sensible answer. Adjust what you know and press the button.
Estimate the heat pump a UK house needs, and what it would cost to run against the fuel it burns now.
IMPORTANT: MIS 3005-D requires a heat pump to be sized from a room-by-room heat loss calculation to BS EN 12831, and nothing here replaces that. Say so whenever you report a result from this, and point the user at the room-by-room calculation. What the figure is for is checking whether a size somebody has been quoted is plausible, because oversizing is the commonest fault in heat pump installations and it is invisible to the person living with it.
There are two routes and the first is much the better one.
From metered fuel, which is preferred: give 'annualFuelUse' from a year of bills. The fuel becomes heat delivered, hot water comes off it using the MIS 3005-D formula, and what remains divided by the local heating degree days gives the building's heat loss coefficient in watts per kelvin. Degree days are computed from the Met Office monthly means published in MGD 007 section 5.
From the fabric, as a fallback when there are no bills: give 'floorAreaM2', an 'insulation' level and a 'propertyType'. The watts per kelvin per square metre behind this are a reasonable reading of British housing stock but they are NOT MCS figures, because MCS publishes no such shortcut. Say so when using this route.
Either way the peak load is the coefficient multiplied by the design temperature difference for the location, from Table 2 of MIS 3005-D. The heat pump must deliver at least that at the design outside temperature and the design flow temperature, which is not the same as its headline rating.
The result also compares what each of four flow temperatures would cost to run, which is the decision that governs the bill and the one a quotation most often leaves unstated. Supply 'quotedHeatPumpKw' to have a quoted size checked against the estimate.
The same calculation answers on
POST /api/v1/calculators/heat-pump-size
and as the MCP tool heat_pump_size.
How to call them.
It also runs from a plain link, with the JSON fields as query parameters: GET /api/v1/calculators/heat-pump-size?location=birmingham&fuel=mains_gas&annualFuelUse=12000&bedrooms=3&flowTemperature=45&fuelPricePerUnit=0.06&electricityPricePerKwh=0.25"edHeatPumpKw=8. This page takes its own form fields in the address in the same way, so an answer can be linked to.
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