How is the required heating capacity calculated?

Two homes with the same floor area can have different heating needs. The assessment considers the building fabric, windows, airtightness, ventilation, desired indoor temperature and local outdoor design conditions. Final heat pump selection also needs to match the system water temperature and the manufacturer's capacity data. ^S11

A simple way to illustrate the calculation is: floor area × selected heat demand per unit area. For example, if an educational scenario assumes 50 W/m² for a 120 m² home, the result is 6 000 W, or 6 kW. This explains the calculation, but does not provethat a 6 kW unit suits a real 120 m² home. The 50 W/m² figure is not a universal standard here.

Do not confuse power and energy. Kilowatts describe instantaneous power; kilowatt-hours describe energy over time. Annual energy demand and heating capacity on the coldest day are not the same quantity.

Domestic hot water is assessed separately according to usage and equipment operating strategy; it should not arbitrarily become the same extra capacity allowance for everyone. ^S10

Before ordering: provide a design or as much building information as possible. Use the website's indicative calculator for an initial discussion, not as a final equipment order.