Heat source selection guide
A heat pump, an electric boiler or a gas condensing boiler – which one pays off for heating your home, and at what output? Homeowners and tradespeople alike ask this before they place a first order. The guide on this page gives you a first estimate based on figures. There is no need to register or to wait for a quotation.
You answer five questions: how large the heated area is, how high the ceilings are and how many people live in the house, how well the house is insulated, which heat source you are considering, what will heat the rooms (radiators, underfloor heating or both) and how you want to heat water. Finally, you can adjust the gas and electricity prices per kWh. With every change the result is recalculated and displayed:
- an estimate of the heat loss of the house (kW) and of the heat source output worth aiming for,
- the annual consumption of heat for heating and hot water (kWh),
- the annual and monthly costs if you heated with gas, electricity or a heat pump,
- approximate parameters for the circulation pump, expansion vessel, hot water cylinder, radiators or underfloor heating (pipe length, number of circuits) and links to matching searches in our shop.
How the guide calculates
- Heat loss in kW = area × ceiling height × specific heat loss ÷ 1,000. The specific heat loss is 15 W/m³ for a new build or low-energy house, 25 W/m³ for an insulated house with plastic windows, 40 W/m³ for an uninsulated house and 55 W/m³ for an old house with its original windows.
- Annual space-heating demand = heat loss × 24 h × 3,400 degree days ÷ 32 K × 0.7. The value 3,400 corresponds to the climate of central Slovakia, 32 K is the difference between 20 °C indoors and −12 °C outdoors, and the coefficient 0.7 allows for internal and solar gains.
- Hot water: we assume 50 litres per person per day, heated by 30 K, all year round, with a 15 % allowance for losses.
- Costs: the energy consumption is divided by an efficiency of 0.95 for a gas boiler, 0.99 for an electric boiler and by the seasonal performance figure SCOP for a heat pump (3.0 with radiators, 4.0 with underfloor heating and with a combination of the two); the result is multiplied by the energy price you enter.
- Heat source output: the heat loss increased by 10 %. If the boiler heats the water on demand (instantaneously), the guide assumes an output of at least 24 kW.
The result is only an estimate and works with typical values for the level of insulation. Precise sizing is a job for a design engineer, who calculates the heat loss according to EN 12831.
The cost comparison does not cover solid fuel boilers. If you are considering a wood or pellet boiler, or would like to discuss the result with an adviser, write to info@atriashop.eu or call +421 917 133 662 (Mon–Fri 7:30–15:30 CET). Companies and tradespeople can register in the shop and, once approved, buy at their own prices.