Heating energy calculator
Annual heating energy is roughly the heated floor area multiplied by a specific demand per m² that depends on insulation. The calculator gives the yearly total and a monthly average, so you can compare insulation levels or heating options.
Your measurements
Result
- Estimated annual heating energy
- 8,000 kWh
- Monthly average
- 667 kWh
Real consumption depends on the local climate, the temperature you keep and the efficiency of the heating system.
How the calculation works
- Annual use (kWh) = floor area × specific demand: about 150 kWh/m² per year uninsulated, 80 for a modern insulated house and 30 for a very low-energy house.
- Monthly average = annual use ÷ 12.
Worked example
A 100 m² modern insulated house uses about 100 × 80 = 8,000 kWh a year for heating, on average 667 kWh a month. The same house uninsulated would use about 15,000 kWh.
What the calculator assumes
- The specific values are averages for a continental climate (they come from our Romanian calculator); colder or milder climates differ.
- Heating is concentrated in about six months, so the monthly average is only a guide.
- Price per kWh of heat: for gas, the price per kWh on the bill divided by the boiler efficiency; for a heat pump, the electricity price divided by the COP (usually 3–4).
When to adjust the result
- Domestic hot water isn't included: add roughly 600–800 kWh a year per person.
- The set temperature matters: each extra degree raises consumption by about 6%.
- An energy performance certificate, where one exists, gives a better figure for your house.
Using the heating-demand figure
The calculated heat demand is the basis for sizing radiators, a boiler or a heat pump. Losses come from walls, roof, floor and windows, plus ventilation; in older homes, draughts and the roof are often the biggest items.
Use it to compare improvements: insulating the roof or replacing single-glazed windows often cuts demand more than any change of heat source. For a final design, a professional room-by-room calculation to your local standard is worth it.
Frequently asked questions
How much energy does it take to heat a house?
Roughly 30–150 kWh per m² per year depending on insulation; a 100 m² well-insulated house might need about 8,000 kWh.
How much does lowering the thermostat save?
About 6% of heating energy for each degree lower, as a rule of thumb.
What is a typical heat demand per m²?
Very well-insulated new homes may need well under 50 W/m² at design temperature; older uninsulated houses often need 100 W/m² or more.
Which improvement saves the most?
Usually roof insulation and draught-proofing first, then walls and windows — the calculator shows where your losses are.