Heating Cost Calculator
Calculator
Heating Cost Calculator
How much you spend in a year to heat your home, based on floor area, climate zone, building age and heating system
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How the calculation works
The calculator estimates how much you spend in a year on heating alone, excluding hot water and cooking. It first works out the heat the home needs, then converts it into the fuel you have to buy:
Heat (kWh/year) = floor area (m²) × degree-days (DD) × age coefficient (kWh per m² and per DD) × home type factor
Cost (€/year) = heat ÷ system efficiency ÷ calorific value × price
Degree-days (DD) are the unit that measures how cold a municipality is: for each day of the heating season, you count the degrees the average outdoor temperature falls short of 20 °C, then add them up. The calculation runs in your browser and no data is sent anywhere.
Degree-days used for each zone
If you only choose the climate zone, the calculator uses the median of the municipalities in that zone. If you know your municipality’s degree-days, enter them in the field provided: they replace the zone value.
| Zone | Legal band (DD) | Value used (DD) | Example municipalities (DD) |
|---|---|---|---|
| A | up to 600 DD | 573 DD | Lampedusa 568 DD |
| B | 601-900 DD | 789 DD | Palermo 751 DD |
| C | 901-1,400 DD | 1,187 DD | Naples 1,034 DD |
| D | 1,401-2,100 DD | 1,768 DD | Rome 1,415 DD, Florence 1,821 DD |
| E | 2,101-3,000 DD | 2,512 DD | Milan 2,404 DD, Turin 2,617 DD |
| F | over 3,000 DD | 3,388 DD | Cuneo 3,012 DD, Belluno 3,043 DD |
Home coefficients
The coefficient says how much heat is needed per square metre and per degree-day. It starts from the median values of the 2024 Italian energy performance certificates (APE) and is calibrated on the gas consumption measured by ARERA, because certificates describe a home heated throughout and always at 20 °C, which rarely happens in real life.
| Year built | Coefficient (kWh per m² and per DD) |
|---|---|
| Before 1945 | 0.038 kWh/m² DD |
| 1945-1976 | 0.032 kWh/m² DD |
| 1977-1991 | 0.030 kWh/m² DD |
| 1992-2005 | 0.028 kWh/m² DD |
| 2006-2015 | 0.021 kWh/m² DD |
| Since 2016 | 0.011 kWh/m² DD |
A home with more outside walls loses more heat. Compared with an apartment, the calculator multiplies the heat by 1.35 for a terraced house and by 1.47 for a detached house, the ratios from the European TABULA project for Italian buildings of 1991-2005.
Efficiencies, calorific values and prices
| System | Efficiency (%) | Calorific value | All-inclusive price |
|---|---|---|---|
| Condensing natural gas boiler | 86% | 9.849 kWh/Smc | 1.768 €/Smc |
| Conventional natural gas boiler | 75% | 9.849 kWh/Smc | 1.768 €/Smc |
| Condensing LPG boiler | 86% | 6.82 kWh/litre | 2.483 €/litre |
| Heating oil boiler | 77% | 9.94 kWh/litre | 2.07 €/litre |
| Pellet stove | 80% | 4.8 kWh/kg | 0.507 €/kg |
| Pellet boiler | 77% | 4.8 kWh/kg | 0.507 €/kg |
| Wood stove | 70% | 397 kWh/quintal | 21.7 €/quintal |
| Air-to-water heat pump | SCOP 2.9-3.1 | 1 kWh/kWh | 0.4343 €/kWh |
| Electric radiators | 100% | 1 kWh/kWh | 0.4343 €/kWh |
Efficiencies are typical values over a whole season, lower than the rated ones. For the heat pump, SCOP says how many kWh of heat each kWh of electricity delivers: the calculator uses 3.1 up to 1,400 DD, 3.0 up to 2,100 DD and 2.9 above that.
Prices have different dates: ARERA natural gas for October 2026, ARERA electricity for October-December 2026, MASE heating oil of 2 November 2026, LPG from the Modena Chamber of Commerce price list of 15 October 2026, AIEL pellets for September 2026, AIEL firewood for April 2026. They are a starting point: if you have a bill, divide the total by the consumption and enter your own price.
Worked example
A 90 m² apartment in Milan (2,404 DD), built in 1985, with a condensing natural gas boiler:
- Heat: 90 m² × 2,404 DD × 0.030 kWh/m² DD = 6,491 kWh/year
- Energy to buy: 6,491 kWh ÷ 0.86 = 7,548 kWh/year
- Natural gas: 7,548 kWh ÷ 9.849 kWh/Smc = 766 Smc/year
- Cost: 766 Smc × 1.768 €/Smc = about €1,350 per year
How much it costs to heat 100 m²
Estimated annual cost for a 100 m² apartment built in 1977-1991, at the prices in the table above:
| Zone | Condensing natural gas (€/year) | Heat pump (€/year) | Pellet stove (€/year) |
|---|---|---|---|
| A (573 DD) | €360 | €240 | €230 |
| B (789 DD) | €490 | €330 | €310 |
| C (1,187 DD) | €740 | €500 | €470 |
| D (1,768 DD) | €1,110 | €770 | €700 |
| E (2,512 DD) | €1,570 | €1,130 | €990 |
| F (3,388 DD) | €2,120 | €1,520 | €1,340 |
Why your cost may be different
The estimate describes an average home of that age. Temperature, hours of use, closed rooms, floor and exposure can move the result a lot. Today’s price is applied to the whole year, while gas and electricity change all the time. If you have last year’s bills, they remain the best figure. For the full bill with fixed charges and real consumption, use the energy-bill calculator, and to read the items on the bill see the guide to electricity and gas bills.
Frequently asked questions
How much does it cost to heat a 100 m² home?
It depends on the zone and the system. A 100 m² apartment built in 1977-1991 with a condensing natural gas boiler uses about 625 Smc a year in zone D and about 890 Smc in zone E: multiply by the natural gas price, or see the table above. A detached house of the same age uses 47% more.
How do I find my municipality’s degree-days?
They are in annex A of Italian Presidential Decree 412/1993, and many municipal websites and heating system logbooks also list them. If you cannot find them, the climate zone is enough.
Does the calculation include hot water and cooking?
No, only heating. According to Eurostat, heating accounts for about 75% of the gas used in Italian homes: the rest goes to hot water and cooking, and on your bill you will find it on top of this estimate.
I added external insulation and new windows: which year should I choose?
Choose 2006-2015. After a full renovation an old home has a heat demand similar to that of buildings from those years.
Sources
Degree-days and zones: Presidential Decree 412/1993 and ENEA table. Coefficients: annual report on building energy certification by ENEA and CTI (2024 APE data), TABULA, Politecnico di Torino, ARERA gas consumption 2024-2025. Prices: ARERA gas, ARERA electricity, MASE, Modena Chamber of Commerce, AIEL.
