Heating Cost Calculator
Work out your gas bill per year and per month, how much of it goes to heating, and what turning the thermostat down saves.
Heating cost per year
£1,068.00
Per month
£89.00
Of which heating
£691.20
Saving with the thermostat lower
£38.02
Gas saved per year
475 kWh
Please note: The result is an estimate and has been rounded. Actual costs and values may differ, and no rights can be derived from this calculation.
Gas use varies from year to year with the weather; the saving per degree is a rule of thumb.
How this number is calculated
The blocks use your input. Change a value above and they update with it.
Step 1 · Gas cost without fixed charges
Step 2 · Heating cost per year
Step 3 · Gas for heating
Step 4 · Saving on heating
Step 5 · Gas saved
Step 6 · Saving with the thermostat lower
How the calculation works
Work out what you spend on gas per year and per month, how much of it goes to heating, and what it saves to turn the thermostat down.
Your heating cost is your gas use times the gas price, plus the fixed charges for the gas supply. Not all gas goes to heating: some is for hot water and cooking. When you turn the thermostat down, you save on the gas for heating. The calculator uses a fixed percentage per degree, a common rule of thumb.
Formula
Heating cost = gas use × gas price + fixed charges. Gas for heating = gas use × share for heating. Gas saved = gas for heating × degrees lower × saving per degree (at most 100%). Saving = gas saved × gas price.
Assumptions
- The gas price is a fixed rate per unit, including taxes.
- The saving per degree is a rule of thumb; in a well-insulated home it is often smaller, in a draughty home larger.
- The gas use is for a year with ordinary weather. A cold winter costs more.
- Internally the calculator uses Dutch gas at 9.77 kWh per m³. kWh and therms convert exactly; UK and US gas holds more energy per m³.
Example calculations
The button fills in the calculator above, so you can carry on from there.
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Home using 1,200 m³ of gas
Heating cost per year
£1,980.00
Gas use per year 1,200 m³ · Gas price £1.35 per m³ · Fixed gas charges per year £360.00 · Share for heating (%) 72 · Thermostat lower (degrees) 1 · Saving per degree (%) 10 · m³
-
Two degrees lower
Heating cost per year
£1,980.00
Gas use per year 1,200 m³ · Gas price £1.35 per m³ · Fixed gas charges per year £360.00 · Share for heating (%) 72 · Thermostat lower (degrees) 2 · Saving per degree (%) 10 · m³
-
Small flat
Heating cost per year
£810.00
Gas use per year 600 m³ · Gas price £1.35 per m³ · Fixed gas charges per year £0.00 · Share for heating (%) 70 · Thermostat lower (degrees) 1 · Saving per degree (%) 10 · m³
Frequently asked questions
What does turning the thermostat down save?
With 12,000 kWh of gas a year, 72% of it for heating, and 5.5% saving per degree, turning down by 1 degree saves 475 kWh, or 38.02 a year at 0.08 per kWh.
Why is my heating cost different every year?
How much you heat depends a lot on the weather. A cold winter uses more gas than a mild one. Compare several years, or use an average.
Is the saving per degree Celsius or Fahrenheit?
Per degree on your own thermostat. The default of 5.5% is per degree Celsius; per degree Fahrenheit it is about 3%. Enter the degrees and the percentage in the same unit.
What are the fixed charges?
The standing charge or customer charge for your gas connection. You pay it however little gas you use; it only goes away if you stop using gas altogether.
What if I get a heat pump?
Then you use less gas and more electricity. The heat pump calculator shows what that changes per year and how long a heat pump takes to pay back.
Sources and checks
Sources
- Gas meter readings and bill calculation | GOV.UK
- Energy price cap unit rates and standing charges | Ofgem
- NIST Guide to the SI, Appendix B.9: Factors for units listed by kind of quantity or field of science
How we check it
This calculator has 10 fixed checks: 7 calculations with a result that is fixed in advance, and 3 cases of invalid input that must be rejected. They all run automatically every time we publish; if one fails, the calculator does not go live.
See the calculations
- Gas use per year 1,200 m³ · Gas price £1.35 per m³ · Fixed gas charges per year £360.00 · Share for heating (%) 72 · Thermostat lower (degrees) 1 · Saving per degree (%) 10 · m³ → Heating cost per year £1,980.00
- Gas use per year 1,200 m³ · Gas price £1.35 per m³ · Fixed gas charges per year £360.00 · Share for heating (%) 72 · Thermostat lower (degrees) 2 · Saving per degree (%) 10 · m³ → Heating cost per year £1,980.00
- Gas use per year 600 m³ · Gas price £1.35 per m³ · Fixed gas charges per year £0.00 · Share for heating (%) 70 · Thermostat lower (degrees) 1 · Saving per degree (%) 10 · m³ → Heating cost per year £810.00
- Gas use per year 1,500 m³ · Gas price £1.40 per m³ · Fixed gas charges per year £300.00 · Share for heating (%) 80 · Thermostat lower (degrees) 0 · Saving per degree (%) 6 · m³ → Heating cost per year £2,400.00
- Gas use per year 1,000 m³ · Gas price £1.40 per m³ · Fixed gas charges per year £0.00 · Share for heating (%) 100 · Thermostat lower (degrees) 5 · Saving per degree (%) 30 · m³ → Heating cost per year £1,400.00
- Gas use per year 12,000 kWh · Gas price £0.08 per kWh · Fixed gas charges per year £108.00 · Share for heating (%) 72 · Thermostat lower (degrees) 1 · Saving per degree (%) 5.5 · kWh → Heating cost per year £1,068.00
- Gas use per year 410 therms · Gas price £2.05 per therm · Fixed gas charges per year £150.00 · Share for heating (%) 75 · Thermostat lower (degrees) 2 · Saving per degree (%) 6 · therms → Heating cost per year £990.50
Changes
- : First version. Defaults follow the Ofgem price cap (gas 0.08, standing charge 108); the saving per degree is now 5.5% per °C, derived from the US Department of Energy. Sources added.
Last reviewed: · How we build and check our calculators
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