Running costs
Heating cost calculator
Work out how much heat your home or room needs, then what it costs to make with each fuel at the prices you pay. Nothing is looked up online: you enter your own tariffs, in any currency.
Heat and running cost
Heat-loss coefficient 277 W/°C, 2,033 °C·days. Costs a year.
13,515 kWh of heat a year
461 therms · 46.1 million BTU estimate
- Cheapest hereGas boiler or furnace1,051 a year
- Dearest hereElectric heaters3,379 a year
Running cost a year
At these prices a heat pump costs the same to run as the gas boiler at a seasonal COP of 3.21. Above that it is cheaper; below it, gas is.
| Heating, price and efficiency | Fuel used | Per kWh of heat | Cost |
|---|---|---|---|
| Electric heaters0.25 per kWh · 100% | 13,515 kWh | 0.250 | 3,379 |
| Heat pump0.25 per kWh · COP 3 | 4,505 kWh | 0.083 | 1,126 |
| Gas boiler or furnace (cheapest)0.07 per kWh · 90% | 15,017 kWh | 0.078 | 1,051 |
| Heating oil boiler0.80 per litre · 85% | 1,483 litres | 0.088 | 1,186 |
| Propane (LPG) boiler0.75 per litre · 90% | 2,121 litres | 0.118 | 1,591 |
| Wood stove (logs)0.30 per kg · 70% | 4,709 kg | 0.105 | 1,413 |
Prices are the ones you entered, in your own currency. Standing charges, maintenance and the cost of the appliance are not included.
How to use the heating cost calculator
- Choose how to find the heat needed: from a heat-loss coefficient and your area's degree-days, from a heater's output and the hours you run it, or from a yearly figure you already have.
- Enter the price you pay for each fuel and the unit it is sold in. Untick anything you cannot get.
- Set each appliance's efficiency, or a heat pump's seasonal COP, from its label or manual.
How it works
Degree-days add up how far, and for how long, the outside temperature falls below a base temperature. Multiplying them by the heat-loss coefficient (watts per degree) and 24 hours gives the heat needed in a year. Each appliance then has to buy that heat ÷ its efficiency in fuel: an electric heater turns every kWh into a kWh of heat, a boiler at 90% needs 1.11 kWh of gas for each, and a heat pump with a COP of 3 needs only a third of a kWh of electricity.
Fuel bought by the litre, gallon, therm, kilogram or cord is converted to kWh with the energy contents listed below.
Worked example
The 1970s semi from the heat loss calculator loses 277 W per °C. With 2,033 degree-days (the figure MCS gives for London postcodes), it needs 277 × 2,033 × 24 ÷ 1,000 ≈ 13,500 kWh of heat a year. At an example gas price of 0.07 a kWh and 90% efficiency that is about 1,050; at 0.25 a kWh for electricity, a heat pump with a COP of 3 costs about 1,130 and electric heaters about 3,380.
Energy contents and degree-days
| Fuel and unit | kWh | Basis |
|---|---|---|
| Natural gas, per therm | 29.31 | 100,000 BTU by definition |
| Natural gas, per m³ / per 100 ft³ | 10.72 / 30.36 | EIA: 1,036 BTU per cubic foot |
| Heating oil, per US gallon / per litre | 40.59 / 10.72 | EIA: 138,500 BTU per gallon |
| Propane, per US gallon / per litre | 26.80 / 7.08 | EIA: 91,452 BTU per gallon |
| Logs, per kg, air-dry (20% moisture) | 4.1 | Forest Research net calorific value |
| Firewood, per cord | 5,861 | EIA: 20 million BTU per cord |
Real fuel varies: gas suppliers measure its calorific value, oil grades differ a little, and wood depends heavily on species and dryness. If your bill shows gas in kWh, choose "per kWh" and the conversion does not matter.
Degree-days for the UK by postcode area run from about 1,800 to 2,700 a year to a 15.5 °C base (MCS, from Met Office records). In the United States, NOAA and many utilities publish heating degree days to a 65 °F base; switch the units above to enter them in °F·days and the coefficient in BTU/h·°F. Degree-day websites can also work out figures for a weather station near you.
Comparing energy tariffs or asking several installers for heat-pump quotes? Comparison sites and quote forms want an email address first. A free CleanTempMail inbox takes the replies, with no sign-up, and clears itself after 3 days, so the sales follow-ups stay out of your own email.
Sources
- US Energy Information Administration, British thermal units (Btu): sample conversion factors for heating oil, propane, natural gas, electricity and cord wood.
- Forest Research, Typical calorific values of fuels: log wood, stacked and air dry at 20% moisture, 4.1 kWh/kg net.
- MCS, Heat Load Calculator: design conditions: heating degree-days by UK postcode area, base 15.5 °C, from Met Office records.
Questions
How much does it cost to run a 2 kW heater?
A 2 kW electric heater uses 2 kWh for every hour it runs at full power, so multiply 2 by your electricity price per kWh. At 0.25 a kWh that is 0.50 an hour. Its thermostat switches it off once the room is warm, so a whole day usually costs less than 24 full hours.
Is a heat pump cheaper to run than a gas boiler?
It depends on the ratio between your electricity and gas prices and on the heat pump's seasonal COP. The calculator shows the break-even COP: if electricity costs 3.2 times as much per kWh as gas heat from a 90% boiler, the heat pump needs a COP above 3.2 to be cheaper.
What is a degree-day?
For each day, it is how many degrees the average outdoor temperature falls below a base temperature, added up over the year. A day averaging 5.5 °C counts 10 degree-days to a 15.5 °C base. The base sits below room temperature because people, appliances and sunshine provide the rest of the heat.
What efficiency should I enter for my boiler or stove?
Use the seasonal efficiency on the appliance's label, manual or energy certificate where you can. The starting values here (90% gas, 85% oil, 90% propane, 70% wood stove, COP 3 for a heat pump) are only placeholders; older appliances and open fires are often much less efficient.
Why doesn't the calculator use current energy prices?
Prices differ by country, supplier and tariff and change often, so any built-in figure would be wrong for most people. Your bill shows exactly what you pay per unit, and the calculator works in any currency.