OneTaskBy Tim King · Updated
Heating Cost Calculator
Boiler, Heat Pump and Air Con Running Cost Per Hour and Month
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How the Heating and Cooling Cost Calculator works
This heating cost calculator works out what a boiler, heat pump, electric heater, wood stove or air-conditioner costs to run. Enter the heat output in kW, the hours it runs each day and the price you pay per kWh of gas, oil or electricity, and it returns the energy bought and the cost per hour, per day and over a month or season.
A heater's output is the heat it puts into the room; what you pay for is the fuel or electricity it draws to make that heat. The gap between the two is the efficiency. A modern condensing gas boiler turns about 90% of its gas into heat, a plain electric heater turns 100% of its electricity into heat, and a heat pump moves three to four units of heat for every unit of electricity, so its efficiency (the coefficient of performance, COP) is 300–400%.
How the heating cost calculator works
The formula is energy bought = output (kW) × hours ÷ efficiency, and cost = energy bought × price per kWh. For example, a 5 kW gas boiler running 6 hours a day at 90% efficiency buys 5 × 6 ÷ 0.9 = 33.3 kWh of gas a day; at 0.08 a kWh that is 2.67 a day. A second example: the same 5 kW of heat from a heat pump with a COP of 3.5 needs 8.6 kWh of electricity, which at 0.25 a kWh is 2.14 a day.
Air-conditioning works the same way: enter the cooling output in kW and pick the heat pump option, since a reverse-cycle unit's cooling efficiency (EER) is close to its heating COP. If you know the exact seasonal figure from the label, type it into the efficiency box.
To see how many kWh a whole season costs, set the days to the length of your heating season. Energy prices change often, so use the unit rate on your latest bill rather than an average. Gas and oil are sometimes billed in cubic metres, therms or litres; convert those to kWh first (one litre of heating oil is about 10.3 kWh, one therm is 29.3 kWh).
Cost of 5 kW of heat for 6 hours a day over 30 days, by system and energy price per kWh
| Price per kWh | Gas boiler | Oil boiler | Electric heater | Heat pump (COP 3.5) |
|---|---|---|---|---|
| 0.04 | 40.00 | 42.35 | 36.00 | 10.29 |
| 0.06 | 60.00 | 63.53 | 54.00 | 15.43 |
| 0.08 | 80.00 | 84.71 | 72.00 | 20.57 |
| 0.10 | 100.00 | 105.88 | 90.00 | 25.71 |
| 0.12 | 120.00 | 127.06 | 108.00 | 30.86 |
| 0.14 | 140.00 | 148.24 | 126.00 | 36.00 |
| 0.16 | 160.00 | 169.41 | 144.00 | 41.14 |
| 0.18 | 180.00 | 190.59 | 162.00 | 46.29 |
| 0.20 | 200.00 | 211.76 | 180.00 | 51.43 |
| 0.22 | 220.00 | 232.94 | 198.00 | 56.57 |
| 0.24 | 240.00 | 254.12 | 216.00 | 61.71 |
| 0.26 | 260.00 | 275.29 | 234.00 | 66.86 |
| 0.28 | 280.00 | 296.47 | 252.00 | 72.00 |
| 0.30 | 300.00 | 317.65 | 270.00 | 77.14 |
| 0.32 | 320.00 | 338.82 | 288.00 | 82.29 |
| 0.34 | 340.00 | 360.00 | 306.00 | 87.43 |
| 0.36 | 360.00 | 381.18 | 324.00 | 92.57 |
| 0.38 | 380.00 | 402.35 | 342.00 | 97.71 |
| 0.40 | 400.00 | 423.53 | 360.00 | 102.86 |
| 0.42 | 420.00 | 444.71 | 378.00 | 108.00 |
| 0.44 | 440.00 | 465.88 | 396.00 | 113.14 |
| 0.46 | 460.00 | 487.06 | 414.00 | 118.29 |
FAQ
Is a heat pump cheaper to run than a gas boiler?
It depends on the ratio of electricity to gas prices. A heat pump with a COP of 3.5 beats a 90% boiler whenever electricity costs less than about 3.9 times the gas price per kWh. Enter both systems with your own prices to see which wins where you live.
How much does it cost to run a 2 kW electric heater?
A 2 kW heater draws 2 kWh every hour it runs flat out. Multiply 2 by your electricity price per kWh for the hourly cost; at 0.25 a kWh that is 0.50 an hour, or 3.00 for six hours. A thermostat that cycles the heater off will lower the real figure.
Why does my heater cost less than the calculator says?
Most heaters and boilers modulate or cycle once the room reaches temperature, so they rarely run at full output for every hour they are switched on. Use the average output, often half to two-thirds of the rated figure, for a closer estimate of what your bill will show.
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