This is a comparison of costs of different methods of heating.
I am assuming that we need about 9800kWh per year for heating (see ElectricityUsage for the derivation of this figure).
I am using the standard variable tariffs for electricity and gas on offer from Octopus on 4 Feb 2023:
| Tariff | Price per kWh | Standard charge per day |
|---|---|---|
| Electricity - Flexible Octopus October 2022 v1 | 34.23 | 42.77 |
| Gas - Flexible Octopus October 2022 v1 | 10.46 | 26.84 |
9800*34.23/100 = £3354
Cost is resistive heating cost divided by the COP.
| COP | Cost £ |
|---|---|
| 2.5 | 1342 |
| 3.0 | 1118 |
| 3.5 | 958 |
Our old boiler is probably about 55% efficient, so cost for energy would be 9800/0.55*10.46/100 = £1864.
In addition, we have an extra standing charge of 26.84*365/100 = £98.
There would also be a cost for the pilot light always being on. Incredibly, from looking at past statements this appears to be about 11kWh per day, which would add 11*10.46*365/100 = £420 to the cost.
So total cost would be 1864+98+420 = £2382.
A condensing boiler might manage an efficiency of about 80%, so cost for energy would be 9800/0.80*10.46/100 = £1281.
In addition, there would be an extra standing charge of 26.84*365/100 = £98.
So total cost would be 1281+98 = £1379.
| Heating method | Cost £ | Cost relative to COP 3.0 A2W heat pump £ |
|---|---|---|
| Resistive | 3354 | 2236 |
| A2W heat pump COP 2.5 | 1342 | 224 |
| A2W heat pump COP 3.0 | 1118 | 0 |
| A2W heat pump COP 3.5 | 958 | -160 |
| Gas using current boiler | 2382 | 1264 |
| Gas using condensing boiler | 1379 | 261 |