The Real Running Costs of a Heat Pump: One Year On
After 12 months with an air source heat pump, we share the actual running costs, electricity usage, and comparison to our old gas boiler.
A year ago, we replaced our 18-year-old gas combi boiler with a Vaillant Arotherm Plus 7kW air source heat pump. The house is a 1960s 3-bed semi in Nottinghamshire with cavity wall insulation and decent loft insulation. Here's exactly what happened to our energy bills.
The monthly breakdown
| Month | Heat pump kWh | Cost | Gas equivalent (est.) |
|---|---|---|---|
| March | 520 | £67 | £78 |
| April | 310 | £40 | £45 |
| May | 140 | £18 | £22 |
| June | 60 | £8 | £12 |
| July | 45 | £6 | £10 |
| August | 50 | £6 | £10 |
| September | 120 | £15 | £18 |
| October | 380 | £49 | £62 |
| November | 550 | £71 | £88 |
| December | 680 | £88 | £105 |
| January | 720 | £93 | £112 |
| February | 580 | £75 | £90 |
Annual total: 4,155 kWh electricity, £536. Estimated gas equivalent: £652. Saving of £116 on running costs.
The tariff makes a huge difference
Those figures are on a standard variable tariff at 24p/kWh. I've since switched to a heat pump tariff offering 15p/kWh for off-peak hours. On that tariff, the same usage would cost roughly £380/year - saving £272 compared to gas.
If you haven't checked what energy tariffs are available for heat pump owners, it's the single biggest thing you can do to improve the economics.
Comfort is genuinely better
The gas boiler cycled on and off constantly, creating temperature swings. The heat pump runs at low output for longer periods, maintaining a steady 20-21C throughout the house. No cold spots. The hot water is consistent too.
The cold snap test
January saw a week of -5C to -8C overnight. The heat pump coped without issue, though the COP dropped from 3.5 to about 2.3 during the coldest nights. The house stayed warm. We didn't need supplementary heating.
Would we do it again?
Without hesitation. The £7,500 BUS grant brought our out-of-pocket cost to £4,800. At £270+ annual savings on a heat pump tariff, the payback is under 18 years, and the system should last 20-25 years.
For accurate projections for your home, start with our running cost calculator and then get quotes from local installers. Every home is different, and a proper heat loss survey will give you much more accurate figures than generic estimates.
If you're also trying to decide between heat pump types, we compared air source vs ground source in detail.
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