Why the Tariff Matters as Much as the Heat Pump
You can install a brilliant heat pump and still pay too much if you leave it on a standard variable tariff. The right electricity tariff is the single easiest lever to cut running costs — often the difference between a heat pump costing about the same as gas and it costing clearly less.
The key is a time-of-use tariff designed for heat pumps, which rewards you for heating during cheaper off-peak windows.
How Heat-Pump Tariffs Work
The best-known is Cosy Octopus, which uses a triple-dip structure:
- Three cheap off-peak windows a day — typically 04:00–07:00, 13:00–16:00 and 22:00–00:00 — at around half the standard rate.
- A peak window (16:00–19:00) priced higher.
- Standard rate the rest of the time.
By scheduling heating and hot water into the cheap windows and coasting through the peak, your blended electricity rate can drop to around 17p/kWh — which is what makes a heat pump cheaper to run than gas.
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What to Look For in a Tariff
When comparing heat-pump tariffs, check:
- Off-peak rate and window length — cheaper and longer is better.
- Peak rate and timing — how easily can you avoid it?
- Eligibility — most require a registered heat pump and a SMETS2 smart meter.
- Export rate — if you have solar, how well does it pay for export?
- Standing charges and any exit fees.
The best tariff for you depends on your daily routine and whether you have solar and a battery.
Combine Tariff, Solar and Battery for the Lowest Bills
The lowest running costs come from stacking three things:
1. A smart heat-pump tariff for cheap off-peak heating. 2. Solar panels for free daytime generation — great for the midday window and hot water. 3. A battery to store cheap off-peak or surplus solar energy and use it during the expensive evening peak.
Designed together, these turn a heat pump into the cheapest way to heat a UK home. When we design a system, we factor your likely tariff and any solar/battery in from the start so the whole thing works as one.
Frequently asked questions
Time-of-use heat-pump tariffs such as Cosy Octopus are usually the best value because their cheap off-peak windows blend your rate down to around 17p/kWh. The ideal choice depends on your routine and whether you have solar and a battery.
Yes — these tariffs generally require a SMETS2 smart meter (or compatible SMETS1) sending half-hourly readings, plus a registered heat pump that you can schedule to heat during the cheap windows.
Absolutely, and it is the ideal combination. Solar covers daytime generation, the tariff covers cheap off-peak heating, and a battery bridges the expensive peak — together giving the lowest possible running costs.
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