Which tariff is actually right for a heat pump?

The short answer

Only two mainstream tariffs are actually open to a home with a heat pump and no electric car: Octopus Cosy and British Gas Heat Power. Both give several hours of discounted electricity a day built around a heating pattern rather than a car charging overnight. Two other tariffs that rank well in search for “heat pump tariff” and “octopus heat pump tariff”, Intelligent Octopus Go and E.ON Next Drive Smart, are EV tariffs: both require a qualifying electric vehicle or a supported smart charger before you can join, whatever your heating system. If you have no EV, that rules two of the four out before you get to comparing rates.

The four tariffs, checked today

Rates and windows checked directly against each supplier's own tariff page on 25 September 2026. Octopus Cosy's cheap and peak rates are set as a percentage of your own region's day rate rather than a fixed pence figure, so the exact pence amount you pay is postcode-specific; British Gas Heat Power's discount works the same way, as a percentage off your own unit rate. Standard variable is the Ofgem price cap for 1 October to 31 December 2026, confirmed 26 August 2026.

What the discount is actually worth, worked through

Neither Octopus nor British Gas publishes Cosy's or Heat Power's discount as a flat pence figure, because both are set as a percentage of your own regional day rate. Taking the 26.32p average capped rate as a stand-in for a typical variable day rate (your own day rate will differ slightly by region and supplier), a 51% discount puts Cosy's three cheap windows at roughly 12.9p per kWh, and its 16:00 to 19:00 peak, 50% above that day rate, at roughly 39.5p. Moving a kilowatt-hour of heating or hot water into a cheap window instead of paying the standard capped rate saves you around 13.4p on that unit; running the heat pump hard through the 4pm to 7pm peak instead costs you around 13.2p more than standard. British Gas Heat Power's 50% discount, on the same stand-in rate, works out to roughly 13.2p for the discounted hours, credited back on your bill afterwards rather than billed lower upfront.

These are illustrative figures built from the published discount structure and the current capped average rate, not a quote. Cosy's and Heat Power's actual day rates are set regionally and change with supplier repricing, so confirm the live rate on your own account before treating either as a fixed saving.

Why the discount depends on when your heat pump actually runs

A heat pump with a buffer tank or hot water cylinder can be scheduled to pre-heat during a cheap window and coast through the peak on stored heat. One without any thermal store tends to run in response to the room thermostat, which for most households means it works hardest in the early morning and again in the evening, exactly when Cosy's peak sits. That is the practical catch with any tariff built around fixed windows: the saving is real, but it depends on your system's ability to shift load into the cheap hours rather than simply running whenever the house calls for heat.

British Gas Heat Power: the same idea, a different mechanism

Heat Power's discount lands as a weekly bill credit rather than a lower unit rate charged at the time, which changes the practical experience but not the underlying arithmetic: electricity used inside the roughly 70 discounted hours a week is billed in full and then half of it comes back as credit. It needs a British Gas electricity account and Direct Debit, and it is not available on a prepayment meter. Like Cosy, the discount is set against your own unit rate rather than published as a flat pence figure, so the same caution about regional variation applies.

The two that need an EV, whatever your heating system

Intelligent Octopus Go and E.ON Next Drive Smart both publish rates that beat Cosy and Heat Power on paper, 8p to 8.5p per kWh against roughly 12.9p to 13.2p, and both apply their off-peak window to the whole home, not just a car. Neither will let you open an account without a qualifying EV or a supported smart charger on the same tariff, because the products are built, priced and regulated as EV tariffs. A heat-pump-only household cannot join either one to get at the whole-home window, whatever the pence-per-kWh figure suggests.

Intelligent Octopus Go is also mid-change: its published off-peak rate is 8.4p per kWh until 30 September 2026, dropping to 8p from 1 October 2026, both figures taken directly from Octopus's own tariff page as checked today. E.ON Next Drive Smart is fixed at 8.5p for 12 months from when you join; some third-party comparison sites still show an older 8p figure for this tariff, which is out of date against E.ON's own current page.

If you also have solar, a battery, or both

Cosy's three windows, and the pattern behind Heat Power, work the same way a battery-charging strategy does: buy cheap, use later. Our off-peak tariffs and battery charging guide covers the wider set of windows built for a home battery, and choosing a tariff with solar, battery and EV covers what changes once more than one technology is competing for the same cheap hours. A heat pump, a battery and solar on the same roof usually make the tariff decision more valuable, not less, because more of the home's load can be shifted into the cheap window at once.

Tariff rates, windows and eligibility conditions were checked directly against each supplier's own tariff page on 25 September 2026. Suppliers reprice and change eligibility rules without much notice; confirm the current position before switching.