Heat pump tariffs in 2026: how to model your real running cost

One of the things I hear most often from heat pump owners — both happy and unhappy — is a running-cost figure quoted in isolation. "It cost me £1,200 to heat the house this winter." "Mine ran me £2,400." Without context, neither number is interpretable. Without knowing the tariff, the SPF, the heat demand, the schedule, and the season, those numbers are just anecdotes — and anecdotes are how the heat pump conversation gets stuck in the public mind.

The honest framing is that heat pump running cost is a four-variable problem: heat demand, SPF, electricity price per kWh, and how those three interact across the year. Get any one of them wrong and the whole estimate falls apart. The good news is that modelling it properly isn't hard — it just requires you to take the tariff seriously rather than as an afterthought.

This piece walks through what the tariff landscape actually looks like in 2026, how to model your real running cost, and how the relationship between tariff and system controls determines whether you end up below gas-equivalent or considerably above it. Without naming any specific commercial tariff, because the market shifts faster than this article will, the structural patterns are durable.

The tariff landscape in 2026

In 2026 the UK tariff market splits roughly into four families relevant to heat pump owners:

• Standard variable / capped flat-rate tariffs. Single rate (typically 26–28p/kWh in 2026) applied at all times. Simple, predictable, and a poor fit for heat pumps because it gives the system no way to shift load to cheap windows.
• Time-of-use tariffs (general). Two or three different rates by time of day. Typical structure: cheap overnight rate (often 12–17p), standard rate during the day (24–28p), peak rate during the early evening (28–35p). Designed for households with flexible loads — heat pumps and EVs are the obvious ones.
• Heat-pump-specific tariffs. A subset of time-of-use tariffs designed for heat pump households specifically, with cheaper overnight rates and sometimes a heat-pump bonus credit. Typically require an MCS-certified installation and may require specific controls. Currently the best-value option for typical heat-pump households.
• Half-hourly / dynamic tariffs. Wholesale-linked, with prices changing every 30 minutes. Excellent value for households with sophisticated controls and tolerance for variability; less good for households who want a predictable bill.

The structural pattern: anything other than flat-rate gives a heat pump room to shift load and capture cheaper electricity. The savings differ by tariff, but the principle is the same — the system works harder to use the cheap hours.

How to model your running cost properly

The arithmetic is genuinely simple once you have the four variables. Let me walk through it for a typical UK 3-bed semi.

Variable 1: heat demand. Get this from your last gas bill. Convert to kWh of heat using the boiler efficiency (88% for a modern combi, 80% for an older system). For a typical EPC C semi, you'll see 9,000–14,000 kWh of heat demand per year, split roughly 80% space heating, 20% hot water.

Variable 2: SPF. If the system isn't installed yet, assume 3.0 for a typical install in a typical home (the median UK figure). Don't assume more; well-tuned systems hit 3.4–3.8, but assuming the median is the safe planning number. Once the system is installed, measure SPF directly — most monitoring solutions report it.

Variable 3: distribution of heat demand across cheap and expensive hours. This is the variable most analyses skip. A heat pump with a hot-water tank and proper controls can shift maybe 40–60% of its heating into cheap-rate hours. Without controls or with a system that can't run continuously at low flow temperatures, that drops to 10–20%.

Variable 4: tariff structure. Cheap rate, peak rate, standing charge, any export.

Multiply through and you have your running cost. Worked example: 11,000 kWh heat / SPF 3.0 = 3,667 kWh electricity. 50% in cheap rate at 13p (£238) + 50% in standard rate at 27p (£495). Total: £733 for space heating, plus ~£250 for hot water, total £980 for the year. Compare to gas at 6.5p × 12,500 / 0.88 = £924. Roughly equivalent.

Where the marketing-quoted savings actually come from

The £200–£500/year saving figures that get quoted in heat-pump marketing are real but specific. They come from one of three patterns:

1. Time-of-use shift. The same household on a flat tariff would pay more for the heat pump than for gas; on a time-of-use tariff with 50–60% load shift, they pay slightly less. The saving is the tariff structure, not the technology.
2. Heat-pump-specific tariff bonus. Some specialist tariffs offer a credit or cheaper rate specifically for heat pump customers. Worth £100–£250/year on top of the time-of-use saving.
3. SPF tuning over the first heating season. A system that ends year one at SPF 2.8 and year three at SPF 3.4 has improved its running cost by around 20% just through control tuning. That's worth £150–£250/year for a typical house.

Add these together for a household that does all three things and you get the £500+ figure that tops the marketing claims. A household that does none of them — stays on flat tariff, doesn't tune the system, doesn't shift load — sees a heat pump that runs more expensively than gas and concludes that 'heat pumps don't work', which is the wrong conclusion. The technology works; the configuration didn't.

Choosing a tariff: what to look for

Strip the marketing away and what you want from a heat pump tariff is:

• A meaningful gap between cheap-rate and standard-rate prices. If the cheap rate is 22p and the standard rate is 27p, the load-shifting incentive is small. Look for at least 10p gap, ideally 14p+.
• Reasonable cheap-rate window length. A 2-hour cheap window won't let the system fully cycle; a 6+ hour window will.
• Standing charge that you can live with. Some specialist tariffs have higher standing charges to subsidise the cheap rate. Check whether the volume you actually use makes the maths work.
• Peak-rate exposure that is bounded. Some tariffs have very high peak rates that punish a system not properly avoiding them.
• Compatibility with your controls. Some tariffs require specific smart-meter functionality or controls integration to access the best rates.
• Notice / exit terms. The tariff that's best for you in 2026 may not be the best in 2028. Avoid tariffs with long lock-in.

Configuring the system to actually use the tariff

The tariff is half the equation. The other half is the system controls. Even on a well-structured time-of-use tariff, a heat pump that doesn't know how to use the cheap window won't capture much benefit.

What 'using the tariff' actually means in practice:

• Hot water schedule set to fully heat the cylinder during the cheap window, with one optional top-up midday if needed. This alone is worth £80–£150/year.
• Pre-heat the house during the last 90 minutes of the cheap window, lifting setpoint by 1–1.5°C so the building's thermal mass carries it through the morning peak. Worth £60–£120/year.
• Soft setback during the early-evening peak — lower setpoint by 0.5–1°C if the tariff has a peak window. The building coasts and the peak rate is avoided.
• Avoid backup electric resistance heaters during peak hours. Most heat pumps have a backup element for very cold days; ensure it's locked out during peak rate windows.

This level of configuration is rarely the default. It's a manual setup task that the installer or owner does, not something that comes out of the box. Worth doing.

Worked examples for three real-ish UK households

To make this concrete, here are three households I've modelled, with names changed and numbers rounded:

House A — 1980s 3-bed semi, EPC C, family of four: Heat demand 11,500 kWh/year, SPF 3.2 (well-tuned). On a time-of-use tariff with 55% load shift: £860/year for heating + hot water. On flat tariff: £1,100. On heat-pump-specific tariff with bonus: £790. Equivalent gas cost: £960.

House B — Victorian terrace, EPC D, retired couple: Heat demand 13,800 kWh/year, SPF 2.7 (under-spec radiators in two rooms). On time-of-use tariff with 35% load shift (less, because the household is home all day): £1,560/year. On flat tariff: £1,720. Equivalent gas cost: £1,150. The heat pump is more expensive in this case — the SPF is too low and the load profile too inflexible.

House C — 2010s 4-bed detached, EPC B, family of three: Heat demand 8,200 kWh/year, SPF 3.6 (well-specced, well-tuned). On time-of-use tariff with 65% load shift: £490/year. On flat tariff: £640. Equivalent gas cost: £680.

The pattern: where the building is good and the system is well-configured, the heat pump on a time-of-use tariff is cheaper to run than gas. Where the building is weaker or the SPF is depressed, the heat pump is more expensive. The tariff is the lever; the building physics is the floor.

The honest summary

Heat pump running cost in 2026 UK is a tariff problem at least as much as a technology problem. The same physical system — same heat pump, same building, same household — will run anywhere between 60% and 130% of equivalent gas cost depending on the tariff and the controls. That's an unusually wide spread, and it's why the anecdotes you hear vary so dramatically.

The recommendation: when modelling a heat pump, model the tariff first, the SPF second, and the heat demand third. The tariff is the variable that flips the answer. Without time-of-use, most heat pumps run more expensively than gas. With time-of-use and proper controls, most run cheaper. Plan for the controls work — it's where the actual saving lives.

The heat pump running cost conversation has been stuck for years on a false binary — either heat pumps are cheap to run (marketing) or they're expensive (skeptics). The truth is more interesting: they're tariff-sensitive devices that produce different bills for different households depending on the contract and the controls. The technology has been ready for years; the tariff and controls layer is what's been catching up.

If you have a heat pump or are about to, model your real running cost with the four variables above. Pick a tariff that gives you load-shift room. Configure the controls to actually use that room. Tune through the first heating season. Done well, the running cost comes in below gas. Done poorly, it doesn't. The technology isn't the variable. The configuration is.