Why is your heating bill so high in the UK?

High heating bills have four causes, and the fix is different for each. Most people look at one (usually the tariff) and miss the other three. In the typical UK home, doing nothing about three of the four is the difference between a £1,500 winter and a £2,500 winter. This guide walks through each cause, what it typically costs you per year, and the order to fix things in.

The four causes

Most of a high bill comes from one or more of:

1. Tariff. You are paying more per unit than you need to.
2. Fabric. Your home loses heat faster than it should.
3. Heat source. Your boiler or heater is inefficient or badly matched to the home.
4. Fuel type. You are using an expensive fuel.

Each has a typical annual cost of being wrong, and a typical cost to fix. Go in the right order and you save the most money for the least effort.

Cause 1: the tariff you are on

Symptom: your standing charge is high (£500 to £700 a year for the two fuels combined) and your unit rate is at or near the Ofgem cap. If you have not switched in 18 months or more, this is almost certainly you.

Typical annual cost of being wrong: £150 to £300, more if you have an EV or heat pump and are not on a time-of-use tariff.

The fix: switch. If you have a smart meter and an EV or heat pump, the cheapest tariffs right now are Intelligent Octopus Go, Cosy Octopus, and OVO Charge Anytime. For EV-only households, Intelligent Octopus Go gives six hours of 8p per kWh overnight electricity for the whole home. If you do not have a smart meter, request one; most suppliers now book the install within 4 to 8 weeks.

What to watch for: be careful of fixed tariffs that look cheap today but lock you in above the cap if prices fall. As a rule, for 2026, flexible tariffs with a low-price window beat fixed headline rates for anyone with a smart meter.

Cause 2: the fabric of your home

Symptom: you heat the house for hours each evening and it is cold within 90 minutes of the heating going off. You can feel a draught at the window frames or near the loft hatch. You can see condensation on single-glazed or poorly-sealed windows.

Typical annual cost of being wrong: £200 to £600 depending on the home. For a pre-war solid-walled terrace with no loft insulation, it can be higher.

The fix, in order of cost:

• Draught-proof doors and windows. Weatherstripping is £20 a pack; a weekend of work. The measurable reduction in heat loss is often 5 to 10 per cent. Obvious quick win.
• Loft insulation. If you have less than 270mm of mineral wool, top it up. Material cost £200 to £400 for a typical house; one Saturday of DIY or one tradesperson day. Payback is usually under two heating seasons.
• Cavity wall insulation if your walls have a cavity and it is not already filled. Typical cost £500 to £1,500 and it is grant-eligible under ECO4 and the Great British Insulation Scheme for households that qualify.
• Solid wall insulation (internal or external) for pre-1930s homes. The big one. £8,000 to £20,000. Grants available. Payback years, but also the move that makes a heat pump viable.

You get 80 per cent of the fabric savings from the cheaper steps. Start there.

Cause 3: the heating system

Symptom: your boiler is over 15 years old, or shorter cycling with visible noise, or the TRVs on most radiators are stuck or painted over. Your upstairs is boiling when downstairs is cold.

Typical annual cost of being wrong: £150 to £400. Old non-condensing boilers run at 75 to 80 per cent efficiency. A modern A-rated condensing boiler is 88 to 92 per cent in real-world use.

The fix:

• Service the boiler annually. £80 to £120. Catches bad combustion, low water pressure, and a heat exchanger slowly furring up.
• Replace failing TRVs. £15 to £25 per valve, 15 minutes each for a plumber. Instantly fixes the "upstairs too hot, downstairs too cold" problem.
• Balance the radiators. Free. Most installers will do it at a service.
• Consider a boiler replacement if yours is pre-2005 and you have no BUS-eligible heat pump plans. A new 92 per cent boiler saves £100 to £200 a year versus a G-rated unit. If you are moving to a heat pump within three years, skip the boiler replacement and run the old one out.

Cause 4: the fuel

Symptom: you are on oil, LPG, or old electric storage heaters. Your bill is wildly variable and you worry about running out.

Typical annual cost of being wrong: the most expensive of the four. An oil household pays £1,500 to £2,500 for heat. An LPG household pays similar. An old electric storage heater household on a standard tariff can pay £2,500 to £3,500.

The fix: a heat pump is usually the right answer, with the Boiler Upgrade Scheme paying £7,500 of the install. Running cost drops 30 to 60 per cent. Payback on the net install is 3 to 6 years for oil and LPG, and usually under 3 years for old electric heating. The honest exception: if your home is badly insulated, fix the fabric first and treat the heat pump as step two.

Our guide on whether a heat pump is worth it in 2026 goes into each situation with the numbers.

A rough diagnosis

Take a second to put yourself in a bucket. If your home is:

• Average insulation, mains gas, modern boiler, default tariff: your main cost is the tariff. Switch. £150 to £300 a year saved.
• Poor insulation, any fuel: fabric is your main cost. Weatherstripping, loft insulation, then consider cavity walls. £200 to £600 a year saved.
• Average insulation, old boiler, mains gas: the boiler is probably costing you £100 to £200 a year you do not need to spend.
• Off mains gas (oil, LPG, old electric): the fuel is the main cost. Look at a heat pump with the BUS grant. £800 to £1,800 a year saved.

The things that add up fastest are the ones that do not require you to spend thousands.

Quick wins (same week)

• Switch to a smart TOU tariff if you have a smart meter. 30 minutes online.
• Draught-proof your obvious cold spots. One Saturday.
• Set your thermostat to 19 degrees, not 22. £50 to £90 a year saved and you get used to it within a fortnight.
• Lower boiler flow temperature to 55 to 60 degrees. Works on every condensing boiler. 5 to 10 per cent saving for zero cost.

Medium-effort wins (same year)

• Top up loft insulation.
• Replace stuck TRVs.
• Get the boiler serviced if it has been more than 12 months.
• Install a smart thermostat with schedules. Around £200 installed; 10 per cent saving in most homes.

Big moves (multi-year)

• Cavity or solid wall insulation if appropriate.
• Window upgrades (usually not payback-positive on their own, but worth it at end-of-life).
• Heat pump with BUS grant if you are off-gas, or if you are on gas with good insulation and expecting to replace the boiler within five years anyway.
• Solar plus battery plus smart tariff, if the EV and heat pump are in the plan.

The calculator on this site works out the combined numbers for your home, including which of these three "big moves" pays back fastest given your situation.

FAQ

I have switched tariff. Why is my bill still high?

Two reasons. Either the rest of your setup (fabric, heat source, fuel type) is the bigger cost and the tariff move only recovered £200 of a £1,500 problem, or the new tariff is fixed at a rate that was competitive six months ago but is no longer. Check what the current best tariff looks like for your usage pattern, and look at fabric as the next step.

Is gas really cheaper than electricity for heating?

Yes, at per-kWh prices. Mains gas is 6.72p per kWh in April 2026; electricity is 24.67p per kWh. A 92 per cent gas boiler delivers 6.72 / 0.92 equals 7.3p per kWh of heat. A heat pump at SCOP 3.2 delivers 24.67 / 3.2 equals 7.7p per kWh. Close but gas wins at headline rates. The gap closes entirely on a TOU tariff where some of the heat pump's work happens off-peak.

Should I replace my boiler or install a heat pump?

If your current boiler is under 10 years old and working, run it to end of life. If it is over 15 years old and you are on gas with good insulation, get heat pump quotes alongside boiler quotes and compare the 10-year total cost. If you are off-gas, the heat pump is usually the right answer now.

Will a smart thermostat save me money?

Yes, but less than people claim. Realistic saving is 8 to 12 per cent in a home where the heating used to be on a dumb timer. If you already heat only when occupied and to a sensible temperature, the saving is marginal.

What is the cheapest heating fuel?

Per useful kWh of heat delivered, mains gas is the cheapest in the UK today at April 2026 prices, followed by heat pumps on a smart TOU tariff, followed by LPG and oil at similar levels, followed by direct electric at the cap. This ordering is policy-sensitive and changes every year.

Ready to see the numbers for your specific home? The calculator will estimate your annual bill, show you where the biggest saving opportunity is, and tell you if a heat pump or solar would pay back. Switching tariff on its own is worth doing today. For the bigger decisions, run the numbers first.