New boiler cost for a 3 bed semi
The short answer
- £2,300 to £3,500 installed on Heatable's example of a mid-range combi swap; national average for 3 bedrooms about £3,500
- 11,000 kWh of gas a year in a typical 3 bed semi, about £985 with the standing charge
- £190 to £350 a year saved replacing an old non-condensing boiler, a payback of about 5 to 18 years; a condensing one saves about £20
A new gas boiler for a 3 bed semi typically costs £2,300 to £3,500 installed, on the installer Heatable's example of a mid-range combi swap. A typical 3 bed semi burns about 11,000 kWh of gas a year, £985 with the standing charge, and replacing an old non-condensing boiler saves about £190 to £350 a year, so it pays back in about 5 to 18 years. Replacing a boiler that is already condensing saves about £20 a year and does not pay back.
What a new boiler costs for a 3 bed semi
£2,300 to £3,500 installed, on Heatable's example of a mid-range combi swap. The national average for a 3 bedroom home is about £3,500.
| Job | Typical installed cost |
|---|---|
| Heatable's example for a 3 bed semi: a mid-range combi swap | £2,300 to £3,500 |
| Combi boiler, like-for-like swap | £1,800 to £3,500 |
| System boiler, like-for-like swap | £1,800 to £3,500 |
| Regular (heat-only) boiler, like-for-like swap | £1,800 to £3,000 |
| Regular or system boiler converted to a combi | £3,000 to £5,700 |
| National average new gas boiler for a 3 bedroom home | about £3,500 |
Read the detail
Heatable, an online boiler installer, gives £2,300 to £3,500 as its guide price for a 3 bed semi, for a mid-range combi swap. Across every kind of home, its like-for-like combi and system swaps were quoted at £1,800 to £3,500 from January to June 2026, with a median of £2,300 for a standard combi.
Typical installed prices from 2,000 Heatable quotes, January to June 2026, and its example estimates (updated 25 September 2026). Heatable sells and fits boilers itself, so these are one firm's prices, and a local installer can quote more or less. The national average is the DESNZ figure of about £3,500 for a new gas boiler, scaled by home size in our model, which is our assumption.
The national average for a 3 bedroom home is about £3,500: the Department for Energy Security and Net Zero (DESNZ) puts a new gas boiler at about £3,500 including VAT, and our model scales that by home size. The new boiler cost calculator works the cost, saving and payback out for your own home and boiler, and our new boiler cost guide covers what a quote should include and the extras that push a price up.
What a 3 bed semi uses and pays for gas
About 11,000 kWh of gas a year, £985 with the standing charge, in a typical 3 bed semi.
| Home | Gas a year | Gas, energy only | Gas with standing charge | Whole energy bill |
|---|---|---|---|---|
| Typical insulation, around EPC band D | 11,000 kWh | £877 | £985 | £1,885 |
| Well insulated, around EPC band C | 9,350 kWh | £745 | £854 | £1,754 |
| Poorly insulated, around EPC band E | 12,210 kWh | £973 | £1,081 | £1,981 |
Read the detail
A typical 3 bed semi on mains gas uses about 11,000 kWh of gas a year for heating, hot water and any gas cooking. At the price cap of 7.97p per kWh that is £877, or £985 a year with the gas standing charge. It is about 12% more than a 3 bed mid-terrace house (9,800 kWh).
Median gas use for a gas heated home of this type and size, from the DESNZ National Energy Efficiency Data-Framework 2026, as held in our heat model, with the measured difference between EPC bands. Priced at the Ofgem cap for October to December 2026: gas 7.97p per kWh and a standing charge of £108.33 a year by direct debit. The whole bill adds the electricity a 3 bedroom home typically uses.
A new boiler works on the gas column only: it cannot cut the standing charge or the electricity bill, so its saving is limited by how much gas the home burns. Our guide to energy bills for a 3 bed house has the full bill.
What a new boiler saves in a 3 bed semi
£190 to £350 a year replacing an old non-condensing boiler; about £20 if it is already condensing.
| Old boiler rating | Saving with a new A-rated boiler and controls |
|---|---|
| G (under 70% efficient) | £350 a year |
| F (70 to 74% efficient) | £240 a year |
| E (74 to 78% efficient) | £210 a year |
| D (78 to 82% efficient) | £190 a year |
Read the detail
Replacing an old gas boiler with a new A-rated condensing one and better controls saves about £190 to £350 a year in a semi-detached house, according to the Energy Saving Trust, depending on how inefficient the old boiler is.
Energy Saving Trust estimates at July 2026 fuel prices, for a gas heated home fitting an A-rated condensing boiler with a programmer, room thermostat and thermostatic radiator valves in place of an older boiler with a programmer and room thermostat. The Trust's figure is for a semi-detached house of any size; it publishes none by number of bedrooms. These are modelled savings, and they include the new controls.
Measured savings are smaller. Across homes that had a new condensing boiler fitted, whatever it replaced, gas use fell by a median 2.3%: on the 11,000 kWh a typical 3 bed semi uses, about £20 a year. That is the figure to expect if the boiler being replaced is already a condensing one. Our guide to whether it is worth replacing an old boiler explains the gap between the two.
How long it takes to pay back
About 5 to 18 years for an old non-condensing boiler. A working condensing boiler does not pay back on fuel.
| Old boiler rating | On a £1,800 swap | On a £3,500 swap |
|---|---|---|
| G (under 70% efficient) | about 5 years | about 10 years |
| F (70 to 74% efficient) | about 8 years | about 15 years |
| E (74 to 78% efficient) | about 9 years | about 17 years |
| D (78 to 82% efficient) | about 9 years | about 18 years |
Read the detail
On a like-for-like swap at £1,800 to £3,500, a new boiler in a semi-detached house pays for itself in about 5 to 18 years: the short end is a low quote replacing a G-rated boiler, the long end a high quote replacing a D-rated one.
The cost of the swap divided by the Energy Saving Trust's yearly saving for a semi-detached house, the same sum our new boiler cost calculator does. The saving is modelled and includes new controls, so real paybacks tend to be longer.
Viessmann, a boiler maker, says a regularly serviced boiler should last up to around 15 years, which is a fair test of whether the saving comes back in time. Replacing a boiler rated G or F pays for itself inside 15 years even on the £3,500 quote. One rated E or D does so only towards the cheaper end of the price range. On Heatable's £2,300 to £3,500 example for this home, a G-rated boiler pays back in 7 to 10 years and a D-rated one in 12 to 18 years.
A working condensing boiler is not worth replacing for the fuel saving. At the measured £20 a year, a £1,800 to £3,500 swap would take 89 to over 100 years to pay back. If the boiler has failed, the sum is different: you are paying for heating anyway, and the saving is a bonus. If it can be repaired, our boiler repair or replace calculator sets the repair quote against a replacement.
Which boiler type suits a 3 bed semi
One bathroom: usually a combi boiler. Bathrooms, water pressure and heat pump plans decide the rest.
| Your home | Usually suits | Typical output | Why |
|---|---|---|---|
| One bathroom | Combi | 24 to 30 kW | Hot water on demand suits one shower at a time |
| Two bathrooms used at once | System | 18 to 26 kW | Stored hot water runs to several taps together |
| Two bathrooms and no room for a cylinder | Larger combi | 28 to 34 kW | More hot water on demand, though the taps still share one supply |
| A regular boiler with loft tanks, working well | Regular (heat-only), like for like | 18 to 26 kW | Avoids the £3,000 to £5,700 cost of converting to a combi |
| A heat pump planned later | System, keeping the cylinder | 18 to 26 kW | Most heat pumps work with a hot water cylinder |
Read the detail
A 3 bed semi sits on the line between a combi and a system boiler, and the number of bathrooms decides it. Heatable's own rule of thumb is that one bathroom usually suits a combi, two could take either depending on hot water demand, and three or more often make a system boiler the better choice.
Which type suits which home is the Energy Saving Trust's advice. Outputs are the general guides Vaillant and Viessmann publish by bedrooms, bathrooms and radiators, not a specification: the installer's heat loss calculation and your hot water use set the real size.
The output on the label is not the heat the home needs. Our heat model puts the heating load of a typical 3 bed semi at about 9 kW, the size of heat pump it would need. A combi is rated far higher because it has to heat water the moment a tap opens. See what size boiler you need and combi vs system boiler.
How a heat pump compares in a 3 bed semi
A median £12,700 installed, about £5,200 after the grant, so more upfront; cheaper to run only on a heat pump tariff.
| Cost | New gas boiler | Air source heat pump |
|---|---|---|
| Installed | £1,800 to £3,500 for a like-for-like swap | £11,000 to £15,500, median £12,700 |
| After the grant | No grant for a gas boiler | £3,500 to £8,000, median £5,200 |
| Energy a year | £877 of gas | £666 on a heat pump tariff, £937 on a standard tariff |
Read the detail
A heat pump for a typical 3 bed semi costs a median £12,700 installed, about £5,200 after the £7,500 Boiler Upgrade Scheme grant, against £1,800 to £3,500 for a like-for-like boiler swap. It costs more upfront. On a heat pump tariff it then costs about £211 a year less to run than gas; on a standard electricity tariff it costs about £60 a year more.
Heat pump prices are the median and the middle half of what installers recorded under the Boiler Upgrade Scheme for a heat pump of the 9 kW this home needs (DESNZ statistics, August 2026). Running costs use the median efficiency measured in the government's Electrification of Heat trial, at the Ofgem cap for October to December 2026. Gas also carries a standing charge of £108.33 a year, which stops if the gas supply is removed.
Our guide to heat pump cost for a 3 bed semi breaks that price down and covers sizes and running costs in detail.
Our boiler vs heat pump calculator compares the two over 15 years for a home like this one.
New boiler figures for other homes
The swap costs much the same in any home; the saving follows the gas the home burns.
| Home | National average new boiler | Gas a year | Gas bill with standing charge | Old boiler replaced, saving a year |
|---|---|---|---|---|
| 2 bed flat | about £3,200 | 7,100 kWh | £674 | £90 to £170 |
| 2 bed terrace | about £3,200 | 7,000 kWh | £666 | £140 to £270 |
| 3 bed semi | about £3,500 | 11,000 kWh | £985 | £190 to £350 |
| 4 bed detached house | about £3,800 | 14,600 kWh | £1,272 | £220 to £500 |
| 2 bed bungalow | about £3,200 | 9,200 kWh | £842 | £170 to £320 |
Read the detail
The price of the swap changes little from one home to the next. What changes is the gas the home burns, and so what a new boiler can save.
National average: the DESNZ figure of about £3,500 scaled by home size in our model. Gas use and bills from our heat model at the price cap. Savings from the Energy Saving Trust for that type of home, replacing a boiler rated D to G.
Frequently asked questions
How much does a new boiler cost for a 3 bed semi?
Heatable's guide price for this home is £2,300 to £3,500, for a mid-range combi swap. A like-for-like combi or system boiler swap typically costs £1,800 to £3,500 installed, and the national average for a 3 bedroom home is about £3,500.
How much gas does a 3 bed semi use?
About 11,000 kWh a year in a typical gas heated 3 bed semi, which costs about £985 a year with the standing charge at the October to December 2026 price cap.
How much would a new boiler save in a 3 bed semi?
About £190 to £350 a year replacing an old non-condensing gas boiler in a semi-detached house, according to the Energy Saving Trust. Replacing a boiler that is already condensing saves far less: about £20 a year at the measured median.
What size boiler does a 3 bed semi need?
One bathroom: usually a combi boiler of 24 to 30 kW, on the manufacturers' general guides. The installer's heat loss calculation sets the real size. See what size boiler you need.
Is a heat pump worth considering for a 3 bed semi?
It costs more upfront: a median £12,700 installed, about £5,200 after the £7,500 grant. On a heat pump tariff it costs about £211 a year less to run than gas. Our boiler vs heat pump calculator compares the two over 15 years.
Data sources
Heatable quotes and DESNZ for prices, the Energy Saving Trust for savings, our heat model for gas use.
Show every source
- Heatable, New boiler installation costs 2026 (updated 25 September 2026): typical installed prices from 2,000 of its own quotes, January to June 2026, its example estimates by home and its price ranges by brand. Heatable is an online boiler installer, so these are one firm's prices. Checked 5 October 2026.
- Department for Energy Security and Net Zero, Boiler Upgrade Scheme 2026 to 2030 summary business case, footnote 8: a new gas boiler costs about £3,500 including VAT. Other home sizes are scaled from it by our model, which is our assumption.
- Energy Saving Trust, Boiler types explained (last updated 20 May 2026): yearly savings for a gas heated home fitting an A-rated condensing boiler with a programmer, room thermostat and thermostatic radiator valves in place of an older boiler, by the old boiler's rating, at July 2026 fuel prices; £3,500 typical cost of replacing a G-rated gas boiler. Checked 5 October 2026.
- Department for Energy Security and Net Zero, NEED impact of measures data tables 2026: the median fall in gas use in homes that had a new condensing boiler fitted, with and without new heating controls, priced at the Ofgem cap gas rate of 7.97p per kWh.
- Gas use, heating load and energy bills from our heat model, js/heat-model.js, and bill model, js/bills.js: median gas use by type of home and bedrooms from the DESNZ National Energy Efficiency Data-Framework 2026, priced at the Ofgem cap. See our methodology.
- Ofgem, energy price cap for 1 October to 31 December 2026: gas 7.97p per kWh by direct debit.
- Vaillant, What size boiler do I need? (not dated): recommended combi, system and regular boiler output by bedrooms, radiators and bathrooms, given as general guidelines. Read 5 October 2026.
- Viessmann, What size of boiler do I need for my home? (22 March 2022): boiler size by radiators and bedrooms, the heat load of an average home, why an oversized boiler is not recommended, and that a regularly serviced boiler should last up to around 15 years. Read 5 October 2026.
- Heat pump cost from our heat model, js/heat-model.js: the median installed price under the Boiler Upgrade Scheme for a heat pump of the size the home needs (DESNZ statistics, August 2026). EPC points from our EPC calculator model.