Facts last checked 17 September 2026
The short answer
A new combi boiler, supplied and fitted, costs £1,895 to £3,195 on Smart Energie's four fixed-price tiers in September 2026, the same price wherever you live. That covers a combi replaced with a combi in the same place, and includes the boiler, the manufacturer's own system filter, a full chemical flush, a Boiler Plus compliant smart control, a standard flue up to 1 metre and removal of your old boiler. Converting a system boiler to a combi adds +£795, a regular boiler +£995 and a back boiler +£1,150. For national context, the Energy Saving Trust puts the average cost of replacing a gas boiler at around £3,500.
How much does a new boiler cost in 2026?
For a straight swap, where you have a combi boiler now and the new one goes in the same place with a standard wall flue, the price is set by the tier you choose. The tiers are ordered by the length of the manufacturer guarantee and the boiler ranges behind it, and every tier includes the same fitting, flush, filter and controls.
| Tier | Fixed price | Manufacturer guarantee | Our workmanship warranty | Boiler ranges |
|---|---|---|---|---|
| Essential | £1,895 | 5 years | 2 years | Worcester Bosch Greenstar 1000, Worcester Bosch Greenstar 2000, Glow-worm Betacom4, Baxi 400 Combi 2 |
| Assured | £2,195 | 7 years | 2 years | Ideal Logic+, Baxi 600 Combi 2, Glow-worm Energy |
| Advanced | £2,695 | 10 years | 3 years | Worcester Bosch Greenstar 4000, Ideal Logic Max, Vaillant ecoFIT pure, Vaillant ecoTEC plus, Baxi 800 Combi 2, Glow-worm Ultimate3 |
| Signature | £3,195 | 12 years | 5 years | Ideal Vogue Max, Worcester Bosch Greenstar 8000 Style |
Gas boilers do not qualify for the 0% VAT rate that applies to heat pumps, solar panels and insulation, and there is no government grant for a gas boiler. HMRC's VAT notice lists energy-efficient boilers as standard-rated.
The fastest way to see which tier fits your home, with any extras added, is to get your fixed price in about three minutes. You answer a few questions about your home and the boiler you have now, and the tool shows the total, not a starting figure.
What is included in the price, and what is not?
A boiler price only means something once you know what sits inside it. These items are in every fixed price in the table above:
- The boiler, supplied and fitted by a Gas Safe registered engineer
- A standard horizontal flue up to 1 metre
- The manufacturer's own system filter, the part the guarantee depends on
- A full chemical flush, cleanse and inhibitor to BS 7593
- A Boiler Plus compliant smart control, with automation and optimisation, or weather compensation where the boiler supports it
- A carbon monoxide alarm
- New isolation valves and gas cock where needed
- Condensate run to a suitable existing drain, up to 3 metres inside
- Removal, recycling and disposal of your old boiler
- Benchmark commissioning and handover
- Gas Safe Building Regulations notification
- The manufacturer guarantee registered in your name on the day
- Floor protection, dust sheets and clearing up
- Making good the wall behind the old boiler to a workable standard
- A shock arrestor where there is a water meter
- A scale reducer in hard-water areas
- Parking, congestion and ULEZ charges inside London
- At least 2 years' Smart Energie workmanship warranty (3 at Advanced, 5 at Signature)
These are not in any price, and are quoted separately if your home needs them:
- Asbestos survey, testing or removal
- Access equipment above ladder height, such as scaffolding or towers
- Gas supply work beyond the boiler, such as meter upgrades or a larger supply pipe beyond 3 metres
- Buried or concealed pipework that needs floors, walls or ceilings opened
- Chimney lining or capping when a back boiler is removed
- A full powerflush where a chemical cleanse cannot recover the system
- Replacement radiators, valves or cylinders
- Electrical work beyond the boiler's own fused spur
- Making good beyond a workable standard: no plastering, tiling, decorating or flooring
| Extra | Price |
|---|---|
| Reconnect your existing smart control | No charge |
| Thermostatic radiator valve, each, fitted the same visit | £42 |
| Deep powerflush | £225 |
| Automatic filling loop | £89 |
| Upgraded 28mm magnetic filter, for systems over 13 radiators | £75 |
| Flue extension, per metre beyond the first | £85 |
| Flue guard | £45 |
| Condensate pump, where there is no gravity drain | £145 |
| Landlord gas safety certificate (CP12), with an install | £59 |
| Additional carbon monoxide alarm (the first is included) | £29 |
| Radiator replacement, like-for-like size, fitted the same visit | From £145 |
If we find work outside the price, we stop, price it in writing and wait for your approval. If you decline, we leave the system safe and refund your deposit, less the call-out.
How much extra for a conversion, moving the boiler or a longer flue?
These are the things that most often change a boiler price, and they are worth understanding before you compare quotes. Each amount is added to the tier price, and is the same at every tier.
| Situation | Extra cost |
|---|---|
| Combi to combi, same position | Included |
| Boiler moved within the same room | Included |
| Boiler moved to another room on the same floor | +£175 |
| Boiler moved to a loft or garage | +£350 |
| Floor-standing boiler replaced with a wall-mounted one | +£250 |
| System boiler replaced like for like, cylinder kept | +£295 |
| Regular boiler replaced like for like, tanks kept | +£345 |
| Regular boiler converted to a system boiler, loft tanks removed | +£645 |
| System boiler converted to a combi, cylinder removed | +£795 |
| Regular boiler converted to a combi, cylinder and tanks removed | +£995 |
| Back boiler behind a fire converted to a combi | +£1,150 |
| Converted combi moved to a new position (not where the old boiler was, or the airing cupboard) | +£850 |
| Vertical flue through the roof | +£395 |
| Plume kit, flue within 30cm of a window or door | +£85 |
| Boiler 1 to 2 metres from an outside wall | +£195 |
| Boiler 2 to 3 metres from an outside wall | +£425 |
| Boiler more than 3 metres from an outside wall | +£675 |
| Second bathroom or separate shower | +£150 |
| Third bathroom or shower | +£195 |
| Five or more bedrooms | +£400 |
| 14 to 16 radiators | +£150 |
| 17 to 19 radiators | +£400 |
| LPG instead of mains gas | +£425 |
Why a conversion costs more. A system or regular boiler heats water into a hot water cylinder, and a regular boiler also relies on cold water tanks in the loft. Swapping to a combi means draining and removing the cylinder, taking out or capping the tanks and their pipes, and re-piping the hot and cold water so it runs straight from the boiler. A back boiler sits behind a fireplace, so removing it involves the fire, the old flue and the pipework in the chimney breast, which is why it is the most involved job.
Why moving the boiler costs more. New gas pipe, new heating pipework and a new condensate drain all have to reach the new position, and a new flue route has to be made through the wall or roof. The further the move, the more of that there is.
Some jobs are never priced online, because a surveyor has to see them first: a flat or apartment above the second floor; first-time central heating, a new gas supply, an extension or a new build; four or more bathrooms, or 20 or more radiators; commercial property, a large HMO, or a listed building.
Do you need a combi, system or regular boiler?
A combi heats water on demand with no cylinder, so it suits most homes with one or two bathrooms and saves the space a cylinder takes. A system boiler stores hot water in a cylinder, which suits bigger households drawing hot water from several taps at once. A regular boiler also stores hot water but needs tanks in the loft, and the Energy Saving Trust notes it is unlikely to suit a flat.
One point is easy to miss. The Energy Saving Trust points out that most heat pumps work with a hot water cylinder, so if you remove your cylinder to fit a combi now, you may need to put one back if you switch to a heat pump later. If a heat pump is on your horizon, keeping the cylinder can be the better call. Our guide to combi vs system vs regular boilers goes into this properly.
How do you pay for a new boiler?
You pay 25% when we confirm your price, and the balance when the boiler is working and you have seen it working. Debit card, credit card or bank transfer. We do not sell credit: the price you see is the whole price.
We confirm your price from a few photos before you pay anything. If the confirmed price is higher than your online price, you can walk away having paid nothing.
What must a new boiler come with, and what will it cost to run?
In England, the Boiler Plus standards (in force since April 2018) require every new gas boiler to have an ErP efficiency of at least 92%, and every gas system to have a timer and a room thermostat. When a combi is fitted, one extra efficiency measure is also required: flue gas heat recovery, weather compensation, load compensation, or smart controls with automation and optimisation.
Heating and hot water make up over half of what a household spends on energy, according to the Energy Saving Trust, which is why efficiency matters. Modern condensing boilers reuse heat from the flue gases that older boilers waste. If your current boiler has a metal flue and no plastic condensate pipe running to a drain, it is probably not a condensing boiler, and a replacement should use noticeably less gas. Gas is capped at 7.33p per kWh from 1 July to 30 September 2026, rising to 7.97p from 1 October (Ofgem, Direct Debit, GB average).
Would a heat pump be better value than a new boiler?
Sometimes, and it is worth checking before you commit to another gas boiler. The Boiler Upgrade Scheme gives £7,500 towards an air source heat pump if you own your home in England or Wales and are replacing gas, oil, LPG or electric heating. The Energy Saving Trust describes heat pumps as more than three times as efficient as gas boilers.
The honest catch is the price gap between the fuels. Electricity is capped at 26.11p per kWh against 7.33p for gas (July to September 2026), roughly 3.6 times the price. So a heat pump's running cost is close to a gas boiler's, and better or worse depending on how well it is designed and how warm your home stays. A heat pump makes most sense when your boiler is failing anyway, your home is reasonably well insulated, and you plan to stay. A new boiler still makes sense if you need heat quickly, are moving soon, or your home needs insulation work first.
You can check your grant eligibility in a couple of minutes, or read what an air source heat pump installation involves.
How do you spot a poor-value boiler quote?
- No survey and no questions. A price given without asking about your current boiler type, flue position, bathrooms or water meter will change later.
- Vague inclusions. "A modern efficient boiler, fully installed" tells you nothing. You should see the make, model and output, and whether the filter, the controls, the flush, the flue and old boiler removal are included.
- No named warranty. Ask how many years, whether it is registered in your name, and what servicing it needs.
- No Gas Safe number. By law every gas engineer working in the UK must be Gas Safe registered. Ask to see the engineer's Gas Safe ID card, check the photo, the business name, the expiry date and the qualifications on the back, and check the seven-digit licence number on the Gas Safe Register website. If they cannot show a valid card, do not let them start. Smart Energie's Gas Safe registration number is 921521.
- A low headline that grows. A "from" price with the flue, filter and controls added later often ends above a fixed price that included them.
- Pressure to sign today. A fair price is still fair next week.
When you are ready, get your fixed price in about three minutes. It shows the boilers that suit your home and every extra that applies, itemised.
Common questions
How much should I pay for a new combi boiler?
For a like-for-like combi swap, our fixed prices run from £1,895 to £3,195 depending on the tier, and the Energy Saving Trust gives £3,500 as the national average for replacing a gas boiler. Conversions, relocations and longer flues add to that.
Is there a grant for a new gas boiler?
No. The Boiler Upgrade Scheme pays £7,500 towards a heat pump, not a gas boiler, and gas boilers are charged at the standard VAT rate. If you want grant funding for your heating, a heat pump is the route to look at.
Why does converting to a combi cost extra?
Because the old hot water cylinder, and with a regular boiler the loft tanks, have to be removed and the pipework redone so hot water comes straight from the boiler. On our fixed prices that is £795 extra from a system boiler, £995 from a regular boiler and £1,150 from a back boiler.
What size boiler do I need?
For a combi, size it to your hot water demand rather than the number of bedrooms. One bathroom is usually well served by a 25kW combi, two bathrooms by a 30kW model, and several showers at once by a 32kW model or a system boiler with a cylinder. A survey confirms it.
Do I have to have a smart control with a new boiler?
Not necessarily. In England every gas boiler needs a timer and room thermostat, and a new combi needs one extra efficiency measure, of which smart controls with automation and optimisation are one option. We include a Boiler Plus compliant smart control in every boiler price.
How often does a new boiler need servicing?
Once a year. Manufacturers make an annual service by a Gas Safe registered engineer a condition of their warranty, so missing it can void a 10 or 12 year guarantee.
Should I repair my old boiler instead?
It depends on the age of the boiler, the cost of the repair and how reliable it has been. Our guide on whether to repair or replace a boiler walks through how to decide.