Boiler Installation
Fitting a boiler where there was not one before, or moving one to a different position.
Boilers
Boilers, from a service to a full replacement
Most UK homes are still heated by a boiler, and most heating questions are boiler questions. Here is what the different types suit, what the common warning signs actually mean, and when it is worth thinking beyond a like-for-like replacement.
The Boiler Upgrade Scheme does not pay for a new gas boiler
This catches out a great many people, and the scheme's name is entirely to blame. The Boiler Upgrade Scheme funds heat pumps, and biomass boilers in limited circumstances. There is no grant under it for installing a conventional replacement gas boiler, whatever the property or the household.
If you are replacing a boiler, this page and the ones below are the right place. If you are open to a heat pump, the Boiler Upgrade Scheme may well be relevant — and we have written a full explanation of why the name causes this confusion.
Boiler services
Four things people usually need, and one page about what drives the price.
Boiler Replacement
Swapping an ageing or failed boiler, including changing between boiler types.
Boiler Repair
Diagnosing and putting right boiler faults, breakdowns and error codes.
Boiler Servicing
Annual servicing to keep a boiler running safely and as efficiently as it can.
New Boiler Cost
What actually drives the price of a new boiler, and why quotes differ so much.
The three boiler types
Choosing between them is mostly a question about hot water, not about heating.
| Type | How hot water works | Suits | The trade-off |
|---|---|---|---|
| Combi | Heats water on demand; no cylinder, no tanks | Smaller homes with one bathroom; properties short of space | Flow rate is shared, so two outlets at once suffer |
| System | Heats a hot water cylinder; most components built in | Homes with more than one bathroom and space for a cylinder | Stored hot water runs out until it reheats |
| Regular (heat only) | Cylinder plus feed and expansion tanks in the loft | Older systems, larger houses, low-pressure setups | Takes the most space of the three |
A combi heats water as it flows through, so there is no cylinder and no tank. That makes it compact and means hot water is effectively unlimited — but the flow rate is shared between outlets, so running a shower and a bath at once is where people notice the limitation.
A system boiler heats a cylinder full of water. Two bathrooms can be used at once at full pressure, which is the main reason to choose one, and the cost is a cylinder taking up space and hot water that runs out until it reheats.
A regular boiler works with a cylinder plus feed and expansion tanks in the loft. It is the traditional arrangement, still common in older properties, and usually retained rather than chosen from scratch.
One point worth knowing if a heat pump is anywhere in your future: removing a cylinder in favour of a combi is the single change that makes a later heat pump hardest, because a cylinder has to be reinstated. It is not a reason to avoid a combi, but it is worth weighing.
Signs a boiler or heating system needs attention
Several of these are system faults rather than boiler faults, which is worth establishing before anyone quotes for a replacement.
- Rooms that never quite get warm
- Often a system problem rather than a boiler problem — sludge, trapped air or a failing pump. Worth diagnosing before replacing anything.
- Losing pressure repeatedly
- Topping up more than very occasionally usually means a leak somewhere in the system or a failed expansion vessel.
- Banging, gurgling or kettling
- Kettling — a sound like a kettle boiling — commonly points to scale or sludge in the heat exchanger.
- Hot water that runs hot then cold
- On a combi, often a diverter valve or a scaled plate heat exchanger. On a stored system, a cylinder or thermostat issue.
- A boiler that keeps locking out
- Repeated fault codes and resets are a boiler telling you something. Note the code — it narrows the diagnosis considerably.
- Rising bills with no change in use
- Efficiency drifts as a boiler ages and as a system fills with debris. A service will confirm whether it is the appliance or the system.
If you smell gas
Do not use switches or naked flames, open doors and windows, turn the supply off at the meter if you can reach it safely, leave the property and call the National Gas Emergency Service on 0800 111 999. That number is a free 24-hour national emergency line.
When it is worth considering a heat pump instead
Not a sales pitch — a list of the situations where the comparison is genuinely worth making before you commit to another boiler.
- You are off the mains gas grid. If you heat with oil or LPG, the running-cost comparison is very different from a mains gas property, and a higher grant value may be available. See the off-gas-grid grant.
- Your boiler is ageing but still working. Choosing calmly is a very different exercise from replacing in an emergency, and a heat pump needs design time.
- You already have a cylinder. One of the more common practical obstacles is already solved.
- You are doing other work anyway. An extension, new flooring or a rewire absorbs a lot of the disruption.
If none of those apply, a boiler is very likely the right answer, and there is nothing wrong with that. Our guide comparing heat pumps and gas boilers is written to be useful in both directions.
Frequently asked questions
Is there a government grant for a new gas boiler?
Not through the Boiler Upgrade Scheme. Despite its name, that scheme funds heat pumps and, in limited circumstances, biomass boilers — not a conventional replacement gas boiler.
How long should a boiler last?
Most domestic boilers are expected to give somewhere in the region of ten to fifteen years of service, with annual servicing. Beyond that, parts availability and efficiency both start to work against keeping it.
Should I repair my boiler or replace it?
A useful rule of thumb: if the repair costs a significant fraction of a replacement, the boiler is beyond its expected life, or it has failed more than once in a season, replacement is usually the better decision. A single fault on a well-maintained boiler is usually worth repairing.
Do I have to have my boiler serviced every year?
It is not a legal requirement for an owner-occupier, but most manufacturer warranties require it, and landlords have separate legal duties in respect of gas safety. It is also how faults are caught while they are still cheap.
Who is allowed to work on a gas boiler?
By law, work on gas appliances must be carried out by an appropriately registered engineer. Always check registration before allowing anyone to work on a gas appliance in your home.
Can I switch from a regular boiler to a combi?
Usually, yes — it frees up the cylinder and tank space. Whether it is a good idea depends on your hot water demand: a household with two bathrooms in simultaneous use is often better served by a system boiler and a cylinder.
Need help with a boiler?
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