New boiler questions answered

These answers cover the questions people ask most before replacing a boiler. They apply to England, where Cheltenham, Gloucester and Tewkesbury are. They are general guidance, not advice on your own home. We read every source on 30 September 2026.

Gas Safe registration

Who can fit a gas boiler? The HSE says anyone paid to work on gas appliances in a home must be Gas Safe registered and competent for that type of gas work ^[S1].

How do I check? Registered engineers carry a Gas Safe Register ID card. The back of the card lists the appliances they are qualified to work on ^[S1]. Enter the licence number from the card into the register's "Check an Engineer" service, and it shows the engineer's photo and qualifications ^[S2]. You can also phone the Gas Safe Register on 0800 408 5500, the number the HSE gives ^[S1]. That is the register's number, not ours. Check whoever quotes you, including the installer we pass your enquiry to.

What if I think my boiler is unsafe? The HSE says it is illegal to use a gas appliance you suspect is unsafe. Turn it off until a Gas Safe engineer has checked it ^[S1].

Building regulations and your certificate

gov.uk lists "install or replace a heating system" as work that may need building regulations approval ^[S3]. You do not need to get approval yourself if you use an installer registered with a competent person scheme ^[S3][S4].

What gov.uk says happens. A scheme installer can self-certify that the work meets building standards, and tells the local authority if needed ^[S4]. The installer gives you a certificate within 8 weeks of the work being finished. It is evidence that the work complies, and it shows up in solicitors' searches when you sell ^[S4].

What the Planning Portal says happens. After the work, the installer should give you a commissioning certificate, for example a Benchmark certificate. They then tell building control, directly or through their scheme. The local authority should later send you a building regulations completion certificate ^[S10].

If the installer is not in a scheme, the Planning Portal says the firm or the householder must tell the local authority in advance and pay a fee ^[S10]. gov.uk warns that without approval you will not have the compliance certificates you may need to sell your home ^[S3]. Emergency boiler repairs do not need approval in advance, but the rules still apply ^[S3].

Condensing boilers. The Planning Portal says replacing a gas boiler will probably mean fitting a condensing boiler, unless there is a good reason one cannot be fitted ^[S10].

Planning permission and flues

The Planning Portal says ^[S5]:

• planning permission is not normally needed to install or replace a boiler when all the work is inside;
• a flue outside is normally permitted development if it meets the conditions. One condition is that it must not rise one metre or more above the highest part of the roof;
• in a conservation area, the flue should not go on the front or side wall if that wall faces a road;
• in a listed building or a designated area, check with the council before fitting a flue. Listed buildings are also likely to need consent for changes inside.

Local rules can add to this ^[S5]. Our area pages cover Cheltenham, Gloucester and Tewkesbury.

Grants

• Boiler Upgrade Scheme. It does not fund a new gas boiler. It pays towards replacing fossil fuel heating with a heat pump or a biomass boiler, in England and Wales, for property owners ^[S6]. For example, it gives £7,500 for an air source heat pump. Hybrid systems, such as a gas boiler with a heat pump, are not eligible ^[S12].
• Energy Company Obligation (ECO). gov.uk says energy suppliers can help with insulation and with "replacing or repairing your boiler" ^[S7]. You may qualify if you are on certain benefits and live in private housing (owners need an EPC rating of D to G, private tenants E to G, with the owner's permission), or if you live in social housing rated E to G ^[S7]. Ofgem says the current phase, ECO4, "will run until 31 December 2026" ^[S8]. We could not confirm whether it is taking new applications. gov.uk warns that installers or agents may contact you directly about ECO. If you are unsure, check with your council or the energy supplier they say they represent ^[S7].
• Great British Insulation Scheme. It has ended. It covered insulation, not boilers, and gov.uk says installations had to finish by 31 March 2026 ^[S11].

Time and cost

Checkatrade says a like-for-like replacement takes about 4 to 6 hours. A regular boiler to combi conversion takes about 1.5 to 2 days, and a system boiler to combi conversion up to about 3 days ^[S9]. Its UK guide (price tables updated March 2026) says a like-for-like combi replacement usually costs £2,500 to £4,000, supply and install ^[S9]. These are national averages. See the cost guide for more figures, or repair or replace your boiler? if your old one is still going.

Servicing

The HSE strongly advises having gas appliances, flues and pipework serviced at least once a year by a Gas Safe engineer ^[S1]. For owner-occupiers this is advice, not a legal duty ^[S1].

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