Boilers
How do I choose a boiler installer — and what should a good quote include?
3 min read · Last updated · Reviewed for accuracy before publishing
Start with the non-negotiable: the engineer must be Gas Safe registered, and you're entitled to see the card. Beyond that, the difference between a good installer and a cheap headline is what's written down. A proper quote is fixed, in writing, and spells out the boiler and flue, a full system flush (not a rinse), a filter, controls set up and explained, making good, removal of the old boiler, the warranty length and what keeps it valid, and any finance terms in full. If a quote is vague on those — or the price seems too good — that's usually because something on that list is missing.
The floor: Gas Safe and insurance
The HSE says anyone employed to work on gas appliances in domestic premises must be a Gas Safe registered engineer — ask to see the card and check the licence number online, by text to 85080 or on 0800 408 5500. Alongside it, ask about insurance and who stands behind the work. This is the baseline, not the selling point.
What a real quote spells out
The specific boiler and flue, a genuine system flush and a filter, controls configured and explained, the old boiler taken away, making good afterwards, the manufacturer warranty length and its conditions, and any 0% finance terms in full, all in writing.
Baxi, for example, requires registration within 30 days and a yearly service to keep its warranty valid. Everything on paper, fixed, before you commit — so 'while we're here' extras can't appear.
The tell of a cheap headline
A very low number usually means a small budget boiler, no flush, no filter, skipped commissioning paperwork (which can void your warranty claim), or a day-rate that balloons on the day. Compare what's included, not just the figure at the top — iHeat's fitted prices start at £1,945, yet its August 2026 installs averaged £2,820. The cheapest quote and the best-value quote are rarely the same one.
“Gas Safe is the floor, not the finish. The real test of an installer is what is written on the quote — the flush, the filter, the warranty conditions, all of it, before a tool comes out.”
Sources
- HSE — Gas safety: home owners and occupiers ("Anyone employed to work on gas appliances in domestic premises must be a Gas Safe registered engineer"; the engineer's competencies are marked on the back of their Gas Safe ID card; accessed 19 Oct 2026)
- HSE — Check an engineer (look an engineer up online by the licence number on their ID card, text "Gas" and the seven-digit number to 85080, or phone 0800 408 5500; accessed 19 Oct 2026)
- Baxi — warranty terms (register within 30 days of installation or commissioning; an annual service in line with the instructions keeps it valid; verified 27 Oct 2026)
- iHeat — New boiler costs (fitted prices from £1,945 including VAT for a combi; average installation £2,820 including VAT in August 2026, with the middle half between about £2,525 and £3,247; conversions around £4,000; relocation charges £495 to £895; updated 1 Oct 2026; accessed 19 Oct 2026)
David founded Datum after years on the tools across heating and plumbing. He writes the boiler and cost guides from what actually happens on real installs.