Pricing

How to price a boiler swap

By QuoteSnap·26 July 2026·7 min read

A boiler swap looks like the most predictable job on the board: take the old one off, put the new one on, invoice. It isn't. The margin on a swap is decided before you turn a spanner — on the survey, and on how honestly you priced the system you're hanging a new boiler onto.

Here's a method that holds up. Every figure below is indicative — drop your own rates and current merchant prices in.

Rule one: never price a boiler from a phone call

Customers will try. "It's just a swap, same spot, what's your price?" Give a number on the phone and you own every surprise in that house.

What you need to see before pricing:

The existing boiler — make, model, position, flue route and condition
The gas supply — pipe size from the meter and the run length. An undersized supply is the single most common price-changer on a swap.
The system — open vent or sealed, cylinder or combi, radiator count and condition, pipework material and age
The flue termination — distances to windows, boundaries, openings; whether it's a route you can legally and practically reuse
The condensate route — where it can run to, and whether it's going externally (and therefore needs the right size and lagging)
The electrics — is there a usable fused spur, is the earthing and bonding sound
Access — loft boiler, tight cupboard, third floor flat, parking

A 20-minute survey is what turns a guess into a price. Whether you charge for it is a separate decision — see should you charge for quotes and site visits.

The three jobs hiding inside "a swap"

Price these as separate things, then add them up.

1. The straight replacement. Off with the old, on with the new, same position, reusable flue route, adequate gas supply, sound system. This is your baseline day.

2. The system work the new boiler needs. Modern boilers are less tolerant of dirty systems than the thing you're taking off, and the manufacturer's warranty usually depends on the system being cleaned and treated properly. Realistically that means:

A power flush or a chemical clean, depending on the system's state
A system filter fitted on the return
Inhibitor dosed on refill
Sometimes a magnetic filter plus flush on a system that's been neglected for fifteen years

Don't bury this. It's a real cost, it's a warranty condition, and customers accept it when you explain it as protecting the new boiler.

3. The upgrades that are genuinely optional. New controls or a smart thermostat, TRVs, new radiators, moving the boiler position, a condensate pump. Quote each as an add-on with its own price, so the customer can choose and you don't get talked into doing them free.

Where swaps go over

Surprise	Why it costs	How to handle it
Gas supply too small	New pipe run from the meter, often through the house	Check pipe size and length at survey; price the upgrade or exclude it explicitly
Flue route not compliant	New core, new route, making good	Measure terminal distances at survey, not on the day
Sludged system	Flush, filter, sometimes a rad or two	Test the water, look at the old rads, price a clean in
Asbestos in old flue/board	Work stops	Exclusion on every quote
Cupboard too small for the new unit	Joinery, or a repositioned boiler	Measure the actual model, not "a boiler"
No isolation / seized valves	Drain-down, extra hours	Look at the valves at survey
Loft or awkward position	Boarding, lighting, condensate frost protection	Price access separately

The pattern is the same every time: the ones that cost you money are the ones you could have seen at survey.

Build the price

Labour. Days on site × your real day rate. Most straight swaps are one to one-and-a-half days for one fitter; add half a day for a back-boiler removal, a system conversion, a repositioning or a difficult flue. If you're working with a mate, price two labour rates, not one.
The boiler and kit at cost. Boiler, flue kit, filter, valves, fittings, condensate pipe, electrical bits, chemicals.
Materials markup. You buy it, you carry it, you deal with the warranty claim if it fails. 10–20% is standard.
System work. Flush or chemical clean, filter, inhibitor — as its own line so the customer sees what it's for.
Disposal. Old boiler, cylinder, tanks, packaging. A cylinder and two tanks out of a loft is not a free afternoon.
Certification and notification. Gas Safe registered work must be notified — building regulations compliance for a boiler installation goes through the Gas Safe notification route. Price the admin time.
Contingency. 5–10%, higher on anything pre-2000 or previously altered.

Present it as one fixed price with the optional extras listed separately underneath. Two numbers, not fifteen.

The three-quote problem, and how to beat it

Boiler swaps are the most quote-shopped job in domestic plumbing and heating. Customers get three prices and, if the quotes all look the same, they pick the cheapest. So don't look the same.

What actually wins these jobs:

A named boiler and a named warranty length. "Boiler" versus "Worcester Greenstar, 10-year manufacturer warranty registered on completion" is not the same offer, and price comparison collapses the moment yours is specific.
Saying what's included that theirs won't be. System clean, filter, inhibitor, new valves, disposal, certificate, warranty registration. Half the cheap quotes leave those out and add them on the day.
Two options, not one. A mid-range option and a better one. Customers who are given a choice choose; customers given a single number go shopping.
Speed. The first tidy quote in the inbox is disproportionately likely to win — especially when the customer has no heating and no hot water.

That last one is worth sitting with. When someone's boiler has died in February, they are not running a procurement exercise. They're ringing three numbers and going with the first person who answers and sends something professional. If you're under a floor and can't pick up, that job goes to whoever did — which is the same reason missed calls quietly cost you work.

What to put on the quote

Short, specific, and boring is right:

Boiler make, model and output, and the warranty length with the condition (registered on completion, annual service required)
What's included: removal and disposal, flue kit, system clean, filter, inhibitor, new isolation valves, controls if any, gas safety check, certificate and notification
What's excluded: gas supply upgrade if required, asbestos, plastering/decoration, radiator replacement, upgrading the electrical supply, works to the cylinder unless stated
Provisional sums for anything you genuinely can't know until the old one's off
Payment terms — deposit to secure the boiler, balance on commissioning
Validity — 30 days; boiler prices move

The annual service, quietly

A swap is the start of a relationship, not the end of a job. Put a line on the quote — "Annual service reminder, £X, we'll text you when it's due" — and you convert a one-off into a customer you'll still have in ten years. It costs nothing to add and it's the most profitable line on the sheet.

Boiler quotes are won on speed and clarity, and both are hard when you're on your knees under a sink. QuoteSnap turns a spoken description of the job into a branded, itemised quote — inclusions, exclusions, deposit and terms already there — in about a minute, from the van. Try it free for 14 days.