Things to know
Always put your Gas Safe registration number on the quote itself, beyond your invoice or van signage. Customers increasingly check the register before booking any gas work. Having the number visible on the document they're deciding over is a stronger trust signal than any amount of marketing copy about being "fully qualified."
Manufacturer warranties on boilers are almost always conditional on annual servicing, and that condition is easy for a customer to miss until they need to make a claim. State it plainly: "10-year warranty subject to annual service." It's more than covering yourself. It's the kind of detail that makes a customer trust you enough to book that annual service with you instead of shopping around each year.
A power flush or system clean is easy to skip on a quote and hard to justify afterwards if you do. List it as its own line, with a short explanation that it protects the new boiler from debris circulating from the old system. That turns what could look like an upsell into an obviously sensible part of protecting the customer's new investment.
For system installs, and not swaps alone, state which radiators and pipework are included versus assumed adequate. A customer expecting a full upgrade to every radiator, when the quote only covers the boiler and immediate connections, is the most common source of "that's not what I thought I was paying for" on heating jobs. A one-line scope note prevents it entirely.
Typical heating engineer line items and UK prices
Indicative ranges, excluding VAT. Rates vary by region (London and the South East run higher) and by job size.
| Item | Unit | Typical range |
|---|---|---|
| Combi boiler swap, like-for-like location (fit only) | per job | £900–£1,600 |
| Combi boiler (mid-range, supply) | per unit | £900–£1,800 |
| Power flush (up to 10 radiators) | per job | £350–£600 |
| Chemical flush + inhibitor (BS 7593) | per job | £120–£250 |
| Magnetic system filter | supply + fit | £120–£220 |
| Smart thermostat / weather compensation | supply + fit | £150–£350 |
| Replace radiator (like-for-like) | per radiator | £180–£350 |
| Boiler relocation / new flue routeVaries widely with flue length and route. | per job | £400–£1,200 |
Common heating engineer jobs and how to price them
- Combi-to-combi replacements
- Fixed price covering boiler, controls, flush, filter, commissioning and notification, with warranty years stated.
- System-to-combi conversions
- Fixed price plus clear allowances for removing the cylinder and tanks and for capping redundant pipework.
- Radiator upgrades
- Per-radiator pricing, with balancing the system included.
- Breakdown repairs
- Diagnosis fee plus parts at quoted price; customers appreciate the option to apply the fee to a replacement.
Regulations and certificates to reference
- Gas Safe Register — all gas boiler work must be done by a registered engineer. Your registration number belongs on the quote.
- Boiler Plus (England) — a replacement combi must come with time and temperature controls plus one energy-saving measure — weather compensation, load compensation, smart controls with automation and optimisation, or flue gas heat recovery. Show which one you are fitting.
- BS 7593 water treatment — the system must be cleaned and flushed, with inhibitor added, before a new boiler goes in. Manufacturers often void warranties without it, so price the flush and inhibitor as their own line.
- Benchmark commissioning checklist — completed at handover and needed for most manufacturer warranties. Mention it in the notes.
Payment terms heating engineers commonly use
- Deposit to order the boiler (commonly 20–30%), balance on commissioning.
- Finance customers: note any third-party finance reference on the invoice.
- Breakdown work: payment on the day, parts ordered against payment.
Read more: Invoice payment terms explained · Payment methods to offer clients
VAT and CIS for heating engineers
VAT
Gas boiler installations are standard-rated at 20% — a boiler is not an energy-saving material.
Heating controls (timers, thermostats, TRVs) count as energy-saving materials on their own, but fitted as part of a new boiler installation they're one standard-rated (20%) job — don't zero-rate them on a boiler quote.
Below the £90,000 threshold you can quote without VAT, which is a meaningful price gap on a £2,500+ job.
Construction Industry Scheme (CIS)
Heating installation is within CIS, so a builder or developer who engages you as a subcontractor deducts from the labour part of your invoice. Separate the boiler and materials from labour.
General guidance, not tax advice — check your position with HMRC or an accountant.
Read more: Do I need to charge VAT on my invoices? · What must an invoice include? (UK legal requirements)
What this template includes
- Boiler / appliance model and supplier
- Labour broken out from materials
- Power flush / system clean as own line
- Gas Safe / F-Gas certificate reference
- Warranty period clearly stated
Full guide
How to Start a Heating Engineer Business as a Sole Trader
Frequently asked questions
In England, a new combi boiler must be installed with time and temperature controls and at least one extra energy-saving measure, such as smart controls with automation and optimisation or weather compensation. Name the measure on the quote so the customer sees it is included.
It depends on the system. A heavily sludged system needs a power flush. A cleaner one may only need a chemical flush with inhibitor. Either way, BS 7593 treatment is expected and manufacturers check for it at warranty claims.
State the manufacturer, the warranty years and the conditions (registration within 30 days, annual service, a filter fitted). Customers compare quotes on warranty as much as on price.
You do, through Gas Safe, normally within 30 days. The customer then receives a Building Regulations compliance certificate. Include it as a line so it is clearly part of the price.
Yes — always include your Gas Safe registration number. Customers know to check the register and it's a major trust signal compared to unregistered competitors.
Note that warranty registration with the manufacturer is included, and state any ongoing requirements (e.g., "10-year warranty subject to annual service") so customers know to book service visits.
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