You are quoted against an online fixed price
A website offered them a boiler installed for £1,995 with no site visit. You are pricing a system conversion, a cylinder and a power flush. Without a breakdown the two look like the same job.
For heating engineers
Heating estimates written at the airing cupboard door
A boiler quote is a specification, not a price. Which appliance, which controls, what happens to the old vented system, who notifies Building Control. Talk it through the way you worked it out on site and get a document that answers all of it.
Why estimating is the worst part of the week
The controls conversation happens three times
S-plan, weather compensation, smart stats. You explain it on the doorstep, again on the phone and again on the day, because none of it is written down anywhere.
Registration, notification and warranty paperwork is invisible
The G3 ticket, the Building Control notification and the manufacturer registration are all things the cheap quote is not doing, and none of it shows up in a total.
A real example
System boiler and unvented cylinder upgrade, four-bed detached
On the left is what you would actually write down. On the right is what your customer receives.
Your notes
4 bed detached. old open vent baxi, F&E tank in the loft, gravity hot water, the lot. going system boiler, vaillant ecotec plus 630, 210 litre unvented cylinder in the airing cupboard, i have the G3. strip the F&E out, cap the vent and cold feed. S plan plus, two port valves, wiring centre, cylinder stat. 9 rads all getting TRVs, two need moving because of where their new furniture is going. mag filter and a scale reducer, waters like concrete round here. flue goes vertical through the roof, ill do the flashing kit myself. power flush the whole system before the new boiler goes on, 9 rads. commissioning, benchmark, manufacturer registration, building control for the unvented. 4 days, two of us. warn them about the water being off most of day 2
The estimate
| Item | Qty | Amount |
|---|---|---|
| Vaillant ecoTEC plus 630 system boiler, supplied | 1 each | £1,480.00 |
| 210 litre unvented cylinder with kit, supplied | 1 each | £980.00 |
| Installation labour, two engineers | 4 day | £2,240.00 |
| Remove F&E tank, cap vent and cold feed, make good loft | 1 job | £260.00 |
| S-plan plus controls, two-port valves and wiring centre | 1 job | £480.00 |
| Vertical flue run and roof flashing kit | 1 each | £340.00 |
| Power flush existing system, nine radiators | 1 job | £620.00 |
| Thermostatic radiator valve, supplied and fitted | 9 each | £378.00 |
| Relocate radiator, including pipework alterations | 2 each | £330.00 |
| Magnetic filter and scale reducer, supplied and fitted | 1 job | £260.00 |
| Commissioning, Benchmark, G3 and Building Control notification | 1 job | £180.00 |
| Total before VAT | £7,548.00 | |
An illustration using typical UK rates, not a price list. TradeScribe prices from the rates in your own notes and your saved day rate.
What we know about heating estimates
These are the lines that come up again and again on a heating engineer's estimate. Mention any of them in your notes, however briefly, and they come out properly worded.
- Combi boiler swap, like for like
- Conversion from open vent to sealed system
- System boiler and unvented cylinder installation
- Power flush, per radiator or per system
- Thermostatic radiator valves, supplied and fitted
- S-plan or Y-plan controls upgrade
- Smart thermostat, supplied and commissioned
- Magnetic filter and inhibitor dose
- Radiator moved or replaced, each
- Commissioning, Benchmark and Building Control notification
Heating estimating questions
Should a heat loss calculation be part of my estimate?
It should be a line on it, and increasingly it has to be. Sizing a boiler off the number of bathrooms is how houses end up with a 35kW appliance cycling all winter. Charging separately for a room-by-room heat loss calculation also gives you something concrete to point at when a customer compares you against an online fixed price that involved nobody visiting the house.
Do I need to list my Gas Safe number on a heating estimate?
There is no legal requirement, but leaving it off costs you work. It is the one detail a cautious customer can verify in thirty seconds on the register, and it quietly separates you from an unregistered installer. Put the registration number and your G3 qualification in the footer if the job involves an unvented cylinder.
Is a boiler installation zero-rated under the energy-saving materials rules?
No. The zero rate for energy-saving materials covers things like insulation, solar panels, heat pumps and certain controls when installed with qualifying measures, and it runs to March 2027 before reverting to 5%. A standard gas boiler replacement is not on the list and is charged at 20%. Customers read headlines about the relief and assume it applies to everything, so it is worth a sentence in the estimate.
How do I quote a boiler swap when I cannot see the state of the system?
Price the appliance and the installation firmly, and treat the existing system as a separate, conditional item. State that a chemical cleanse is included, that a full power flush is available at a stated price, and that the warranty terms of most manufacturers require the system to be cleaned. That way the customer chooses knowingly rather than feeling upsold on day one.
Should I quote a fixed price or a day rate for heating work?
Fixed for installations, day rate for fault finding and repairs. A customer accepts a day rate happily when the outcome is genuinely unknown, and resents it on a job you have done fifty times. Mixing the two in one document works well: fixed installation, plus an hourly rate clearly stated for any additional work they approve.
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