Nobody compares boiler quotes badly on purpose. It happens because the only field guaranteed to appear on all three is the price, so the eye goes there first and the differences underneath never get examined.
The fix is to read them in a fixed order — scope, then exclusions, then compliance, then price. Do it that way and the strongest quote is often not the one you expected.
Read every quote in this order
- 1
Scope: what work is described?
Which appliance, what pipework, what happens to the gas run, is the system cleaned, which controls are included.
- 2
Exclusions: what is explicitly not included?
This is where cheap quotes hide. Gas upsizing, flushing, making good and access equipment are the usual absentees.
- 3
Compliance: what documentation comes with it?
Building Regulations notification, commissioning record, warranty registration, Gas Safe registered engineer details.
- 4
Conditions: what does the warranty require?
Filter fitted, inhibitor dosed, annual service, and in some cases installer accreditation.
- 5
Price and terms, last
Deposit, stage payments, and whether finance is offered. Now the number means something.
Same house, three quotes: what the differences usually are
| Quote | What it typically contains | What that means later |
|---|---|---|
| Cheapest | Like-for-like swap, no system clean, gas run assumed adequate | Risk of poor hot water performance and a warranty claim refused |
| Middle | Swap plus cleanse, filter, inhibitor, controls reviewed | Usually the honest baseline for a straightforward replacement |
| Dearest | Also includes gas upsizing, power flush, new valves, relocation | Either your house genuinely needs it, or the scope is beyond what you asked for |
A dearer quote is only overpriced if the extra items are unnecessary — so ask each installer why the others might have left them out.
Questions that separate quotes quickly
- Did you measure my mains flow rate, and what was it?
- Was the gas supply pipe sized for this appliance, or assumed?
- Is the system being chemically cleansed or power flushed, and why that choice?
- Which boiler output did you calculate, and what was the heat loss figure?
- Who registers the manufacturer warranty, and what does it require of me?
- What documentation will I hold at the end of the job?
What a good quote looks like on paper
It names the appliance and its output. It states what happens to the gas supply, the flue and the condensate. It says which cleaning method is being used and which filter is being fitted. It lists the controls. It sets out what is excluded, and it says which documents you receive.
Length is not the measure of quality, but specificity is. A quote that describes your house rather than a generic installation is a quote from someone who has looked at your house.
Questions people ask
Should I always avoid the cheapest quote?
No — sometimes the cheapest is simply the leanest overheads. Compare scope first; if the scope matches the others and nothing important is excluded, cheap is just cheap.
Is a deposit normal?
Requesting a deposit against the appliance and materials is common practice. What matters is that the terms are written down and the balance is tied to completion.
How many quotes should I get?
Two or three is usually enough to see the pattern. Beyond that the scopes drift so widely apart that comparison gets harder rather than easier.
What if one installer says my gas pipe needs upsizing and another does not?
Ask each to show the calculation or the measured working pressure at full rate. It is a measurable question with one correct answer, not a matter of opinion.
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Compare the work first and the price last. It takes an extra twenty minutes at the kitchen table and it is the single highest-value thing you can do before committing to a boiler installation.
Get a quote you can actually compare
Ours state the appliance, the output, the gas and system work, the exclusions and the documentation, so you can put them alongside anyone else's line for line.