The cheapest-looking boiler quote is not necessarily the cheapest complete installation. Compare the same specification, work, controls, protection and paperwork line by line. If an item is unclear, mark it “not confirmed” rather than assuming it is included.

Build one specification before collecting prices

Give every installer the same starting information: current boiler and system type, proposed location, number of bathrooms, known hot-water issues, radiator changes, access constraints and any planned building work. Ask for a site survey before treating a price as final.

The installer should still assess the property independently. A shared brief simply reduces the chance that one quote assumes a like-for-like swap while another includes a conversion or remedial work.

The quote-comparison table

Blank cells are useful: they show what has not yet been promised.

Compare the boiler, not just the badge

Record the exact model and output. Ask what heat-loss and hot-water information supports the choice, and request the model’s minimum as well as maximum output. For a combi, ask how the quoted hot-water performance relates to measured mains pressure and flow.

A higher output is not automatically an upgrade. In England, current building guidance says heating-system specification should be based on an appropriate heat-loss calculation and systems should not be significantly oversized. Requirements differ across the UK, so the installer should explain the rules that apply to the property.

Controls can change both price and result

“Controls included” is too vague. Write down the exact thermostat, programmer, thermostatic radiator valves and any load or weather compensation. Confirm whether existing controls will be reused and whether the installer will configure and demonstrate them.

In England, Boiler Plus requirements apply to boiler work in existing homes. The detailed requirement depends on the boiler and installation, and the other UK nations use their own standards. The quote should identify the proposed controls rather than leave compliance as an unstated assumption.

Cleaning and system protection need a named scope

Quotes may use “flush,” “chemical clean” and “power flush” as if they were interchangeable. Ask what problem has been observed, what process is proposed, and whether filters, chemicals, testing and radiator balancing are included. A more intensive process should have a reason; it should not be inserted or removed solely to make a quote look different.

Also ask how existing sludge, scale, leaks or undersized pipework would be handled if discovered after work begins.

Make variations explicit

The most important sentence in a quote may be the one explaining extra work. Agree:

1. what is included in the fixed price;
2. which assumptions could change;
3. who can approve a variation;
4. how price and schedule changes will be recorded; and
5. whether work pauses until you agree.

Avoid open-ended phrases such as “additional materials charged as required” without a process for approval.

Check the business and the person doing gas work

For gas-boiler work, check the business on the Gas Safe Register and confirm that the individual engineer is qualified for the relevant work by checking the back of their ID card. A logo on a quote or van is not the check.

Request proof of appropriate insurance and clarify whether any electrical, roofing or building work is subcontracted. Record which business accepts responsibility for the complete installation.

Paperwork to list before signing

Depending on the work and jurisdiction, the handover pack may include commissioning records, control instructions, guarantee registration, service requirements, invoices, electrical documents and a Building Regulations compliance certificate. Ask for the exact list that applies to your installation.

Do not release the final payment simply because “paperwork will follow” unless the contract clearly states who supplies each document and when.

A fair way to choose

First eliminate quotes that do not define the outcome. Then compare suitability, completeness, evidence, disruption, guarantee, aftercare and price. A clear mid-priced quote can be better value than a low quote with major exclusions or a high quote padded with unexplained work.

The goal is not to make every quote identical. It is to understand every genuine difference before you choose.

Frequently asked questions

Does the quote include controls and system cleaning?

Only if the items and scope are written down. Ask for exact control models and a named cleaning process, including chemicals, filters, balancing and disposal where relevant.

Who pays for extra work discovered during installation?

The contract should say. Ask for the assumptions, the variation process and the person authorised to approve extra cost before work starts.

Suggested on-page component

Embed the Boiler Quote Comparator directly after the main table. Allow users to rename quotes, mark each item included/excluded/unclear, add their own figures and export their comparison. Do not preload market-average prices.

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