Get comparable written quotes
Citizens Advice recommends getting written quotations from at least three contractors where practical. Give each business the same description of the existing system, hot-water needs, problem rooms, preferred boiler location and any planned changes. A quotation should be a fixed offer for the stated work; an estimate is only a likely cost and can move.
Check that each document names the contracting business, property, quotation date, validity period, VAT treatment and payment schedule. Ask how variations will be priced and approved. If an installer changes the scope after a conversation, request a revised written quotation.
Verify who will do the gas work
Gas work must be carried out by a Gas Safe registered engineer who is qualified for the relevant work. Search the official register for the business and ask who will attend. The engineer's ID card shows the categories of gas work they are qualified to perform; check it when they arrive.
Do not rely solely on a copied badge, an advertising-platform profile or a subcontractor's first name. The quotation should make clear which business holds the contract, who takes payment and who is responsible for the installation and warranty support.
Gas Safe registration is a safety requirement, not a price or customer-service guarantee. Keep the qualification check separate from the commercial comparison.
Compare the equipment and sizing basis
Record the exact boiler make, model, output and warranty rather than accepting a brand family. Ask why the proposed size suits the home's heating and hot-water demand. Bigger is not automatically better, and two installers may have priced different controls, filters, cylinders or system changes.
The quote should state the controls included and how the new boiler will work with the existing heating system. If a flush, filter, inhibitor, radiator valve or balancing task is recommended, have the method and price written into the scope.
- Exact boiler and control model numbers.
- Sizing rationale and any assumptions about occupancy, showers or extensions.
- Filter, flush or cleaning method, inhibitor and system balancing.
- Cylinder, pump, valves, radiators or other heating-system changes.
- Manufacturer and workmanship warranty terms, including registration responsibility.
Use one scope table for hidden differences
The cheapest total may describe the smallest scope. Mark each item included, excluded, provisional or unclear, then send the same clarification questions to every installer.
| Area | What to look for | Why it affects price |
|---|---|---|
| Boiler and controls | Exact models, output, thermostat and zoning work | Different packages can look similar in a headline description |
| Flue and condensate | Route, terminal, plume management, drainage and access | Relocation or difficult access can add labour and materials |
| Heating system | Cleaning, filter, inhibitor, valves, pump and balancing | The condition of the existing system changes the work required |
| Utilities | Gas pipe, electrical, water and any meter or supply responsibility | Upgrades may require another trade or separate charge |
| Removal and finish | Old equipment, waste, holes, boxing, decoration and making good | Finishing work is often excluded unless it is named |
| Compliance and handover | Notification, certificate, Benchmark record, manuals and training | These documents support safe use, records and warranties |
Make compliance and handover explicit
Building work can require approval. In England and Wales, a suitably registered competent person may self-certify covered work instead of the homeowner making a separate building-control application. Ask who will notify the work and which certificate or record you will receive; arrangements differ across UK nations, so check the rules for the property.
Before final payment, expect the agreed commissioning and handover documents, controls explanation, warranty registration evidence and a clear route for defects. Keep the quotation, invoice, certificates and serial numbers together.
- Who is responsible for building-regulations notification or approval?
- Which commissioning record and completion certificate will be supplied?
- Who registers the manufacturer warranty, and by what deadline?
- What aftercare is included and how quickly are faults handled?
Check price, payment and exclusions last
Once scope is comparable, review the total including VAT, deposit, milestones, final payment and quotation expiry. Avoid a large unexplained upfront payment. Ask what happens if concealed defects, gas-supply limitations or extra work are found and insist that changes are authorised in writing before they proceed.
Our boiler quote checklist compares two or three written proposals on the same 100-point paperwork framework. It does not inspect the property, verify workmanship or recommend an installer; it helps you find unanswered questions before accepting a contract.
Common questions
Questions this guide should answer
What should be included in a boiler quote?
A useful written quote identifies the contractor and exact equipment, sets out controls and heating-system work, covers flue, condensate and utility changes, states removal and making-good boundaries, and records the total price, payment terms, compliance documents, warranties and exclusions.
How many boiler quotes should I get?
At least three written quotes is a useful consumer benchmark where practical. Give each installer the same brief so differences are caused by their proposal rather than missing information.
How do I check a boiler installer?
Search the business on the official Gas Safe Register and check the attending engineer's ID card and relevant work categories when they arrive. Also check the legal business named on the quote, insurance, reviews, payment terms and warranty support.
Is a boiler estimate the same as a quotation?
No. An estimate is an informed indication of likely cost. A quotation is an offer to do the stated work for the stated price, subject to any written conditions or variation terms.
Sources and review trail
We favour primary public guidance and link to the exact source so you can inspect it yourself.