Boiler quotes: how to compare them properly
To compare boiler quotes properly, check that each one covers the same job: the same type and size of boiler, the same position, the same flue and condensate route, system cleaning, a filter, controls, Building Regulations notification and the warranty registration. Two quotes that look far apart on price are often quoting for different work, and the cheaper one may leave out things you will need anyway. A quote based on someone looking at your home is worth more than a figure produced from a few questions online, because the parts that change the price are usually the ones a form cannot see.
Loyal Plumbers · Updated
Discuss a boiler replacementOnline prices versus surveyed quotes
Online boiler quotes ask about your current boiler, the number of bedrooms and bathrooms, and where the flue comes out, then give a fixed figure. They are useful for a rough idea. The catch is that the figure rests on your answers being right and on the installation being straightforward, and the terms usually allow the price to change once an engineer arrives and finds something different.
A surveyed quote comes after someone has looked at the boiler position, the flue route, the gas supply, the condensate drain, the pipework and how you use hot water. It takes longer to arrive, but it is the one you can hold the installer to. If you are comparing an online price with a surveyed quote, ask the online company what would trigger a change on the day.
What a complete boiler quote should list
Ask each installer to break the quote down so you can see what is and is not included. A single total with the boiler model name tells you very little.
| Item | What to check |
|---|---|
| Boiler | Exact make, model and output, and why that output suits your home |
| Position | Same place or a move, and any pipework or making good that a move involves |
| Flue | New flue included, route, any extensions or plume kit, access needed outside |
| Condensate | Where it drains and whether an external run needs protecting from frost |
| Gas supply | Whether the existing gas pipe is adequate for the new boiler or needs upgrading |
| System cleaning | How the heating system will be cleaned and treated with inhibitor |
| Filter | Magnetic system filter included, and its make |
| Controls | Thermostat and programmer included, and how they meet current rules |
| Removal | Old boiler, and any redundant tanks or cylinder, taken away and pipes capped |
| Paperwork | Building Regulations notification, commissioning checklist and warranty registration |
The items that make the biggest difference
Moving the boiler, changing from a system with a cylinder to a combi, or the reverse, adds pipework, electrics and making good. So does a flue that cannot go straight out through the wall behind the boiler. If one quote assumes the boiler stays put and another plans to move it, you are not comparing the same job.
Gas supply size is another. A new boiler may need a larger gas pipe from the meter than the old one had. One installer may have checked and included it, another may not have looked. Ask directly whether the gas supply has been assessed for the proposed boiler.
System cleaning matters more than it looks. Sludge from the old system can damage a new boiler, and the Building Regulations compliance guidance expects the system to be cleaned and treated when a boiler is replaced. Manufacturers usually expect it too as a condition of their warranty. A quote that skips it is cheaper for a reason.
Boiler size and type: check the reasoning
A good quote explains why the proposed boiler suits your home rather than simply naming a bigger one. For a combi, the hot water output matters as much as the heating, because it decides how well a shower runs while someone else uses a tap. For homes with more than one bathroom used at the same time, a system boiler with a cylinder is often the better fit, and a quote that pushes a large combi without discussing that is worth questioning.
If quotes propose different types of boiler, that is not necessarily wrong, but each installer should be able to tell you why. Our guides to the types of boilers and to choosing between a combi and a system boiler cover the trade-offs.
Controls and the rules they must meet
In England, replacement gas boilers must meet minimum efficiency and control standards set out in the Building Regulations guidance. Every installation needs time and temperature control, and a combi installation needs an additional energy-saving measure such as weather compensation, load compensation, flue gas heat recovery or a smart thermostat with automation and optimisation.
Check that each quote names the controls it includes. A quote that leaves them out is either assuming your existing controls will do, which may not satisfy the rules, or will add them later.
Who is doing the work and what paperwork you get
Any work on a gas boiler must be carried out by a Gas Safe registered engineer. Ask for the engineer's name and check their Gas Safe ID card on the day: the back of the card lists the types of gas work they are qualified to do. You can check the registration number with the Gas Safe Register before the installation date.
After installation you should receive a completed commissioning checklist, the manufacturer's paperwork and confirmation that the installation has been notified under the Building Regulations, which leads to a compliance certificate being sent to you. Warranty length often depends on the installer registering the boiler with the manufacturer and on annual servicing. Ask who registers it and what servicing the warranty needs.
Quote, estimate and your right to cancel
Citizens Advice distinguishes a quote, which is a fixed price for agreed work, from an estimate, which is a best guess that can change. Ask each installer which they are giving you and what could change the figure. Get it in writing, with the payment stages set out.
If you agree the contract in your own home, for example at the end of a survey visit, you normally have a 14-day cooling-off period under consumer law. If you want work to start inside that period, the installer should ask you to request that in writing.
Ask us for a surveyed quote
Loyal Plumbers replaces and installs boilers across London and everywhere inside the M25, and the gas work is carried out by Gas Safe registered engineers. We survey before we quote, so the quote covers the flue, condensate, gas supply, system cleaning and controls your home actually needs, itemised so you can compare it line by line with anyone else's.
Call us or send an enquiry with your current boiler make and model, where it is, and how many bathrooms you have.
Common questions
- How many boiler quotes should I get?
- Two or three surveyed quotes are usually enough to compare. More than that rarely adds much, as long as each one lists the same items so you can compare them line by line.
- Why do boiler quotes vary so much?
- They often cover different work. A move, a new flue route, a gas pipe upgrade, system cleaning or new controls can be included in one quote and missing from another.
- Are online boiler quotes accurate?
- They can be for a simple swap in the same position. The price usually depends on your answers being right, and the terms normally allow changes if the engineer finds something different on the day.
- Should a boiler quote include a power flush?
- It should include some form of system cleaning and inhibitor. Whether that is a power flush or another cleaning method depends on the system's condition, and the installer should explain the choice.
- Do I need Building Regulations approval for a new boiler?
- The installation must be notified. A Gas Safe registered installer normally does this for you, and you then receive a Building Regulations compliance certificate.
Sources and further reading
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