Comparing Boiler Quotes: What Each One Should Include

To compare boiler quotes properly, first make sure every quote is for the same job: the same boiler output, the same scope of work (flue, gas pipe, condensate, system clean, filter and controls), the same warranty length and conditions, and the same paperwork at the end. Only once those line up does the price at the bottom tell you anything. Most of the gap between a cheap quote and an expensive one is in that list, not in the installer's margin.

Why quotes for the same house differ so much

A new boiler is not a product with one price. It is a product plus a variable amount of work around it, and every installer makes their own call about how much of that work your home needs. One quote might assume the boiler goes back in the same spot with the same flue, while another allows for moving the flue to meet current rules. One includes upgrading an undersized gas pipe, another says nothing about it and finds out on the day. One fits a mid-range boiler with a long warranty, another a budget model with the minimum. All three are "a new combi boiler", and they are three different purchases.

A quote should follow a survey

A fixed price given over the phone or from a web form, before anyone has looked at the property, is an estimate with conditions attached, whatever it calls itself. The things that move the price (flue route, gas pipe size, condensate route, the state of the existing system, access) can only be confirmed in person. A proper quote comes after a survey and is fixed in writing. If one of your quotes came without a survey, treat it as provisional and ask what could change it. Our guide to choosing a boiler installer covers the other checks worth making before you sign.

The line items to check on every quote

• Boiler make, model and output. The exact model, not "a Worcester" or "an A-rated combi". Output in kW should come from the survey, not a guess, and if quotes disagree on size by a wide margin, ask each installer to explain their figure. Our guides to Vaillant model numbers and the Worcester Bosch Greenstar range show what those names and numbers mean.
• Boiler position and flue. Same position or moved? Horizontal or vertical flue? Is a flue extension or plume kit included where needed?
• Gas supply pipe. Modern boilers, combis especially, often need a larger gas pipe than the old boiler had. Is an upgrade included, or excluded pending inspection?
• Condensate pipe. Where it drains, and whether an external run is insulated or sized to resist freezing.
• System clean and filter. Chemical flush or power flush, and a magnetic filter. Manufacturers usually expect the system to be cleaned and protected for the warranty to hold.
• Controls. Which thermostat or programmer is included. In England, a combi replacement has to meet the Boiler Plus rules on controls.
• Removal and disposal. Taking away the old boiler, and any cylinder and tanks if the system type is changing. See old boiler removal and disposal.
• Commissioning and paperwork. A completed Benchmark checklist and Building Regulations notification through the Gas Safe scheme should both be standard.
• Warranty. Length, who registers it, and what you have to do to keep it (usually an annual service).
• Timing and payment. How many days, and what is payable when.

Put them side by side

The quickest way to spot the real differences is a simple table with one column per quote. Anything a quote leaves blank is a question to ask, not a saving.

Reading the warranty line properly

Headline warranty years are one of the easiest things to compare badly. The longest warranties are usually only available when the boiler is fitted by an installer accredited with that manufacturer, and they come with conditions: registration within a set period, a filter fitted, and an annual service by a Gas Safe engineer. A ten-year warranty you will not keep up the conditions for is worth less than it looks. Ask each installer which manufacturer schemes they hold and who registers the warranty. The Benchmark checklist article explains why that piece of paper matters to your cover.

Where cheap quotes find their savings

A cheap boiler and installation is not automatically a bad one. Some homes genuinely need a simple like-for-like swap, and that should cost less. But when one quote is far below the others for the same house, the saving usually comes from somewhere specific:

• A budget boiler range with the shortest warranty.
• No system clean or filter, so a new boiler goes onto dirty system water.
• Gas pipe, flue or condensate work left out and priced as extras on the day.
• The most basic controls that just about meet the rules.
• Removal, disposal or making good not included.

None of those are wrong in themselves if they are stated plainly. The problem is when they are not stated at all. The full list of cost drivers is in what affects the cost of a new boiler installation.

Red flags worth walking away from

• Pressure to sign on the day, or a discount that expires tonight.
• A discount for paying cash with no written quote or paperwork.
• No Gas Safe registration number on the quote, or reluctance to give one.
• A recommendation to go much bigger "to be safe" with no heat loss reasoning behind it. See what to do if an installer recommends a bigger boiler.
• Vague scope: "supply and fit new boiler" and a number, nothing else.

Getting a quote you can compare

Every quote we give follows a free survey, names the boiler and its output, lists what is and is not included, and is fixed in writing, so it can sit in that table next to anyone else's. If you already have quotes and want a third to compare against, book a free survey or read how our new boiler installation process works first. Spreading the cost is covered in boiler finance options.