Do I have to replace the boiler before I sell the house?

Somebody is about to put a house on the market with a boiler that is old but working, and an estate agent or a relative has suggested replacing it first. It is an expensive suggestion and it is usually the wrong one.

The short answer is no. There is no legal requirement to replace a working boiler before a sale, no minimum standard it has to meet, and in most cases you will not get the money back in the price. There is one piece of preparation genuinely worth doing, and it is paperwork rather than plumbing.

What the law actually asks of you

Two things get confused here, so it is worth separating them.

The annual gas safety check is a landlord duty. HSE define a landlord for these purposes as somebody letting a property under a lease shorter than seven years or under a licence. Selling your own home is not letting it, so the duty does not apply to you and there is no gas safety certificate you are required to produce for a buyer. If you have one, fine. Its absence is not a problem you need to fix.

The Energy Performance Certificate is the requirement that does apply. You must have commissioned an EPC before the property is marketed, the rating has to be shown in the advertising, and the certificate must be given to the buyer. An EPC lasts ten years and is not invalidated by the sale, so if the house has had one in the last decade you may already be covered.

What there is not, for a sale, is a minimum rating you have to reach. The minimum energy efficiency standard that people half remember is a private rented sector rule for landlords letting property, not a condition of selling one.

Source: HSE, landlords' responsibility for gas safety; GOV.UK, selling a home: Energy Performance Certificates

What the buyer's survey will and will not do

A homebuyer's surveyor is not a gas engineer and will not test the boiler. What they will do is note its apparent age and condition and recommend a specialist inspection, which is a standard line rather than a verdict on your appliance.

That recommendation is what buyers negotiate with, and it is worth understanding what they are actually holding. They have a note saying the boiler is old and untested. If you have a service record, that note is answered. If you have nothing, the buyer is free to imagine the worst, and the number they ask you to knock off will be a guess made in their favour rather than yours.

So the leverage is not a new boiler. It is evidence about the old one.

The thing actually worth doing

Find the paperwork, and if the boiler is still young enough to be in guarantee, make sure the record supports it.

Manufacturer guarantees stay with the appliance in the property rather than travelling with you, and they survive a sale, but they survive it conditionally. Vaillant's own terms require the boiler to be serviced annually by a Gas Safe registered engineer, require those service details to be recorded in the Benchmark logbook, and require that logbook to be available for inspection during a visit. Their terms also state that moving the boiler to another property without their written consent invalidates the guarantee, which is the clearest possible statement that the cover belongs to the house.

Worcester Bosch approach the same point from the other side. Their terms say only the owner of the product can make a claim, and separately that rights under the terms may only be transferred to another person with their prior written consent, which they say will not be unreasonably withheld. In practice that means a buyer inheriting a boiler in guarantee should contact the manufacturer to get the record put in their name, and it means the service history has to exist for any of it to be worth anything.

So the job before marketing is: locate the Benchmark logbook, locate the service records, locate the Building Regulations compliance certificate if the boiler was fitted in the last few years, and put them together. A boiler in guarantee with a complete history is a selling point. The same boiler with no paperwork is treated as an unknown.

Source: Vaillant, domestic boiler guarantee terms and conditions; Worcester Bosch, guarantee terms and conditions

When replacing first is the right call

It is not never. There are three situations where doing it before the sale genuinely makes sense.

The boiler is not working, or an engineer has classified it as unsafe. A house that cannot be heated is a different proposition to a house with an old boiler, and buyers price that gap far above what the work costs.

The sale has already fallen through once on the heating. At that point the question is no longer whether it is worth it in theory.

Or you were going to replace it anyway within a year or two. Doing it while you still choose the timing, the model and the installer is much better than the buyer's solicitor doing it for you in a retention negotiation.

Outside those, the money usually goes further as a small reduction in the asking price than as a new appliance the buyer did not choose.

• Boiler not working or classified unsafe: replace, or expect the sale to carry it
• A previous buyer already walked over it: replace
• You were replacing it within a year or two regardless: replace now, on your terms
• Old but working, with a service history: leave it and hand over the paperwork

If a buyer asks you to knock money off

Ask what for. A note in a survey saying the appliance is old and was not tested is not a fault, and it is not a costed item. If the buyer wants a figure, the reasonable answer is that they are welcome to get a Gas Safe registered engineer to inspect it, which is what the survey suggested in the first place.

If that inspection finds something real, then it is a real negotiation and you have a choice: fix it, discount it, or leave it. If it finds nothing, the point has gone away and it cost you nothing to prove.

Where you do decide to replace, do it as a planned job rather than under offer with a deadline. A boiler bought in a hurry is bought badly, and the whole reason a working boiler is worth keeping is that it leaves you the time to compare.