Boiler Installation

Combi, system or heat-only: which boiler does your home need?

A combi boiler suits most homes with one or two bathrooms and decent mains pressure: it heats water on demand with no cylinder or tanks. A system boiler with a cylinder suits larger homes where two or more showers run at once. Heat-only (regular) boilers suit older gravity-fed systems you do not want to re-engineer.

The deciding factors are hot water demand and mains supply, and we measure both — a combi is only as good as the cold main feeding it. The large detached homes we work on in Esher, Cobham and Oxshott almost always justify a system boiler and an unvented cylinder, because three bathrooms drawing at once will defeat any combi. A 1930s semi in Molesey or Walton with one bathroom is classic combi territory. Heat-only boilers still earn their place in the Victorian and Edwardian houses around Surbiton, Kingston and Thames Ditton, where original gravity systems sometimes make a like-for-like swap the most economical option — a judgement call about pipework condition we will make honestly rather than defaulting to the biggest job.

What does a new boiler cost in Surrey in 2026?

A like-for-like combi swap typically costs £2,200–£3,500 fully installed in 2026, depending on the boiler model, flue arrangement and pipework alterations. Converting from a system or heat-only boiler to a combi runs £3,500–£5,500 because of the extra pipework, cylinder removal and gas supply upgrades usually involved.

Where a quote lands inside those ranges comes down to specifics we can only confirm by looking: whether the gas supply pipe needs upsizing for a modern combi, where the flue can exit, and the condensate route. A magnetic filter — £125–£180 fitted if quoted separately — is included in our installations as standard, partly because several manufacturers extend their guarantee when one is fitted.

Be wary of a price given over the phone to the pound, and equally wary of a monthly figure with no total attached: our quotes are itemised and fixed, and if we find something unforeseeable mid-job we stop and talk to you before any extra cost exists.

Which boiler brands do we install?

We install and are trained on the leading brands: Worcester Bosch, Vaillant and Ideal make up most of what we fit, with Baxi and Viessmann where the budget or the specification points that way — recommended from what suits your home and water conditions.

The honest picture in 2026 is that the big manufacturers all build good boilers; the differences show up in guarantee length, parts availability and how the heat exchanger copes with hard water. Worcester Bosch and Vaillant command a premium and carry the longest guarantees — up to 10–12 years depending on the model and whether a magnetic filter is fitted. Ideal and Baxi deliver strong value with guarantees typically in the 7–10 year range, and Viessmann's stainless steel heat exchangers are a genuinely good match for Surrey's aggressive water.

What we will not do is invent credentials: our site will carry manufacturer accreditations only once they are confirmed and current, and the guarantee lengths we quote are the manufacturers' own published terms for the boiler and filter combination on your quote.

How long does a boiler installation take?

A straight like-for-like combi swap takes one day: old boiler out in the morning, new one commissioned and heating the house by late afternoon. A system-to-combi conversion takes two days, and a full conversion with relocated boiler or significant pipework typically two to three days.

The sequence on a standard swap is predictable. We drain the system, strip the old boiler and flue, make good the gas and water connections, hang the new boiler, fit the new flue and condensate run, add the magnetic filter, cleanse the system to BS 7593, dose it with inhibitor, then commission and demonstrate the controls. You are without heating and hot water only during working hours. Conversions take longer because of what the swap drags with it — decommissioning a cylinder and loft tanks, new hot water pipework, often an upsized gas supply — and we would rather quote two honest days than promise one and cut corners at nine in the evening.

How do boiler guarantees work — and how do you keep yours valid?

Manufacturer guarantees on the boilers we fit run up to 10–12 years depending on brand, model and whether a magnetic filter is fitted — but every one of them has the same two conditions: the boiler must be registered within 30 days of installation, and it must be serviced annually by a Gas Safe registered engineer.

We handle the first condition for you. The Benchmark commissioning checklist — the industry-standard record of how the boiler was installed and commissioned — is completed on the day, and we register the boiler with the manufacturer before we invoice, so the clock starts correctly and the full term applies. Plenty of guarantee claims fail simply because nobody did this paperwork.

The second condition is yours to keep, and it is the cheapest insurance in home ownership: one annual service, around £90–£110, with the date recorded in the Benchmark logbook. Miss a year and the manufacturer can reduce or refuse a claim — so we send service reminders to installation customers, and the guarantee you paid for is still standing in year nine when it matters most.