How Much Does a New Boiler Cost in Kent in 2026? (Real Itemised Numbers)

By Lucas Morley, owner and heating engineer at Evo Flow Heating (Heat Geek partner, Gas Safe registered) · About Evo Flow Heating · Last updated 2026-06-15

I had a customer in Dartford last winter ring me to say she had three boiler quotes ranging from 2,650 pounds to 4,950 pounds. Same house. Same boiler model on two of the three. She wanted to know which one was the rip-off. The honest answer was none of them. They were just quoting three different jobs and calling them the same job.

That is the situation most Kent homeowners are in when they go out for new boiler quotes. The bottom-line numbers look like they are comparable. They are not. What I want to do here is walk you through what a properly itemised new boiler quote in Kent actually looks like in 2026, with real numbers for the three property types we see most: a Dartford semi, a Maidstone terrace and a period detached out toward Sevenoaks. So that when you have three quotes in front of you, you can tell which one is the rip-off and which one is the sensible buy.

What is actually in a new boiler quote (the line items that matter)

A properly itemised new boiler quote in Kent will have seven line items, broken out separately, not bundled into one number. The boiler itself, the flue and flue terminal, the controls, any pipework changes, the labour for the install day, the commissioning and balancing on the last day, and the VAT shown separately. Anything bundled into a single figure makes it harder to compare three quotes and easier for an installer to bury margin.

The boiler line is usually the smallest surprise. A mid-range Worcester, Vaillant, Viessmann or Ideal combi in 2026 retails to the installer somewhere between 950 and 1,800 pounds depending on the model and the output. The flue kit adds 150 to 350 depending on the run. The controls line is where most installers diverge from each other: a basic wired thermostat costs 50 to 80, a smart on-off thermostat (Nest, Hive, Tado) costs 180 to 280, and a proper modulating weather compensation control with an outdoor sensor costs 250 to 450 fitted. Those three are not interchangeable. The modulating one will run your boiler on a lower flow temperature for most of the heating season, which is where the real running cost saving lives.

Pipework changes are the variable. A like-for-like swap on a Dartford semi where the existing boiler is in the same location costs 200 to 400 pounds in pipework. A relocation (e.g. boiler moving from a bedroom cupboard to the kitchen) is 500 to 1,200 pounds depending on the route. A combi from system swap (where the old hot water cylinder is removed) is somewhere in between. Always ask whether the quote includes pipework changes and what those changes are. A like-for-like quote with no pipework changes on a 2026 installation is rarely a full picture.

Real 2026 itemised numbers for a typical Dartford semi

Take a typical three-bed semi in Dartford, replacing a tired 15-year-old combi with a new modern combi in the same location. The honest itemised total for a properly designed install lands in the 3,200 to 3,800 pound region. That breaks down roughly as: 1,300 boiler, 250 flue, 320 modulating controls, 250 pipework refresh (new isolators, magnetic filter, gas tightness check, system flush), 800 labour for two days, 250 commissioning, plus VAT shown separately.

If you have a quote in Dartford that is below 2,800 pounds for the same job, look carefully at the controls line and the commissioning line. The cheap quotes almost always swap the modulating control for a basic thermostat and skip the proper balancing pass. The kit on the wall looks the same, the install day is shorter, but the running cost over the next fifteen years tells the real story.

If you have a quote that is above 4,500 pounds for the same job, there should be a clear reason on the page. Either there is a pipework or boiler relocation in the quote, or there is a system rebuild (e.g. an old microbore system being replaced with proper 22mm flow and return), or the kit is a higher-tier boiler (Viessmann 200-W rather than 100-W, or equivalent). If none of those reasons appear on the quote, ask before you accept.

Real 2026 itemised numbers for a Maidstone terrace and a Sevenoaks period detached

A two-bed terrace in Maidstone with the boiler tucked into a kitchen cupboard, replacing a system boiler with a modern combi (so the old hot water tank is removed and the airing cupboard is freed up) lands in the 3,800 to 4,400 pound region. That includes the cylinder removal, the pipework reroute, the modulating controls and the balancing. The terrace stock around Maidstone is varied and the old cylinder removal sometimes uncovers ancient pipework that needs swapping out, which can push the number up another 200 to 400.

A four-bed period detached out toward Sevenoaks, replacing a regular boiler with a new regular boiler plus a new unvented cylinder, plus zoned modulating controls (upstairs and downstairs on separate weather compensation curves), lands in the 5,500 to 7,500 pound region. That sounds a lot until you see what is on the bill: a 250 litre stainless cylinder is 1,400 to 1,800 by itself, the zoned controls add 600 to 800 on top of a single-zone install, and the labour is three to four days rather than two.

What you should NOT see at any of these price points is a missing commissioning line. Commissioning, the balancing pass and the flow temperature setting, is what makes the difference between a system that costs you 1,400 pounds a year to run and a system that costs you 1,800 pounds a year to run, on the same boiler in the same house. That difference, over the life of the install, dwarfs the headline price.

Why the cheap quote is usually expensive and the dear quote is sometimes the cheap one

Most Kent homeowners ringing round for boiler quotes are sensible value-orientated buyers. They want the right kit at a fair price. The trouble is, the bottom-line totals on three quotes can be 1,500 pounds apart and the three quotes are not actually for the same job. The cheap quote will have a basic thermostat where the others have modulating controls. The cheap quote will skip the magnetic filter where the others include it. The cheap quote will fit a like-for-like flue where the others price for a relocation that the regs now require. The cheap quote will skip the balancing pass on the radiators and just leave the lockshields at whatever position the previous installer left them.

What that means in practice is: the cheap install runs hotter than it should, the boiler short cycles, the running cost is 15 to 25 percent higher than the proper install on the same boiler, and a couple of years in the system sludges up because nobody fitted the filter. The proper install costs 800 pounds more on day one and saves 200 to 400 pounds a year in running cost and a couple of weekend call-outs. Over fifteen years, the proper install is the cheap one.

If you would like a like-for-like itemised quote for your new boiler in Kent, that is what we do. Free survey, heat loss check, written itemised quote with every line broken out, and a commissioning pass that includes the balancing. We are Gravesend, Dartford, Maidstone and the wider Kent area. If your current boiler is more than twelve years old and you are also weighing up whether a heat pump makes more sense long-term, we will run that comparison for you on the same survey visit.

• Get three quotes in writing, each broken out by line item. If a quote arrives as one number, ask for the breakdown before you put it in the comparison.
• Compare the controls line, not the totals. A modulating weather compensation control is worth the price difference in the first heating season.
• Check the commissioning line is present. “Commissioning and balancing” or “system balance” is what stops the cheap quote being a false economy.
• Ask whether a magnetic filter is included, and whether the system is flushed before the new boiler goes on. Both should be standard, not extras.
• Check the warranty period: a Worcester, Vaillant, Viessmann or Ideal combi installed by an accredited installer should carry a 10 to 12 year warranty. Less than that, ask why.
• Confirm the engineer is Gas Safe registered and ask to see the card on the day. A reputable Kent heating engineer expects this and welcomes it.
• Do not pay a deposit upfront. Pay on completion or in staged payments tied to install milestones. A deposit before the work starts is not how a properly run heating business operates.

Frequently asked questions

For more Kent heating advice, browse the Evo Flow Heating blog or call Lucas on 01474 612061.