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Boiler stove radiators

Updated: 22 October 2026

You want the stove to heat radiators, or a cylinder, and the first question is how many radiators a boiler stove will run. A reviewer's house is not a rating. The number you can take to an installer is the manufacturer's output to water, in kilowatts, after you have checked that the listing does not contradict itself. The six amazon.co.uk listings, captured on 19 October 2026, are on the [boiler stove comparison](/hub/fireplaces-and-stoves/boiler-stove). Notification and the ban on lighting a wet stove dry are on [boiler stove installation](/hub/fireplaces-and-stoves/boiler-stove/sub/boiler-stove-installation). A qualifying purchase can earn us a commission at no extra cost to you.

You want the stove to heat radiators, or a cylinder, and the first question is how many radiators a boiler stove will run. A reviewer's house is not a rating.

Our top picks

Prity Prity K1 CP W8 water-jacket stove

Best overall

Prity Prity K1 CP W8 water-jacket stove
4.5/10about £560
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Prity Prity FGW15 cooker, 5 kW and 15 kW

Rank 2

Prity Prity FGW15 cooker, 5 kW and 15 kW
7.4/10about £888.02
View offer
Prity Prity S3 W17 back-boiler stove

Best value

Prity Prity S3 W17 back-boiler stove
5.2/10about £801.53
View offer
On this page
  1. 1.Start from kilowatts to water
  2. 2.A reviewer's count is not a rating
  3. 3.Rules of thumb, labelled as such
  4. 4.Joining what you already have

Start from kilowatts to water

Output to water is what you compare with radiators and a cylinder. Output to the room stays around the stove. The Prity FGW15, at £888.02, states 15 kW to water and 5 kW to the room, with a 15 litre boiler and 1 inch connections. The 15 kW is the brief. The 5 kW is not spare radiator capacity. The Prity S3 W17 bullet, at £801.53, says 17 kW to the water jacket and 5 kW to the room, with a 23 litre jacket. The heat-output field says 5 kilowatts. You do not average 17 and 5. Until the data plate matches the bullet, that listing does not have a single water kilowatt. The K1 CP W8, at £560.00, claims a water jacket and states no kilowatts.

A reviewer's count is not a rating

A reviewer's count is a story about their pipework. Marc Fowler, in a UK review of the Prity FGW15, writes that he can see it powering four to six radiators, and that it needs fuel about every 30 to 40 minutes. A German reviewer says the system could take up to 15 radiators, then says they had only one and kept the fire low until more were added. A French reviewer describes eight radiators. None of those sentences is the 15 kW rating.
Prity Prity K1 CP W8 water-jacket stove

Testsieger

Prity Prity K1 CP W8 water-jacket stove
4.5/10about £560
View offer

Rules of thumb, labelled as such

Arada's choosing guide offers a sketch while you wait for the engineer. As that maker's guide, not as a statute: about 1 kW for each square metre of single-panel radiator, about 3 kW for a 120 litre cylinder, and about 10% extra for pipe losses. A heating engineer is supposed to confirm it. A large double panel is not a short single panel in a cloakroom. The heat leak sits inside that sum. Arada's BK555 and Stovax's Stockton call for a load that cannot be shut off, often about 10% of rated output, so heat has a path if the pump stops. If you valve that leak shut, you have removed the safety load. Fifteen kilowatts to water, on that single-panel guide, is on the order of 15 m² of panel before a cylinder and pipe loss. That sketch is not 15 radiators.

Joining what you already have

The default in those manuals is an open vent: a cold feed you cannot valve off, and a heat leak. A combi or other sealed system needs a designed link. The Solid Fuel Association points to a thermal store when a solid-fuel stove meets a sealed system. An unvented cylinder needs two tiers of safety under Part G. Central heating on a listing is not permission to tee into the combi. The Prity FGW15 is the listing you can start from, because 15 kW to water and 1 inch connections are on the page. The S3 W17 can enter only after the 17 kW bullet and the 5 kW field are reconciled. The K1 CP W8 cannot be sized from the Amazon page.

Common questions

How many radiators will 15 kW to water run?
There is no fixed count. The Prity FGW15 states 15 kW to water. Arada's guide, as a rule of thumb, uses about 1 kW per square metre of single-panel radiator, plus about 3 kW for a 120 litre cylinder and about 10% for pipes, and it says an engineer should confirm it. A UK reviewer guessed at four to six radiators. A German reviewer mentioned up to 15. Both are houses, not the rating.
Does the heat-leak radiator count in that number?
Yes. The heat leak is part of the load the water kilowatts have to serve, and it has to stay open when other radiators are shut. Maker manuals often describe it at about 10% of rated output. If you use the whole 15 kW for rooms you can valve off, you have not left the path those manuals ask for.
Can I connect the stove to a combi?
Only if the stove manual and a designed link say so. A combi is a sealed appliance. The wet-stove manuals cited here default to an open vent. A thermal store is how solid-fuel link-up notes describe joining a stove to a sealed system. Central heating on an Amazon title is not permission to tee into the combi.
Which listing in this set can I size from?
The Prity FGW15, because it states 15 kW to water and 5 kW to the room in words. The S3 W17 bullet states 17 kW to water, and you can size from it only after the conflicting 5 kW field is resolved on the plate. The K1 CP W8 does not give a labelled water kilowatt you can trust on the captured page.
What if the Amazon field says 5 kW and the bullet says 17 kW?
Do not choose the convenient figure. The Prity S3 W17 bullet says 17 kW to water and 5 kW to the room, and the heat-output field says 5 kilowatts. Ask for the plate or the manual. If they still disagree, do not order the stove as a 17 kW radiator boiler.

Related pages

Boiler stove buying guide

Best boiler stove

Boiler stove

Boiler stove installation: notify before you light

Boiler stove vs wood burner: when the water is needed

Sources

Public UK sources used for this comparison. amazon.co.uk prices, stars and review counts were taken from the listings on 19 October 2026.

  1. GOV.UK, Smoke control areas: the rules (retrieved 19 October 2026)
  2. Approved Document J (retrieved 19 October 2026)
  3. HETAS consumer FAQs (retrieved 19 October 2026)
  4. HSE, solid fuel back boiler alert (retrieved 19 October 2026)
  5. Regulation (EU) 2015/1185 Annex II (retrieved 19 October 2026)
  6. Defra Burn Better (retrieved 19 October 2026)
  7. Arada, choosing a boiler stove (retrieved 19 October 2026)
  8. Defra, cooker with boiler exempt list (retrieved 19 October 2026)