A back boiler stove, plumbed into your heating, costs €3,500 – €5,500 fitted and takes two to three days. It heats the room it sits in and sends the rest of its heat to the hot water cylinder and the radiators. It is worth the money when the house is on oil, the fire is lit most evenings, and the hot press is close to the stove. In Johnny's experience, under 7 metres works best for that last one.
The distance to the hot press is the part people don't expect, so a good part of this page is about it.
At a glance
- Fitted price: €3,500 – €5,500, liner extra if the chimney needs one.
- Time on site: two to three days.
- Radiators: about 12 from a good one.
- Hot press: under 7 metres from the stove works best.
What a back boiler stove does
A back boiler stove is a stove with a water jacket built around the firebox. The fire heats the room through the glass and the casing like any stove. The water jacket carries the rest away through two pipes to the cylinder in the hot press, and from there a pump sends it around the radiators.
The output is split, and the split is printed on the stove's data plate. Waterford Stanley list their Fern Eco boiler stove at 3.6 kW to the room and 7.2 kW to the boiler at nominal output, with a maximum of 5 kW and 10.5 kW. Two thirds of the heat goes to the water.
That matters when you are choosing one. For example, a stove sold as 13 kW might put only 4 kW into the sitting room and 9 kW into the water. Size it on the big number and you get a room nobody can sit in, or a stove that is run shut down all evening, which tars the flue. Our stove size calculator works off the room figure.
What a back boiler stove costs fitted
| Work | Typical range | Time on site |
|---|---|---|
| Home survey, camera down the flue where needed | Free, no obligation | About an hour |
| Boiler stove, plumbed into your heating | €3,500 – €5,500 | 2 – 3 days |
| Chimney liner, if the survey calls for one | €1,000 – €2,500 | Same visit |
| Twin-wall flue, where there is no chimney | €1,800 – €3,200 | 2 – 4 days |
Prices include VAT and are a guide. The exact figure comes after the survey, in writing, before any work starts.
The stove is the smaller part of the spread. The plumbing is the bigger part: how far the pipes run to the hot press, whether there is an old back boiler and pipework to reuse, and what cylinder and controls are there already. That is why the survey includes a look in the hot press as well as up the chimney.
It is also why the job takes two to three days where a room-only stove takes one day. For comparison, a room-only inset stove is €2,200 – €3,500 fitted and a freestanding one is €2,500 – €4,000. The full breakdown is on the stove installation cost page. There is no SEAI grant for a stove of any kind, so the price you are quoted is the price.
How many radiators will a boiler stove heat?
Johnny's rule of thumb is that a good boiler stove heats about 12 radiators nicely.
A recent job went past that number. The house had 16 radiators and the stove fitted was a Stanley Fern. The house was zoned, so the stove heats downstairs first, and there is the option to send hot water to the upstairs radiators.
Radiator count is only a guide. A long double radiator gives out far more heat than a small single, and takes that much more from the stove. What settles it is the stove's output to water against the heat your radiators and cylinder need, and that gets worked out at the survey.
The run to the hot press: under 7 metres works best
If you are fitting a back boiler stove from scratch, the distance from the stove to the hot press comes first. Johnny puts it plainly: if that run is too long, it won't work, and under 7 metres works best.
The gravity circuit is the pair of pipes between the stove and the cylinder that moves heat with no pump. A solid fuel fire can't be switched off the way an oil burner can, so those pipes have to work on their own. Hot water rises to the cylinder and cooler water falls back. That only works over a short run in wide pipe.
Stanley's installation manual for the Fern solid fuel boiler stove puts numbers on it: 28 mm flow and return pipes, no more than 7.8 metres of pipe, lagged, with no gate valves on the circuit. It adds that the shorter the run, the more effective the water heating. That is a pipe length, so the bends count, and Johnny's 7 metres sits inside it.
If there is already a back boiler behind the open fire, the pipework to the cylinder is in place. In Johnny's words, there is no problem. A long bungalow with the sitting room at one end and the hot press at the other is a different job to a two-storey house with the hot press over the fire. It is better to hear that at the survey than after the stove is bought.
The parts of the job you can't leave out
Stove makers set out the plumbing in their manuals. Stanley's, for the Fern, requires a gravity circuit with an expansion pipe open to the atmosphere, so if the water overheats it has a way out. The heat leak radiator is one radiator left with no valve that can shut it. It means the stove always has somewhere to send heat if the pump stops or the power goes, and it is what stops the system boiling.
The room needs a permanent air vent. For a stove that takes its air from the room, Technical Guidance Document J asks in Table 1 for a ventilation opening of 550 mm² per kW of rated output and never less than 6,500 mm². That is the figure for most houses built before 2008. In an airtight house it is higher: 6,500 mm² plus 550 mm² for every kW above 5. There is no exemption for small stoves in Ireland, whatever a UK website tells you.
The house needs carbon monoxide alarms. Where a new or replacement stove is fitted, TGD J, section 1.5.2, asks for one in the room with the stove and one either inside each bedroom or within 5 metres of the bedroom door, measured along the corridor.
And the chimney has to suit. The Fern Eco has a 150 mm flue outlet, and whether your chimney needs a liner is decided by a camera. The chimney checker gives you a first idea before anyone calls out.
Is a stove with a back boiler worth it?
It is worth it in a house that heats on oil, where every evening the stove is lit is an evening the burner is not. The fire needs to be lit most evenings from October to March, because the radiators only get heat while it is burning. It helps a lot if you can buy timber in bulk and keep it dry. SEAI's Domestic Fuel Cost Comparison prices timber by how it is bought, and how you buy it changes the cost of the heat more than the stove does. The figures are set out in our stove guide.
It is not worth it if the hot press is a long way from the stove. It is a poor fit for a house that is empty all day, where you want heat on a timer, because a fire can't give you that. And watch the size of the room: even a modest one like the Fern Eco puts 3.6 to 5 kW into the room it stands in.
The honest alternative. A room-only stove at €2,200 – €3,500 fitted, with the heating system left alone. It is one day's work, not two or three, and it suits most houses where the stove is for the sitting room in the evening. The guide to choosing a stove covers the choice.
Inset or freestanding back boiler stove?
Both are made. An inset model sits into the fireplace opening. A freestanding one stands out on the hearth: the Fern Eco is 600 mm wide, 600 mm deep and 710 mm high, with a flue outlet on the top and the rear. Which one fits is usually settled by the opening you already have. The stove selector takes about a minute and narrows it down.
If you can't tell whether a back boiler stove suits your house, the survey is free. Know where your hot press is before you ring.
Back boiler stove questions
How much does it cost to put in a back boiler stove?
A boiler stove plumbed into your heating costs €3,500 to €5,500 fitted with us, and takes two to three days. If the survey finds the chimney needs a liner, that is €1,000 to €2,500 on top. The survey is free and the exact price is given in writing before any work starts.
How many radiators can a back boiler stove heat?
Johnny's rule of thumb is that a good boiler stove heats about 12 radiators nicely. On a recent job with 16 radiators and a Stanley Fern, the house was zoned, so the stove heats downstairs first and there is the option to send hot water to the upstairs radiators.
Is a stove with a back boiler worth it?
It is worth it when the house heats on oil, the fire is lit most evenings in winter, and the hot press is close to the stove. It is a poor fit when the hot press is a long way off, when nobody is home to light and feed the fire, or when you only want to heat one room. A room-only stove is €2,200 to €4,000 fitted.
Can you replace an old back boiler with a boiler stove?
Yes. If there is already a back boiler behind the fire, the pipes to the cylinder are in place, and in Johnny's words there is no problem. The survey still checks the pipework, the cylinder and the controls before a price is given.
How far can a boiler stove be from the hot water cylinder?
Under 7 metres works best, in Johnny's experience. Waterford Stanley's installation manual for the Fern solid fuel boiler stove sets a limit of 7.8 metres of pipe between the stove and the cylinder, and says the shorter the run, the more effective the water heating.
Is there a grant for a back boiler stove in Ireland?
No. There is no SEAI grant for installing a stove of any kind, boiler stoves included.
What size boiler stove do I need?
Size it on two figures. The output to the room has to suit the room the stove sits in, and the output to water has to suit the radiators and cylinder. Stanley list the Fern Eco at 3.6 kW to the room and 7.2 kW to the boiler at nominal output.
Find out if one suits your house
Johnny surveys it for free: the chimney, the hot press and the run between them. You get a price in writing before any work starts. Leinster and Waterford.
Related reading
Sources: Johnny Roberts, October 2026 (radiator numbers, the 7 metre run, the 16-radiator job). Waterford Stanley, Fern Eco boiler stove (outputs and dimensions). Waterford Stanley, Fern solid fuel boiler stove installation and operating instructions (gravity circuit, heat leak radiator). Technical Guidance Document J, 2014 (air supply, carbon monoxide alarms). SEAI Domestic Fuel Cost Comparison.