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Is a combi boiler worth the extra installation cost?

VonLuck

I currently have a standard system boiler which is about 15 years old. It regularly loses pressure and I figure that it is due for replacement. I thought that replacing it with a combi boiler would be the best option as I have a small home and don't like the idea of heating up a whole tank of water just for one shower and the rest of the hot water goes to waste.

I recently got a quote to upgrade to a combi boiler. It's estimated at around €7k all-in. I didn't realise it would be this high, but the larger costs are due to the additional pipework required to make this system work, as well as a new combi pump due to the expected lower water pressure with this system. This is not to mention painting and plastering which is not included in the cost. Some of the pipework may require a box out in my living room (as there is no service zone to run in) which is not ideal either.

The alternative is just to replace my current boiler which would cost me €3k.

I suppose the question I'm asking is whether there is a significant (€4k+ over the lifetime of the boiler) financial benefit to a combi boiler over a system boiler? My gas bill for 2023 was around €1k so if I had this new boiler for another 15 years, I would need to save at least €275 on my bill each year to make financial sense.

The other alternative is to just keep getting my current boiler serviced and not replace it until it fails entirely!

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phormium

So if you seldom turn on the radiators what heats the apartment? Are you paying 1k per annum just to heat water or what else does the gas do for that money. It just seems a lot if not using radiators.

BTW I have a 32yr old gas boiler so just interested in what happens when I have to replace it!

VonLuck

https://www.boards.ie/discussion/comment/121566050#Comment_121566050

Thanks for all the suggestions. Very useful.

I highly doubt there is a leak elsewhere in the system. I live in an apartment so if there was water leaking I would definitely hear about it from my downstairs neighbour!

Very difficult to gauge whether the immersion method of heating the water would be cheaper. How would you even calculate that when there are so many variables?

I did consider air-to-air, but I'm not sure how practical that is in an apartment. Might need to have an unsightly unit on my balcony, assuming it's actually permitted by the management company.

antoinolachtnai

I think there must be a leak somewhere. If it was in the boiler then the service person would probably have seen it. Someone else might have a better proposal on what to do to find the leak.

If you used the top (sink) immersion with a proper timer on a smart meter deal with cheap night time electricity it would heat a smaller quantity of water to the temperature you desire. Because the element is near the top, and only the water above the element heats, it will heat a smaller quantity than the central heating coil, which is at a lower position in the cylinder. Electricitymight even then work out cheaper, especially in summertime when there is no benefit whatsoever from the lost heat. There are very cheap night time tariffs out there but they may not suit you because your overall consumption may turn out to be pretty low.

I think that it may in the future make sense to replace the gas system with an air-to-air heat pump system (not air-to-water). This would be an all-electric setup. This is not a mainstream thing to do at the moment but it may be more common in the future. That’s why I would be inclined to defer replacing your boiler to see how the market goes.

VonLuck

https://www.boards.ie/discussion/comment/121562728#Comment_121562728

The last time I got it serviced the guy said it was still fine, although on occasion I have got a hint of the smell of gas. The guy servicing said it was fine though. I thought that it might be on the way out when the pressure constantly drops. I have to top it up every 1-2 weeks on average.

https://www.boards.ie/discussion/comment/121562767#Comment_121562767

The only problem with this is that the water doesn't get properly hot in 30 minutes. A shower wouldn't be uncomfortable, but not at the ideal temp.

https://www.boards.ie/discussion/comment/121562847#Comment_121562847

Yes, shiny green stuff! I think it was built circa 2005-2007.

There is an immersion for the cylinder, but I have not once used it as I figure it is a huge expense.

BER rating is B2. Never need to put the rads on in the hallway or kitchen/living room as it's well insulated from surrounding apartments. Bedrooms are a different story and they can get quite chilly.

As per above, the boiler needs to be repressurised every 1-2 weeks on average in order to maintain a decent temperature of tap/shower water.

antoinolachtnai

https://www.boards.ie/discussion/comment/121562299#Comment_121562299

So it is a modern well insulated (shiny green stuff) cylinder? Can you give us an idea when the apartment was built?

Is there an immersion on the cylinder to heat by electricity?

do you know the BER rating for the home?

How often does the heating need to be repressurised?

on the whole it sounds like you can safely be minimise your investment in all things related to gas boilers. It would be different if you had a big draughty house or a family as you can imagine.

[Deleted User]

Heating the hot water cylinder from scratch takes about an hour using gas or oil. Putting it on for 20 or 30 minutes might be enough for you

Kaisr Sose

Agree with the economics...and there will be ongoing costs to heat water in the boiler so not saving the full €1.50 on heating full cylinder.

Have you been told the boiler is on last legs? You say it's 15yrs old but you don't use it much for heating a well insulated apartment so it should still have a lot of life in it.

VonLuck

https://www.boards.ie/discussion/comment/121562542#Comment_121562542

Good to know. Is there any way to artificially reduce the size of the hot water tank without replacing it? Say by inserting an inflatable bladder? My thinking is that I'd only need small volumes of water at a time, primarily for showers, and it would be more efficient just to heat the volume I need.

Also, how would I figure out what's causing the pressure drop? That sounds like the first port of call!

[Deleted User]

Heating tank of water is around €1.50 per day. You will be a long, long time trying to recover the extra for the combi at that rate.

As stated above replacing the boiling might not resolve the pressure drop issue unless it's part of the overall job

noodler

When I moved into my house a few years ago, I replaced the boiler with a combo.

It was old but it was also in the spare room (along with the hot tank).

So I moved it to the hall and also removed the hot tank.

About 5.5k in total (2021).

He did install a pump for the hot water downstairs and the hot/cold tap upstairs (and toilet).

It is very nosey and spits the water out at a pressure I don't like so I leave it off a lot. I was never entirely sure why it was needed - the low water pressure in the taps was sufficient for me. (I've an electric shower sadly so I get no benefit from the pump there).

VonLuck

https://www.boards.ie/discussion/comment/121561568#Comment_121561568

When you say the system, do you mean solely the plumbing aspects? I've queried it multiple times when I get my boiler serviced but they don't give me any clear answer. There is the suggestion that there's a leak somewhere, but there's no evidence of that at all.

I'm not sure what you're looking for when you ask what my hot water cylinder is like? In terms of condition I assume it is fine as I've never had an issue with it with leaks. Just had to replace the stopcock a few years back.

I am in a well insulated apartment so I don't really get the benefit of the hot water cylinder heating my home. I barely turn on the radiators year round.

By the sounds of it you wouldn't recommend a combi boiler in my situation?

antoinolachtnai

The loss of pressure is most likely to do with the system, not the boiler. Replacing the boiler won’t necessarily fix it.

what is your hot water cylinder like?

The heat from unused hot water doesn’t really go to waste in the winter months. The heat contributes to the warmth of your home, assuming it is indoors. During the summer is a different story, but the overall point is that the loss is probably less than you think.

You could look at other things to save energy. Draft proofing, insulation, etc. it may be worth saving towards some larger item rather than doing this upgrade.

Eventually you will need a new boiler but there might be a few years in it yet and if you have cash it might be better spent elsewhere.