New boiler gas use

[Gaggsy]

Good news, my new boiler is being installed today and I was wondering how the better efficiency is going to affect my gas usage.
Would anyone know how to do a rough calculation, all things being equal? Obviously there will be other improvements as I now have a new HW cylinder, new controls and everything's been powerflushed.

Here are the details:
Old boiler: Potterton Kingfisher 2, CF100. Non-Condensing Conventional boiler with a maximum power output of 29.3kw. SAP seasonal efficiency rating of 65.0%. It's 30 to 35 years old so probably not been achieving that efficiency rating recently.

New boiler: Ideal Logic Max S30 30kW System Boiler with Filter 218871. ERP Efficiency 93%; SEDBUK SAP 2009 Rating 89.60%; SEDBUK SAP 2005 Rating 91.10%.

This is used to heat the 16 radiators. The only other gas appliance in the house is a gas hob. My gas use was 40,000 KWh per year.

What can I expect my new annual gas use to be?

Many thanks
Gaggsy?

[Gaggsy]

Sorry, got interrupted and hit send before final read-through.
The boiler heats the hot water and 16 radiators.

I'm definitely Gaggsy. Ignore the question mark!

[Howard]

Sorry, got interrupted and hit send before final read-through.
The boiler heats the hot water and 16 radiators.

I'm definitely Gaggsy. Ignore the question mark!

Sorry to post bad news. My 20 year old Potterton boiler was replaced with a new condensing boiler around three years ago. I monitor my gas usage with a spreadsheet and the savings were very small. I'd estimate it was between 10 and 20%. A cynical friend saved the money by not replacing his Potterton and despite a couple of modest repairs he has probably saved a few thousand pounds compared with me.

Where I did save money was in stopping my expensive British Gas service cover (which they increased because of the age of my previous boiler) and replacing this with cover from my new boiler installers. This is a saving of over £200 a year for a 5 bed house.

Hope you fare better!

regards

Howard

[tjh290633]

We changed our 1977 boiler for a new non-condensing model in 1998. The comparison of gas usage before and after the change shows a 40% saving.

We have never had a boiler maintenance contract, as from what friends tell me, they usually lead to trouble afterwards. My newer boiler has been attended to on 3 occasions. Once for failing to ignite - lighter spark position adjusted; once to replace a circuit board; once to replace 3-way valve. There is virtually nothing inside the boiler that need servicing.

TJH

[richlist]

Surely the secret to using less energy to heat a property is to increase its insulation before installing a new boiler ?

[Alaric]

There is virtually nothing inside the boiler that need servicing.

An annual inspection should make sense for gas safety reasons. If you can find a reliable local independent heating engineer/plumber to make annual visits, that's an alternative to the packaged and expensive British Gas etc plans.

[Howard]

Gaggsy

I've just looked at the spreadsheet which records our actual gas usage since the new condensing boiler was installed. It indicates that our usage hasn't changed much. In fact I'd guess that the weather each year makes more difference.

Your gas usage does look very high. We have a well-insulated house with 19 radiators and only use around 24 - 25,000 kWh of gas a year. Just two of us plus family staying occasionally, but we don't tend to be away for long periods so the house is always heated. I do turn radiators off in rooms which aren't used and almost all have thermostatic controls.

I'm a believer in having a service contract. Our old Potterton boiler went wrong a few times and once failed (exhaust fan siezed) at 5pm on Christmas Eve, with lots of family and toddlers due next day. To my surprise, British Gas answered my distress call, and sent an engineer who fixed the problem at 8.00am on Christmas Day.

Our current contract has covered the cost of fitting a new pump on one occasion and a failed motorised valve on another. Nothing to do with the boiler, but both problems were included in the cover and quickly solved problems which occurred during very cold weather. So I'd recommend it.

regards

Howard

[gryffron]

Assuming the boiler is inside the house, at least part of the "waste" heat is contributing to heating the house anyway, even if it isn't going into the radiators. So I concur with previous posters that the saving won't be as much as the efficiency difference implies.

I just had a service, single radiator replaced, heat exchanger de-scale, and two plumbing fixes done for £150 total. So £200pa seems very expensive to me. And the industry providers are infamous for telling you that you need a new boiler when you really don't. But I guess it depends on your ability to find a good freelance plumber. The industry providers are certain to meet a minimum standard I suppose.

Gryff

[Gaggsy]

Thanks for the replies so far. I was really just looking for someone to do the maths. 65% efficient boiler vs 90% efficient boiler. Lazy I know.

Is it as simple as saying this:
My current usage is just over 40,000 KWh and costs just over £1,000 p.a.
1,000 KWh bought and used at 65% efficiency produces 650 KWh.
To produce the same 650 KWh at 90% efficiency requires 722 KWh to be bought (650/90%)
So I should save £278 in gas p.a.
The new boiler installation has cost me £4,236 so it will take over 15 years to pay for it in saved gas.

Am I right?

Anyway, the old boiler was on its last legs. Last year we needed a new gas valve costing £195 to replace. The service was another £90 and the guy had to bring a tap and die set because the screws on the plate were so rusted they had to be drilled out. The pump kept cutting out because the pipes were so clogged with scale and crap it couldn't push water around. This was probably caused by air getting in to the system, too many bends and dead ends added over the years. Pipes had to be cut out and replace and a new pump fitted. This cost me £870. t least three different plumbers had recommended we consider changing the boiler soon. Last month we developed a leak under the hot water cylinder. This was the final straw and we decided to get everything changed.

The boiler has been re-located from downstairs to the airing cupboard upstairs, next to the hot water cylinder. The airing cupboard is inside the family bathroom. Previously it was in the single storey extension at the back of the house that we use as a utility room but probably used to be the coal house and outside toilet. It's single skin brickwork with no insulation so a lot of heat could have been lost. The water also had to travel some distance to get to the cylinder upstairs with more potential heat loss.

I took a reading of 3848 ft3 on the gas meter on 3rd October 2019.
I'll come back in a year's time and tell you the new reading.

Gaggsy

[Dod101]

I must say that I have never had a contract for my boiler. You will get a 7 year or more warranty with the new boiler anyway I would think so do not buy a contract as well. Part of that warranty will of course be that it is serviced annually so the chances of a breakdown should be minimal.

Dod

[Gaggsy]

It's got a 10 year warranty, subject to annual servicing. The installer has done an absolutely brilliant job so far so he will be my first port of call for the servicing.

[Howard]

I must say that I have never had a contract for my boiler. You will get a 7 year or more warranty with the new boiler anyway I would think so do not buy a contract as well. Part of that warranty will of course be that it is serviced annually so the chances of a breakdown should be minimal.

Dod

The terms of most boiler guarantees insist on a service contract. So you have to have one.

In my case the cover for the whole heating system is a few pounds more per year, so it would not be sensible to refuse it. And it has been a good investment, saving a on the cost of a couple of repairs so far.

Boiler manufacturers can be very leisurely in their approach to guarantee repairs. I was quoted two weeks for a repair to my nearly new boiler last winter. Luckily the installer intervened and fixed it quickly.

Regards

Howard

[sg31]

The fitter of my boiler comes back each year to service the boiler at a cost of £60. It's an old house but a completely new heating system fitted 4 years ago. The boiler has a 10 year guarantee and hasn't had any problems so far.

I've always used independent engineers to look after my heating and have no regrets. I've never had a bad one and find them a breed of really honest reliable types. I'm sure there are bad ones so maybe I've been lucky. Being in the building trade does equip one with a good nose for quality tradesmen.

[Dod101]

Well it's up to you of course but in the last few years I have had two new boilers installed in two different houses and the warranty only required annual servicing not a service contract. Cost in the same order as sq31.

I have never paid for a service contract in my life because I consider them a bit of a con. I have a local contractor/boiler engineer who has standby cover for holidays including Christmas and new Year.

Dod

[Howard]

Well it's up to you of course but in the last few years I have had two new boilers installed in two different houses and the warranty only required annual servicing not a service contract. Cost in the same order as sq31.

I have never paid for a service contract in my life because I consider them a bit of a con. I have a local contractor/boiler engineer who has standby cover for holidays including Christmas and new Year.

Dod

I think you are manufacturing a strawman argument.

My service contract is not expensive. Why are you suggesting that it is?

It's a few pounds more than sq31's.

It is actually an insurance contract which costs a similar price to (and includes) an annual check. What's wrong with that? I thought you made your previous living from insurance? And yet you are arguing about spending a few pounds extra for peace of mind.

regards

Howard

[Dod101]

There is no need to get so worked up about this. As I said it is up to you. As far as insurance is concerned I think a lot of people spend far too much on it. I was listening for instance to a consumer programme on the radio in my car the other day. The matter concerned buying so called gap insurance when buying a new car, and the discussion was whether you should look independently to buy it or just take the deal offered by the car dealer. What was not touched on was whether it was worth buying gap insurance in the first place. Like may of these add ons, (like boiler insurance) I have never bought it in my life although I buy a new car every five years or so. I know that that is also a waste of money in some people's eyes but that is another discussion.

I never tried to sell anything that I did not believe in. It is though entirely up to you and if it gives you peace of mind then it is obviously worth while for you.

Dod

[quelquod]

Re Gaggsy’s original question I doubt if comparing quoted (even SEDBUK) efficiencies will give the real answer as it depends on the installation and usage. FWIW I put off replacing our 1978 Ideal boiler until it started a small leak a few years ago. The new one is a Vaillant (not a combi) and our gas usage has dropped by around 35% (4-year average against previous 11-year average). Obviously it’s a bit dependent on average temperatures etc. But that has included last year’s ‘Beast from the East’.

Also FWIW I don’t have a service contract. Vaillant’s lengthy guarantee only requires an annual service.

[MyNameIsUrl]

FWIW I put off replacing our 1978 Ideal boiler until it started a small leak a few years ago.

Was this a water leak, gas leak, or flue leak, if you don't mind my asking? I'm still putting off replacing my 1977 Ideal boiler, wondering what reason will be compelling enough to trigger a replacement.

[PrincessB]

Would anyone know how to do a rough calculation, all things being equal?

We had a a similar discussion about this some months ago.

From what I understand from the various energy efficiencies of differing structures, your calculations are more comparative when you work out how much energy you use for each square metre of interior space.

My elderly, but relatively well insulated pile of bricks is about 110 square metres and gas usage over the last year was 10,200 kWh (so says my smart meter).

I've got fewer radiators than you, eight, or seven if you count the one that's only turned on when it's really cold. Bathroom is heated electrically and I can't extract the usage of a 1kW wall heater from my overall electric consumption - We use about 70kWh electric per week, no solar panels.

Rounding off the numbers, I'm using 93kWh for gas and 33kWh of electric for each square metre per year.

Hope this helps.

Regards,

B.

[Gaggsy]

UPDATE:

Well, I've had the Ideal boiler for a year now and it's been fine. No problems.
I took a reading of 5026 on its birthday ( ) and it looks like I've used about 37,000 KwH in the year. So, a 7.5% drop in usage and a saving of only £86 for the year.

At this rate it'll take nearly 50 years for the investment to pay off!
Ah well, the house is now nice and warm and the heating is reliable.

Cheers
Gaggsy