Is our Combi using too much gas?

grumpycrab

We've an old combi (Baxi 105e) which seems to be using gas at a very high rate (should have checked this years ago but you know what it's like...).
The basics - our house is a small detached property from the 50's - has cavity filling in theory - 3 walls of living room are external; we have hard wood windows frames with double glazing.
When the CH is running the combi consumes about 0.72 units/hour (readings taken directly from the metric meter); this is about 8kWh according to
https://www.businessenergy.com/gas/kwh-calculator.html
That's running about 3 large rads and 4 smaller rads.
The only check I've done is the CH thermostat on the boiler which is about half way (50%); rads get hot but not scalding.

New boiler cost sends me into a panic; any suggest appreciated (keep it simple please.)

Billy_the_fish

Not sure in terms how much energy is OK per hour for an efficient boiler.

But, heres a page with your boiler details on.

Says its a D rated combi. 78% efficient.
So effectively, around 25% of your gas bill is wasted energy.
https://www.homeheatingguide.co.uk/efficiency-tables?model=008357

Also,(Someone correct me if im wrong please), meters can be metric or imperial.

If your boiler is in-efficient, then only buying a new efficient one will solve the issue (Although, that maybe not the case)

But that said, knowing your boiler runs on average 75% efficient (Give or take a few percent), and lets say you spend £500 a year just on gas, then thats £125 wasted on inefficiency.

Over a few years, a new A or B rated boiler will pay for itself.

Not sure if there is an efficiency test that can be carried out by an engineer or not. Something you would maybe have to research/Google.

Billy_the_fish

To add, depending on your personal situation you maybe able to get help with buying/installing a new combi boiler.
https://www.boilergrants.org.uk

JohnB47

grumpycrab wrote: »

We've an old combi (Baxi 105e) which seems to be using gas at a very high rate (should have checked this years ago but you know what it's like...).
The basics - our house is a small detached property from the 50's - has cavity filling in theory - 3 walls of living room are external; we have hard wood windows frames with double glazing.
When the CH is running the combi consumes about 0.72 units/hour (readings taken directly from the metric meter); this is about 8kWh according to
https://www.businessenergy.com/gas/kwh-calculator.html
That's running about 3 large rads and 4 smaller rads.
The only check I've done is the CH thermostat on the boiler which is about half way (50%); rads get hot but not scalding.

New boiler cost sends me into a panic; any suggest appreciated (keep it simple please.)

Not sure what you mean by CH thermostat at 50%. Do you mean a thermostat on the boiler itself? If so, that is one that controls the temperature that the CH water reaches before the boiler stops firing. Then it waits until the water cools and fires up again.


Do you have a room stat and if so what is it set at?


If I were you, I wouldn't worry too much about the gas being used while the boiler is fired up (if that's what you mean). Better to take readings at the same time every day, to get a better handle on things.

molerat

Billy_the_fish wrote: »

Over a few years, a new A or B rated boiler will pay for itself.

Slightly flawed logic there as by the time it is paid for it will most likely need replacing.

grumpycrab

JohnB47 wrote: »

Not sure what you mean by CH thermostat at 50%. Do you mean a thermostat on the boiler itself? If so, that is one that controls the temperature that the CH water reaches before the boiler stops firing. Then it waits until the water cools and fires up again.


Do you have a room stat and if so what is it set at?


If I were you, I wouldn't worry too much about the gas being used while the boiler is fired up (if that's what you mean). Better to take readings at the same time every day, to get a better handle on things.

Re. CH thermostat on boiler - its just a dial with a rad symbol - a crudeway of setting the rad water temp I believe.

Room stat (in small hall way) is set to 18degC - its the coldest area of the house! When it gets to 18deg (via hall way rad that does not have its own thermostatic valve) the living room is about 20deg.

** I agree I need to provide a daily usage because I think its much higher than my hourly rate indicates. I will do that. Am tempted to delete my orignal post now. Sorry if I've wasted any time.

Anthorn

grumpycrab wrote: »

We've an old combi (Baxi 105e) which seems to be using gas at a very high rate (should have checked this years ago but you know what it's like...).
The basics - our house is a small detached property from the 50's - has cavity filling in theory - 3 walls of living room are external; we have hard wood windows frames with double glazing.
When the CH is running the combi consumes about 0.72 units/hour (readings taken directly from the metric meter); this is about 8kWh according to
https://www.businessenergy.com/gas/kwh-calculator.html
That's running about 3 large rads and 4 smaller rads.
The only check I've done is the CH thermostat on the boiler which is about half way (50%); rads get hot but not scalding.

New boiler cost sends me into a panic; any suggest appreciated (keep it simple please.)

Energy usage is subjective because there are a lot of variables not least of which is how much it's used. As far as I know gas boilers can waste as much as 30% energy. I have seen it stated that electric boilers are more efficient that gas boilers but the balancing factor is that gas is cheaper than electricity.

According to the British Gas article which I have linked below, your thermostat is set too low and should be at 80% if you have a single dial.
https://www.britishgas.co.uk/home-services/boilers-and-heating/guides/boiler-efficiency.html

My own combi boiler is very efficient and is more likely to waste water than gas which is important if you have a water meter: I can fill the kitchen basin with water until I get hot water coming through especially if the central heating is not being used at the same time.

Lastly check with your local authority to see if you can get a grant to replace your old boiler with a more efficient, modern boiler.

molerat

Billy_the_fish wrote: »

Over a few years, a new A or B rated boiler will pay for itself.

But by the time it is paid for it will most likely need replacing. Replacing a boiler to save on energy use is rarely cost efficient.

grumpycrab

Anthorn wrote: »

According to the British Gas article which I have linked below, your thermostat is set too low and should be at 80% if you have a single dial.

Great. will check.

Anthorn wrote: »

I can fill the kitchen basin with water until I get hot water coming through

The downside of efficiency

Billy_the_fish

molerat wrote: »

Slightly flawed logic there as by the time it is paid for it will most likely need replacing.

Not if well serviced.

The alternative is maybe, running an old boiler that may actually be only 50% efficient.

The logic is leaning more towards a better rated boiler, i.e. An A rated boiler instead of a D rated boiler.

If you disagree though, thats fine.

matelodave

If you use Billy's logic and you pay say £500 a year for your gas and your boiler is only 75% efficient than theoretically you could save £125 a year.

However a shiny new boiler is still only around 90% efficient so in reality you'd only save around 15% of £500 = £75 but lets be generous and say you save £100/year.

A new boiler will cost you the thick end of £2000 so if it lastes 20 years you'll just about break even but it's highly unlikely that a new boiler will last much more than ten years.

IMHO you'd be better off keeping the existing one going as long as you can and putting some money away for when it does finally turn up it's toes.