How much KW of gas does your combi use per hour?

richardjones9191

Hi Everyone, 

I recently had a smart meter installed and have been seeing how much gas is used per hour to heat up my 3 bed semi detached home with 10 Rads. I currently have a standard boiler system so tank in the loft and tank in the airing cupboard. Boiler is an 18 year old Potterton Suprima 30l. 
I noticed it uses around 11KW per hour when heating the house and around 100 watts of electric whilst it is functioning. 

I was wondering how much more efficient would having a combi boiler be basically and do they use less gas per hour?

Or if anyone has switched to a combi recently and noticed the difference in usage?

Weird question I know.

Thanks everyone

Gerry1

Welcome to the forum.

You need to understand the units.  It's not 11kW per hour, it's 11kWh per hour which of course is plain 11kW.

In other words, the power is equivalent to eleven single-bar electric fires. or 110 old-style 100W lightbulbs.

The manual shows that the Potterton Suprima 30L has an input of 11kW and an output of 8.8kWh so it's 80% efficient.

[Deleted User]

Unless you have a very draughty uninsulated home, your boiler will not be using 11kWs per hour constantly. As you have a smart meter, I suggest that you download the App BRIGHT. If your meter profile is HH, then you will get a graph similar to the graph below. My wife and I are at home all day in a 4 bedroomed property with 14 radiators. We use gas for HW re-heating; central heating and cooking. We run our boiler with a flow temperature of 65C with a hot water cylinder temperature of 60C.

richardjones9191

Gerry1 said:

Welcome to the forum.

You need to understand the units.  It's not 11kW per hour, it's 11kWh per hour which of course is plain 11kW.

In other words, the power is equivalent to eleven single-bar electric fires. or 110 old-style 100W lightbulbs.

The manual shows that the Potterton Suprima 30L has an input of 11kW and an output of 8.8kWh so it's 80% efficient.

Hi Gary, thanks for your reply, sorry yes my gas usage was 11KWH for every hour it is functioning. I was wondering if the usage would be higher as I use the new boiler quotes and they all offer 24kw boilers and not sure if that is going to draw more gas or not. Sorry not massively clued up on how it all works! Thanks for the advice too.

Gerry1

Dolor said:

Unless you have a very draughty uninsulated home, your boiler will not be using 11kWs per hour constantly.

Unless you have a very draughty uninsulated home, your boiler will not be using 11kWs per hour constantly.

FTFY !

QrizB

Welcome to the forum.

I don't think a combi will save you anything on space heating; combi boilers heat radiators in the same way that regular ones do.

A new boiler might be slightly more efficient than your old one, although any savings are likely to be marginal.

Disclosure: my boiler is regular.

RelievedSheff

We have a 3 year old detached house running a 30kW Ideal Combi boiler with 10 radiators. 

I am currently working from home and for the last couple of days have had the heating on all day as it has been a bit chilly. Yesterday we used 42kWh of gas, today looks set to be a similar amount. 

When it isn't quite so cold outside and I don't have the heating on all day a more normal figure for our house is around 30kWh of gas at this time of year.

richardjones9191

*Gerry sorry not Gary

richardjones9191

RelievedSheff said:

We have a 3 year old detached house running a 30kW Ideal Combi boiler with 10 radiators. 

I am currently working from home and for the last couple of days have had the heating on all day as it has been a bit chilly. Yesterday we used 42kWh of gas, today looks set to be a similar amount. 

When it isn't quite so cold outside and I don't have the heating on all day a more normal figure for our house is around 30kWh of gas at this time of year.

Hi thanks for you reply, That seems very good! I have just checked my smart meter and so far it has used 19kwh of gas today and heating has only been on for 1 hour 30 mins. Seems my boiler is highly inefficient perhaps.

Astria

Don't worry about the difference between a normal boiler and a combi boiler, worry about the efficiency of your boiler.

Check the SEDBUK rating of your boiler to easily compare.

Mine is stated as 'A' as is 88.6% efficient.

The Potterton Suprima that you mention has a rating of 78%.

The most I've seen is 91%.

All these figures depend on everything being ideal of course, so all figures could be lower in reality.

Before you start ripping out a good working boiler, consider how much you could save compared to how much it costs to replace.

richardjones9191

Astria said:

Don't worry about the difference between a normal boiler and a combi boiler, worry about the efficiency of your boiler.

Check the SEDBUK rating of your boiler to easily compare.

Mine is stated as 'A' as is 88.6% efficient.

The Potterton Suprima that you mention has a rating of 78%.

The most I've seen is 91%.

All these figures depend on everything being ideal of course, so all figures could be lower in reality.

Before you start ripping out a good working boiler, consider how much you could save compared to how much it costs to replace.

Hi Astria, very good point. I was mainly wondering what the difference in usage would be to a newer more efficient combi boiler but potentially not that much difference it seems. My only con with not having a combi is you can run out of hot water sometimes but mostly manageable! Thanks everyone for their replies, I really appreciate them.