New boiler uses more gas than 16 yrs old boiler.

victor2

As already said, it has been colder lately this year when compared to last.
Comparing the minimum overnight temperatures where I am for Dec 1 to 21 this year, it has averaged 0.9C.
For Dec 1 2011 to Mar 31 2012 (the period you are comparing to), the average was 1.7C. That's in the Midlands.

HappyMJ

HTC wrote: »

The old boiler is Halstead Quattro Gold combi fan flue boiler. We tried to find the rating of this but couldn't. The new one is Worcester Greenstar 30si and its efficiency is 90.1%

Suppose the boiler's efficiency is 90% but it uses more gas. We understand this theory but then it is a con!

Old boiler was about 80% efficient....

It should all things being equal reduce your gas usage from the average 16,500kWh down to 14,650kWh a saving of 1,850kWh....at your secondary rate of...let's say 3.5p/kWh last year and 4.0p/kWh this year...

This should cost you £8.50 more than last year. Great isn't it....

gas4you

Do you live in a mansion?

That is a very big boiler for an average house.

Most houses would not need more than 18Kw.

HappyMJ

gas4you wrote: »

Do you live in a mansion?

That is a very big boiler for an average house.

Most houses would not need more than 18Kw.

Boilers are sized for the hot water demand. A 30kW boiler will output enough water for 2 showers at the same time maybe the OP has a bathroom and an ensuite.

Perry525

HTC wrote he has used 88% more "gas" than the previous year.

That is one hell of a jump!

It cannot be explained away - by a price increase!

closed

it can be explained by a mathematical error, or different periods, or estimated bills

C_Mababejive

New combi does not automatically equal lower gas bills.

My 30 year old boiler has an input of 12kw.

The house gets lovely and warm and i have all the hot water i want. Why then would i bother having a combi fitted which has a max input of maybe 30 or 40 Kw ?

Efficiency? Well what is meant by efficiency? The term is banded about with gay abandon but what does it really mean?

Linton

C_Mababejive wrote: »

New combi does not automatically equal lower gas bills.

My 30 year old boiler has an input of 12kw.

The house gets lovely and warm and i have all the hot water i want. Why then would i bother having a combi fitted which has a max input of maybe 30 or 40 Kw ?

Efficiency? Well what is meant by efficiency? The term is banded about with gay abandon but what does it really mean?[/QUOTE]

The % of heating that doesnt go up the flue?

rogerblack

C_Mababejive wrote: »

Efficiency? Well what is meant by efficiency? The term is banded about with gay abandon but what does it really mean?

Simply power in versus power out.
Your old 12kW out boiler may need 17kWh/h of gas input (if 70% efficient.
A new 85% efficient boiler may use 14kWh/h of gas in.

At current prices that's around 7p or so saving per hour it's on full.

In many cases, this saving will not be worthwhile, and in some cases a new boiler won't reach its 'sticker' figures.

If you're spending 1000/year on gas - the saving is 'only' around a hundred pounds a year or so.

If it's a straight boiler swap, and it goes well, that might in principle pay back after a decade.
If it gets more complex, or if the boiler does not perform to spec, payback is more questionable.

gas4you

HappyMJ wrote: »

Boilers are sized for the hot water demand. A 30kW boiler will output enough water for 2 showers at the same time maybe the OP has a bathroom and an ensuite.

Sorry, yes I agree.

Quickly looked at it and took the 'Si' wrongly as a system boiler.