kWh per m2 per annum

[Oz07]

In light of @AliG recent thread I want to know what everyones using per m2 to heat/heat and water/ heat and water and cook in their home

 

I'm a neanderthal so i've just multiplied the gas meter units by 11 to get kWh, seems to get close enough to the figures on the bill. I've got 5 months of bills to work with but should be pretty even between heating months and non heating months up to now.

 

I am at 68 kWh per m2 and that includes heating, hot water and cooking on hob.

Edited December 6, 2020 by Oz07

[Declan52]

How do you work it out??

[Oz07]

Got my total units used for the 5 months, multiplied by 11, divided by 5, multiplied by 12 then divided by sq metre. Have i dropped a clanger?

Not sure how you would work out if using elec

[Declan52]

But what do the  11,5,12 stand for.

[Oz07]

Well yours will be different you have a years worth of bills?

On my estimated gas bill if I multiply the units on meter by 11 it gets me to roughly the right kWh. 

I've been in 5 months upto now. 

12 to get me per annum

[SteamyTea]

1 minute ago, Oz07 said:

Not sure how you would work out if using elec

Easy, log the data and divide by square meters.

A number of things spring to mind, how have you calculated the area, what external temperatures are you working with, is the house permanently occupied, solar gain, detached, terraced, bungalow.

 

A few years back, we did this over  at the other place, go have a look, the data is still there, and it is quite detailed.

 

Biggest problem I found was that people wanted to measure things differently, i.e PV contributions, not splitting up gas and electric, etc

[Oz07]

I knew you'd pop up with something like that! There are a lot of variables but if people are genuine it should give a overall picture. I'm using net internal m2. If anyone has a wood burner would be good to say! I think my figure may need honing with exact dates I was very rough and ready to start with. 

[Oz07]

Im detached bungalow but would expect 2 storey houses to count both floors like you would a valuation or in the most popular thread £ build cost per m2

Edited December 6, 2020 by Oz07

[Declan52]

Ok so I use wood pellets and going by Google they produce 4.9kwh of heat per kg. I average around 1200 kg of pellets a year and my house is 220sqm. So this gives me 26.7 kWh per M2. This is for heating and dhw needs for a family of 5.

My electric usage each year is covered by my PV system. Last year my bill was £589 but I got £636 back so not sure how to add that to the total.

[Oz07]

My god I'll have to knock this place down and start again. @AliG what are you all totted up heat and water per m2?

D

@Declan52 No need for electric figures if you use pellets for heat and water. Elec will just muddy the waters

Edited December 6, 2020 by Oz07

[nod]

Not sure of the units But I’m reliably informed that we are averaging £35 per month gas and electric 284m2 Traditional built no PV or MVRH 

[Oz07]

Piss poor effort @nod just confuses things. Dig out a bill and give us some kWh I've seen the coat you make your missus sit on the sofa in!

[Ferdinand]

Think putting in amount of kWh generated by solar will be useful context, even though we cannot exactly work out how much is captured.

[Oz07]

Why is that useful? I want to know consumption not generation. I bet these solar farms generate a lot of leccy but wouldn't be very comfortable living underneath a panel

[Ferdinand]

30 minutes ago, Ferdinand said:

Think putting in amount of kWh generated by solar will be useful context, even though we cannot exactly work out how much is captured.

 

Quote

Why is that useful? I want to know consumption not generation. I bet these solar farms generate a lot of leccy but wouldn't be very comfortable living underneath a panel

 

Because any you generate and use internally reduces your metered consumption materially. So affects the number we are talking about for anyone with a grid tied solar. eg Mine generates about 5 MWh per annum, which does not go through my meter. I need to check the units before I post my meter numbers to the thread. 

[Oz07]

Sorry @Ferdinand I see what you're saying. Yes it effects the figures in that case. 

[Ferdinand]

Just now, Oz07 said:

Sorry @Ferdinand I see what you're saying. Yes it effects the figures in that case. 

 

Thanks.

 

I'm saying put the numbers in so we can see and adjust if we need, but as a separate line. 

 

You could argue the same for anyone who charges a vehicle which will make a material difference, or non-connected generation, but at present I think more here probably have connected solar so that is the important one.

We could all have huge banks of off-grid solar and be keeping quiet, just to make you feel bad ?.

 

F

[Oz07]

That's why wood burning people have got to declare also. Would skew the figures otherwise. I'm beginning to be convinced these mvhr systems significantly increase your heating need. Either that or mine is not working properly. I haven't balanced it yet but will do when I get time to put the replacement unit up. 

[nod]

11 minutes ago, Oz07 said:

That's why wood burning people have got to declare also. Would skew the figures otherwise. I'm beginning to be convinced these mvhr systems significantly increase your heating need. Either that or mine is not working properly. I haven't balanced it yet but will do when I get time to put the replacement unit up. 

At the end of the day it matters only what you are paying in £ per annum 
We will look at MVRH on the next one I still don’t see how PV could pay for itself Certainly with low energy bills to start with Our Sap 

predicted an annual saving of £250 Do The math

 

[nod]

18 minutes ago, Ferdinand said:

 

Thanks.

 

I'm saying put the numbers in so we can see and adjust if we need, but as a separate line. 

 

You could argue the same for anyone who charges a vehicle which will make a material difference, or non-connected generation, but at present I think more here probably have connected solar so that is the important one.

We could all have huge banks of off-grid solar and be keeping quiet, just to make you feel bad ?.

 

F

My wife’s job is  in a freezing operation theater al day so won’t have the heating more than 19 and goes round opening windows 

Hence the MVRH 

She also thinks I’ve gone overboard on the insulation 

But I’m convinced that making the house airtight and well insulated is far more important than the way we choose to heat our homes 

 

Our previous home was built in the 90 s Just over half the size but cost more than double to heat 

 

PS we have a wood burner but due to contracting COVID back in January and still suffering the effects we haven’t used it for 12 months 

[Oz07]

I think kWh is a much more standardised measure. Would it have a clue what Declan pay a for pellets but we can see that his house consumes lot less than mine. If you're on gas be easy to work out

[Declan52]

27 minutes ago, Oz07 said:

I think kWh is a much more standardised measure. Would it have a clue what Declan pay a for pellets but we can see that his house consumes lot less than mine. If you're on gas be easy to work out

They average £280 per tonne. Been as low as £240 recently and as high as £340. They fluctuate to keep track of oil prices. 

[Hobbiniho]

Ok i will play, 85m2 house built in ~1880 half refurbished, not exactly loads of insulation and far from airtight, ASHP feeding radiators/ fan rads 255L UVC, consumption is 42.8KWh/m2/year, generation is 89.6KWh/m2/year. 

 

The figures are higher than they should be, because for the first ~ 4 months of the year the hot water was being heated to 55 and the ASHP was in weather comp mode, i have since changed the hot water to 48 and set a direct temp of 38 from the heat pump i maintain the rooms at 20 degrees, planning to refurb the back extension next year which will sort out most of the poor/ missing insulation and draughts

[Mr Punter]

Gas heating, DHW and hob has worked out at 60KWh/m2/year here averaged over 3 years.  I suspect we don't bath and shower much though.

[Mr Punter]

The SAP for here has the same 60KWh/m2/year for "current primary energy use" but the estimated heat demand (space heating + water heating) works out at 35KWh/m2/year.  Not sure how the figures relate.