kWh per m2 per annum

[DamonHD]

76m^2

 

Last year consumption and generation figures:

 

http://www.earth.org.uk/saving-electricity-2019.html

 

1992kWh e (consumption), 3855kWh e (generation), 3157kWh gas (DHW + spac heat).

 

So final energy per m^2

  * ignoring generation, exergy, carbon intensity, etc: 68kWh/m^2

  * allowing for generation: 17kWh/m^2

  * space heat alone (allowing 4kWh/d for DHW): 40kWh/m^2 for space heat

 

Rgds

 

Damon

[ProDave]

Mine comes out at 1648kWh for the year, that's not any estimate, that's the current real world measured electricity usage.  It's about 150 square metres so 11kWh per square metre.

 

That's the electricity driving an ASHP so in terms oh heat input assuming a COP of 3 that would be 33kWh of heat per square metre per year.

 

I hope that figure will drop when we finally get the sun room complete as I hope that will be able to add some solar heat into the house on a sunny day.

 

Solar PV generation exceeds that amount.

[Thedreamer]

Been in the house for nearly 6 months, but coming in at 25.92

 

That me taking the electricity energy units 1815 units / 6 x 12 / 140.

 

3 hours ago, Oz07 said:

That's why wood burning people have got to declare also. 

 

 

Yes, I need to declare this, burn a trug of free logs each night as well.

[Oz07]

@Mr Punter do you have mvhr? In terms of usage my missus likes baths, I'm in the shower for minimum 20 minutes every night and we have thermostat set at 20. 

 

My last place was 1.5 storey 6"pir below b&b 6" dritherm 34 in cav and about 8"pir in vaulted ceiling with a small area of flat ceiling 350mm earthwool. I feel like the boiler worked less to keep that the same temp. I do remember Jeremy saying 1.5 storey most efficient shape house?

[A_L]

2 hours ago, Mr Punter said:

Not sure how the figures relate.

 

Essentially it is the fuel 'efficiency' of putting usable energy into the house. e.g. It takes 1.22kWh of primary energy (where gas is the fuel) to put 1kWh of heat into the house. It takes 3.07kWh of primary energy (fuel) to put 1kWh of electricity into the house. N.B. certain electrical consumption e.g. appliances are not included in SAP

[Oz07]

@ProDave do you have a separate meter on the ashp side of the leccy?

[ProDave]

34 minutes ago, Oz07 said:

@ProDave do you have a separate meter on the ashp side of the leccy?

Yes I specifically installed another electricity meter to measure what we use for heating.  This shows "other stuff" in the house uses at least twice as much as heating the house.

 

PV generation exceeds heating usage, but does not quite cover heating and DHW

[Oz07]

Good idea

[Oz07]

Is your water ontop of your figure then? Ie just for heating

[SuperJohnG]

These figures seem pretty low....

 

 

I'm 24'650 kWh for the year (estimated by my supplier - but I double checked and ita accurate). 

 

House is 90m^2 internal area. 

 

So 274kWh/m2/year which seems horrific compared to others here. Bearing in mind, this is my current house that we live in, which is a 1975 thermaltite block house with brick outer skin, no insulation in walls. Insulation above upstairs ceilings but cold loft. Air bricks in walls, family of 4. 

 

Thats all our gas usage for heating, hot water and cooking. 

 

I'm looking forward to living ona SIPS house with insulated foundation...

Edited December 6, 2020 by SuperJohnG

[Thedreamer]

10 minutes ago, SuperJohnG said:

These figures seem pretty low....

 

 

I'm 24'650 kWh for the year (estimated by my supplier - but I double checked and ita accurate). 

 

House is 90m^2 internal area. 

 

So 274kWh/m2/year which seems horrific compared to others here. Bearing in mind, this is my current house that we live in, which is a 1975 thermaltite block house with brick outer skin, no insulation in walls. Insulation above upstairs ceilings but cold loft. Air bricks in walls, family of 4. 

 

Thats all our gas usage for heating, hot water and cooking. 

 

I'm looking forward to living ona SIPS house with insulated foundation...

 

Lucky you have mains gas, if that was oil would be costing a fortune.

 

A modern self build needs hardly any heating.

[SuperJohnG]

4 minutes ago, Thedreamer said:

Lucky you have mains gas, if that was oil would be costing a fortune.

My childhood home was oil-fired central heating, house likely 400-450 sqm. We had a 10'000L stainkess steel oil tank.. (it was actually a milk tank). We used to fill it when it was 10-15p a litre. A few years ago I was offered the house by people who bought it from us as a first refusal. I quickly done the calc for heating oil....which then was around 70p...and realised I couldn't afford to live there.  ?

[SteamyTea]

I have just updated my monstrous spreadsheet of my energy usage.

My daily mean usage is, so far this year, 11.3 kWh, so that will be 4,125 kWh for the year.

Floor area (total internal) is 48m².

So that will work out at.

 

4125 / 48 = 86 kWh.m^-2.

 

 

[ProDave]

1 hour ago, Oz07 said:

Is your water ontop of your figure then? Ie just for heating

Yes that's just space heating.  DHW is on top of that.  I don't see the point of relating DHW useage to square metres. That is a function of how many people not how big and well insulated the house is.

 

And just to clarify this is not energy usage for "stuff" either.  The non heating and non DHW electricity used here is roughly double heating + DHW.  So if all my heating and DHW dropped to zero, the electricity bill would go down by about 1/3

 

This compares to our previous house where our electricity usage was about the same as our total here but in addition at the old house we were spending over £1000 on oil every year.

[Oz07]

I'll be interested to see if mime reduces on a per annum basis. Sap estimates closer to 40kwh m2

@ProDave Good point about hot water not being anything to do with house performance per se. Unfortunatley i can't separate mine unless I start measuring things. 

Still no comments on if mvhr increases your heating demand. Even allowing for opening bathroom Windows and running extractor for 40 mins a day in the old place I suspect the mvhr system here gives me more loses over 24hr. So much for heat recovery!

[Oz07]

27 minutes ago, SteamyTea said:

I have just updated my monstrous spreadsheet of my energy usage.

My daily mean usage is, so far this year, 11.3 kWh, so that will be 4,125 kWh for the year.

Floor area (total internal) is 48m².

So that will work out at.

 

4125 / 48 = 86 kWh.m^-2.

 

 

Does that include all electric or heating and dhw ?

[Ferdinand]

7 minutes ago, Oz07 said:

 

Still no comments on if mvhr increases your heating demand. Even allowing for opening bathroom Windows and running extractor for 40 mins a day in the old place I suspect the mvhr system here gives me more loses over 24hr. So much for heat recovery!

 

I set the boffins on this some time ago wrt my trickle fans (HR and not HR) which lose more energy than MVHRs, and the amount of heat than can be carried in the volume of air put out by an MVHR - once you have allowed for the 70-90% of heat that is recovered - makes it quite negligible in terms of the actual numbers. 

 

IIRC it is of the order of 10s of £££ per year at most.

 

It may be in a thread in Boffins' Corner somewhere.

 

F 

[Oz07]

Is the sane argument not made in reverse though for picking mvhr over extractor, as in extractor expel a lot of air you've paid to heat?

[Ferdinand]

13 minutes ago, Oz07 said:

Is the sane argument not made in reverse though for picking mvhr over extractor, as in extractor expel a lot of air you've paid to heat?

 

 Yes - but in my case my house is a full reno (3 walls and a hole in the ground)  which does not reach "near passive" level from 10 years ago by somebody else to make a chalet bungalow with a warm roof, so I can't fit an MVHR without huge dismantling - so I went for a PIV loft fan upstairs and a HR trickle unit downstairs. Not ideal, but the best I can do.

 

Were I building new, I would be going near passive and MVHR.

 

Love the typo - "sane argument". That's usually the one I'm not making ?.

 

F

 

[Hobbiniho]

Interesting point regarding the DHW usage, i suppose mine is relatively low as i am a single man so will use not a lot of hot water, redoing the figures takes my consumption down from 42.8KWh/m2/year to 39.9KWh/m2/year and generation from 89.6KWh/m2/year to 81.7KWh/m2/year

 

For the argument about MVHR i always understood it to be more about having a basically net 0 gain/loss in heat its heat recovery not heat addition, normal extractors dump hot air outside and replace it with cold through trickle vents, MVHR uses outgoing air to heat the incoming air to inside temperature. People that i speak to that have MVHR say they are amazed at the air quality and overall "freshness" and lack of condensation.

Edited December 6, 2020 by Hobbiniho
KWh

[PeterW]

2 hours ago, Hobbiniho said:

MVHR uses outgoing air to heat the incoming air to inside temperature

 
That is only partially true - you get a maximum 80-85% transfer which means that when you have a delta of 16°C between inside and outside you will only be getting 13°C uplift. This means you can soon start cooling the air in a house when it Is only 4°C outside. 

[SteamyTea]

8 hours ago, Oz07 said:

Does that include all electric or heating and dhw ?

That is all, I shall try and split it up later into DHW, space heating and 'the rest'.

[Mr Punter]

14 hours ago, Oz07 said:

@Mr Punter do you have mvhr?

 

No.  Extracts x 6 plus trickle vents.

[ProDave]

The thing with mvhr is you get constant fresh air all the time at a controlled rate which you can adjust. 

 

Trickle vents and bathroom, / kitchen extractors are just uncontrolled holes in the house fabric and on a windy day will likely grossly over ventilate the house and of course with no heat recovery.  At our last house we had 3 bathroom extractors, utility extractor, kitchen extractor, stove flue (stove drew it's air from the room) A vent in the floor behind the stove to let air in for the stove to burn, a letterbox in the front door and a cat flap.  It was clear on a windy day that the house was very much harder to heat, and if you opened a door or a window a gale blew through the house with all these holes in it.

 

By comparison the new house has no holes like that, it is all sealed up, the stove has it's combustion air ducted in and not from the room, no letterbox and no cat flap.  Open a door here on a windy day and no gale blows through, and the house is no harder to heat on a windy day to a still day.

[Mr Punter]

9 minutes ago, ProDave said:

Trickle vents and bathroom, / kitchen extractors are just uncontrolled holes in the house fabric

 

The outside terminals on mine have backdraught flaps and the fans have an iris that opens when the fan runs.  Not as good as MVHR but I could not find space for the unit and all the ducting, plus over 4 storeys there would need to be lots of acoustic and fire stopping.

 

Also, I like an externally ducted kitchen extractor.  The recirculating ones don't do it for me.