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| * Heating <= 3,660 kWh/m² over the year. | | * Heating <= 3,660 kWh/m² over the year. |
| * Total primary energy need <= 14,640 kWh/m² over the year. | | * Total primary energy need <= 14,640 kWh/m² over the year. |
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| This year is a little weird, because we had the windows replaced while it was 2.5°C. But our heating is currently 3,270 kWh
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| and total energy use is 8,100 kWh.
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| So, getting there.
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| Why work this out? Well, that is what EPC certificates work towards, they tell you how far you are from the Passivhaus standard and give you an idea of how far you have to go!
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| These days, it's important information to have, not least because it is what our energy companies do to work out what your direct debit needs to be.
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| Because we're only using electricity, and electricity is £0.2527 per kWh. So, so far this year we have spent £(0.2527*3,270) or £826.33 on our heating and hot water.
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| Our total usage has been £2,046.87, so outside of our heating, we've spent £1,220.54.
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| Only we haven't, have we? Our solar generation has taken 3.7 MWh off thia total. That means we've only bought 4.4 MWh or 4,400 kWh => £1,111.88. For everything. Cutting the grass, lighting our house, driving the car, powering the bidet loo.
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Revision as of 17:10, 22 November 2025
The standard says,
- Space heating <= 15 kWh/m²/yr,
- an airtightness limit of 0.6ACH@50Pa (air changes per hour at 50 Pascals),
- total primary energy demand <= 60 kWh/m²/yr.
For our house, at 244m² this works out at:
- Heating <= 3,660 kWh/m² over the year.
- Total primary energy need <= 14,640 kWh/m² over the year.
