Used well, and generated from renewable sources, electricity is in the long run more efficient once it is in your house.
The Peveril Solar house (during this coldest December since 1910) is using 27-29 kWh / day to provide space heating and hot water for this house, and a neighbour with a well insulated house of similar size, but with gas central heating and DHW is using about 120-140 kWh / day of gas to achieve the same comfort.
With regard to Climate Change, what matters finally is the amount of CO2 you emit from heating your house and other activities, such as transport and food purchasing decisions.
Quote 16 Dec: 'A Task Group convened by the Zero Carbon Hub has delivered a report to the Minister for Housing and Local Government setting out its recommendations for carbon compliance levels for new homes from 2016. Carbon Compliance – that is, on-site reductions in emissions – form part of the Government’s overall plan for achieving zero carbon homes; the other part comprises off-site "allowable solutions."'
for the details.
Their recommendations are that the 'built performance' emissions from new homes should not exceed:
- 10 kg CO2(eq) /m2/year for detached houses
- 11 kg CO2(eq) /m2/year for other houses
- 14 kg CO2(eq) /m2/year for low rise apartment blocks
Conversion to CO2e (gross CV basis)
- Grid electricity: 1.0 kWh =0.544 Kg CO2 per unit
- Natural gas: 1.0 kWh 0.184 Kg CO2 per unit
- Peveril house is costing (during these coldest winter days) 27-29 x 0.544= 14.6 - 15.8 kg/day
- Neighbour's house in the same time period 120-140 x 0.184 = 22 - 26 kg/day
During the year 1 Oct'09 to 1 Oct'10, our House Space Heating requirement was 3,000 kWh = 1632 kg of CO2. For 120 sq metre house, that is 13.6 kg / sqm / year. considering that this is a developer built house with insulation only slightly better than the current building regulations, and not having MVHR (Heat Recovery), that is pretty good!
The Passivhaus requirement is for 15 kWh /sqm/year or 8.16 kg of CO2/sqm/year, so we are still far from that target.
Our PV roof generated 3,325 kWh in the same time period, which was all either used by us or sent to the Grid for others to enjoy. This is equivalent to reducing CO2 emissions by 1809 kg/year.