If you've ever wondered how efficient UK housing stock is, take a look at the two charts below. They show the proportions of homes that achieve each Energy Performance Certificate (EPC) rating in England and Scotland.
The EPC is a calculation that takes features of a house (its size, window area, insulation values for walls, floors, roof, windows and doors) together with its heating system and any renewable energy generation (for example solar thermal or solar PV) and calculates an energy performance score.
The energy performance score ranges from 0 to 100, with 0 being a home with the highest energy bills and 100 being a home with net zero energy bills.
The score a house achieves is reported as a letter from A to G, with A being the most energy efficient and G the least.
I created the charts below from data in the English Housing Survey 2013-14 and the Scottish House Conditions Survey 2013.
A few observations from the charts.
1. Social Housing is more energy efficient than either private-rented or owner-occupied housing.
Social housing has a much higher proportion of homes higher than D rating and homes higher than E rating. Social landlords and councils have been investing in energy efficiency for their housing stocks through a range of government incentives and obligations on energy suppliers.
2. Private-rented housing has a greater proportion of highly efficient homes than owner-occupied
Private rented housing has a higher proportion of B rated or (B+C) rated homes than owner-occupiers, but see next point.
3. Private-rented housing also has a greater proportion of very inefficient homes than owner-occupied.
Private-rented also has a higher proportion of (F+G) and (E+F+G) rated homes than owner-occupied homes. It seems like most people who own their own home take the energy performance (and perhaps comfort) of their homes to D, but no further.
4. Scotland has more energy efficient homes than England.
This is counter to what I was told in recent meetings in Scotland. There was a view that homes in Scotland were less well insulated than the rest of the UK and more expensive to heat. The EPC statistics tell a different story. However, EPCs based on SAP 2009 do not take local climate into account and assume we all live in Sheffield. If the average temperature in Scotland is lower than England then a house of the same EPC will be more expensive to heat in Scotland.
5. There's still lots to do!
There's almost no A rated homes, and very few at B. Most homes are EPC D or lower. In a previous blog I calculated that a 4kWp solar PV system will raise the EPC score of a home by 20 points - enough to jump it up one band. A solar thermal will add 3 to 6 points to a score, enough to bring many homes from one band to the next.