Tuesday, 21 January 2014

Energy savings are not just a load of hot air

The Guardian reported recently that energy saving measures at home often don't save as much as we are led to expect - at least not as much as we have been told by the Energy Saving Trust. They point out that average savings are less than half what the EST suggests for new boilers and, even worse for loft insulation*. The 'real' savings come from the NEED database which I also reported on recently (How much do you really save by insulation or a new boiler). The NEED figures are the best we have but they have their limitations. There is no need to dismiss all energy saving measures as futile - you need to look at your individual circumstances.

Firstly, the NEED report calculates savings by comparing households who have taken measures with others in a similar dwelling who have not. Unfortunately, they don't have a crystal ball and so they can't know everyone who has taken measures. This is particularly true for loft insulation which is often installed DIY. This means some of the households they assume haven't done anything actually have, so the savings are under reported.

Another complication is that even households who apparently have not installed anything (as far as NEED is aware) have nonetheless significantly reduced their energy consumption - by an average of 25% over 7 years to 2011 for some groups. This may be partly due to DIY measures but it seems certain this is also due to economy measures such as turning down the thermostat and reducing heating times. These households are sacrificing their thermal comfort in order to save money. Perhaps the ones who have a new boiler or insulation don't feel the need to do this. This effect also leads to under-reporting of savings.

Energy savings are typically estimated on the basis that you don't heat your home more than you did before but in practice you usually do. Even if you don't change the controls at all you will find that you are warmer than before because:
  • You don't cool down as quickly as you did when the heating goes off
  • Your heating system is able to keep you warm when previously it didn't. (Before our retrofit our old system simply wasn't up to it. On cold days even working flat out we were freezing, see A retroft experience: the savings.
If you want to get the full savings from your retrofit you will need to adjust your heating controls. For example you might turn the heating off earlier before you go to bed, because your house will stay warm for longer.

For most people, energy saving retrofit will make some savings on their bill and also make them more comfortable. If you have been economising hard on heating then you won't save much money because you can't save what you aren't spending. When you get a Green Deal assessment for your home they estimate savings for your particular case taking into account your current heating regime and bills. I have friends who were dismayed at how little they were told solid wall insulation would save for them but this is because they are very stingy with their heating - and they are unlikely to get a grant for it either because the carbon savings will be low for the same reason. (Were they on benefits they might get a grant anyway.)

In summary, if financial savings is your only motivation for installing insulation or a new boiler then you must get a personal assessment, not rely on average figures. If you are stingy with your heating now then your savings will be disappointing. If comfort is worth something to you too then you must take that into account.


*The EST say in their defence that they compute savings based on no previous loft insulation [2]. However more than 90% of homes have at least 50mm already, and the first 50mm cuts heat loss by two thirds), so their figure for savings is irrelevant for most people.

[1] The energy efficiency 'savings' that are just hot air (Guardian) 18/Jan/2014
[2] Our Calculations (Energy Saving Trust)

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