The domestic sector uses nearly 30% of the total energy used in the UK, and 80% of that is used for space and water heating.
Reducing energy use in this sector would clearly help reduce emissions and help the UK move towards its carbon targets.
Several approaches have been used to do this – from carrying out performance measurements using the Standard Assessment Procedure (SAP) and providing Energy Performance Certificates (EPCs) to dispensing written and face to face advice and information on how to save energy.
There are very few studies on whether any of these approaches actually result in savings.
A study published by the Behavioural Insights Team (BIT) in late 2017commissioned by NEST and Npower found that the predicted results from models such as the SAP varied widely from actual performance.
For example, the SAP predicted that savings from loft insulation in a medium home would be £120 and pay back in 2.5 years.
Real world data had a saving of £21, raising the payback period to 11 years.
On a day to day basis, however, the way in which people use the controls and settings in their homes has a greater impact on the amount of energy they use.
Does providing advice improve how they use their controls?
Another study in 2014 found that written information or advice in the home had no impact in the amount of energy used.
In some cases, showing people how to use their thermostats may have increased energy usage as they now used them to increase temperatures and get more comfortable.
This could be because of a number of reasons, and include the common problems with behaviour such as forgetting, ingrained habits and just not wanting to deal with the effort or hassle or doing something.
The purpose of the NEST and Npower commissioned study was to see if there was a statistically significant saving to be had from using a system like the NEST learning thermostat, which uses sensors and machine learning to optimise the heating schedule.
Once installed, NEST uses occupancy and weather data that is collected over time to figure out when it should turn the heating up to ensure comfort levels are maintained and when it can be reduced without impact.
Four studies – the most rigorous of their kind so far – showed that compared to homes having a programmable timer, thermostat and radiator valves, the NEST system could save 4.5 – 5% of total gas consumption.
Adding in an optional feature that does seasonal savings by tweaking winter use adds another 3.3% to the savings figure, taking the total to nearly 8%.
It can also nudge users – giving them leaves if they turn down the heating and act in an energy efficient way.
The thermostat is around £280 installed, with a payback of 6.5 to 11 years.
And this is still where the problem lies.
Even at a relatively low capital cost, the payback is going to be on the order of 10 years.
And that makes it hard to create a simple business case for change – especially for operators of large portfolios that may quickly have to spend hundreds of thousands of pounds to retrofit a few thousand homes.
New homes will probably get systems like NEST fitted as standard and, when we do a major refurb, it will be a small part of the overall cost and easy to justify.
But, in summary, the evidence shows that we get better results when we automate how choices are made rather than if we ask people to change.