The effect of clock changes on energy consumption in UK buildings

The report looks at the impact of changing UK clocks from GMT to British Summer Time on energy use, compared to adopting Central European Time (CET).

The issue of clock changes has been raised as a potential way of reducing carbon emissions. An earlier study concentrated on modelling the expected impact of the clock change on the likelihood of artificial lighting being switched off in response to daylight availability. The work presented here expands on this earlier work and looks at the impact of clock change on energy use for lighting, heating and cooling using dynamic simulation modelling to capture the interactions between the energy services. This report was prepared for the Department for Environment, Food and Rural Affairs (DEFRA) and published by BRE in 2005.

Key findings

It is unlikely that the a switch to either Central European Time (BBST/DBST), or BST all year round (BST/BST) would lead to significant CO₂ savings.
Both clock change regimes would result in an increase in energy consumption in UK buildings, rather than realise any savings.
Overall the changes result in only a small difference to energy for heating, lighting and cooling in UK buildings and were similar for 2010 and 2020.
The only instances where savings are realised are for domestic lighting and non-domestic cooling for the switch to Central European Time, but these would be outweighed by other effects.

Report summary

Simulations were used to determine the impact of a clock change on annual energy consumption for heating, and in the case of non-domestic buildings for lighting and cooling as well.

The modelling results were scaled to the UK level for 2010 and 2020 based the projected energy consumption for the reference scenarios developed for the domestic and non-domestic sectors.

The result of this study indicate that both clock change regimes would result in an increase in energy consumption in UK buildings, rather than realise any savings. Overall the changes result in only a small difference to energy for heating, lighting and cooling in UK buildings and were similar for 2010 and 2020. The switch to Central European Time (BBST/DBST) showing 2% increase in both delivered energy use and CO₂ emissions (around 40 PJ and 2.5 M Tonnes CO₂, respectively). Whilst a switch to BST all year round (BST/BST) would result in a smaller increase of just under 1% (around 20 PJ and 3 5 M Tonnes CO₂, respectively).

The only instances where savings are realised are for domestic lighting and non-domestic cooling for the switch to Central European Time. However, these savings are more than offset by the increases in non-domestic heating and lighting, as well as a small increase in domestic heating.

As these results are based on a limited number of simulations, there is uncertainty associated with the final figures. However, it is unlikely that the a switch to either Central European Time (BBST/DBST), or BST all year round (BST/BST) would lead to significant CO₂ savings.