Degree days See all Guides

Learn more about how degree days can help your organisation measure and control its energy usage in different weather conditions.

Using degree days for energy management

Four valuable uses of degree days in energy management are:

  • Constructing control charts that compare benchmarked and actual energy usage (the closer they are, the greater your energy efficiency)
  • Evaluating success of savings measures
  • Detecting faults in heating systems and their control
  • Preparing annual budgets

The Degree days for energy management (CTG075) publication (updated from CTG004) provides an introduction to degree days and shows how simple analysis can be a powerful tool in understanding weather-related energy consumption.

Degree days: technical details

The base temperature used to calculate degree days in the UK is 15.5ºC, because at this temperature most UK buildings do not need supplementary heating.

Degree days is a measure of the difference between the baseline and the actual outdoor temperature multiplied by the number of days. For example - the temperature measured hourly records a temperature of:

7.5ºC for 48 hours the degree days total would be: (15.5 - 7.5) x 2 = 16

Note - it is not possible to have a negative degree day value as when the outdoor temperature exceeds 15.5ºC no heating is needed. When the outdoor temperature does exceed the 15. 5ºC baseline, then the degree days are set to zero.

Download degree day data

The Carbon Trust no longer supplies this data, but it is freely available from:

University of Oxford Environmental Change Institute (ECI): Degree day downloads(opens in new window).

Download Degree days for energy management (CTG075)


Support for energy efficiency

If you're looking to cut energy costs and improve energy efficiency of your organisation, see our services to find out how we can help.  This includes financing and implementation support for organisations seeking to invest in energy efficient equipment.

If your organisation is based in Wales or Northern Ireland, visit our regional pages to get details of our UK government-funded support.