Your building’s energy use will depend on the weather outside – if it is cold then the boiler will need to work harder (use more energy) to heat the building. This means that monthly and weekly energy consumptions can vary along with the weather.

To accurately compare energy consumption from one year to the next, Pilio needs to account for the effect the weather has on the data. Heating Degree Days is a measure of how cold it has been, and therefore what demand your building has for heating to maintain a desired comfort level. When Pilio “weather-corrects” the energy consumption, it simply divides total heating energy consumption by the total number of Heating Degree Days for the year. The result is kWh/degree days.

Next, Pilio multiplies this result by the average number of degree days for a year. It is then possible to compare energy performance year to year – if performance is the same with this weather correction then the result between 2 years should be equal.

Once the weather has been corrected for it is much easier to see if your energy use is changing year-to-year. For example, whilst the raw energy consumption might indicate that you are using more and more energy this winter than last, the weather-corrected energy consumption could show that, actually, this is just because this winter is colder than last year. This approach to weather-correction can be done for a week or a month if the average number of degree days is known.

Weather correction is essential for:

1) Assessing accurately if your efficiency measures are really working.

2) Measuring accurately if progress on an energy or carbon reduction goal is genuinely being achieved.

3) Anticipating energy costs.