What is Weather normalization?
Weather normalization adjusts energy or water use for differences in weather, usually with heating and cooling degree days, so that periods and sites can be compared on equal terms.
Where normalized figures are used
Benchmarking programs, building performance standards, measurement and verification, utility budgets and portfolio rankings all rely on it. Without it, a mild year looks like an efficiency gain and a hot one hides real progress.
How degree days are counted
Per the US EIA, degree days compare a day's mean outdoor temperature with a base of 65 degrees Fahrenheit: a day with a high of 90 and a low of 66 averages 78, which gives 13 cooling degree days. ENERGY STAR Portfolio Manager uses the same 65 degree base and defines weather-normalized energy as the energy a building would have used under average climate conditions, using temperature data published by NOAA's National Centers for Environmental Information.
How Aqueduct fits the baseline
Aqueduct fits a regression of each site's usage on cooling and heating degree days, pulling historical weather for the site's location over the baseline window and live weather afterward. The window runs up to 12 months with a 6 month minimum, and uploaded utility bills let a new site start on day one. Results read as above or below expected, rate configuration converts the gap to money, and the same method runs for water, electricity and gas.