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Temperature Adjustment of UK Energy Statistics. Iain MacLeay. Between 2009 and 2010 what happened to UK energy consumption ? Did it Rise by 3.9% Rise by 2.9% Remain broadly unchanged Fall by 0.6%. Annual average temperature (degrees Celsius). Statistical Model.
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Temperature Adjustment of UK Energy Statistics Iain MacLeay
Between 2009 and 2010 what happened to UK energy consumption ? Did it • Rise by 3.9% • Rise by 2.9% • Remain broadly unchanged • Fall by 0.6%
Statistical Model Y = C * I * S * TD * E * temp Where: Y = observed time series C = trend-cycle I = irregular component S = seasonal factor TD = trading day effect E = Easter effect temp = Temperature coefficient Note: Model can be arithmetic rather than multiplicative Y = C + I + S + TD + E + temp; or a combination of the two.
Temperature correction Y / temp = C * I *S * TD * E Assume no temperature, Easter or trading day effects then: Y = C * I * S And the seasonally and temperature adjusted series is Y / S = C * I
Two main statistical techniques used • Regression • Easter • Trading days • Temperature effects • Moving averages • Trend-cycle • Seasonal component + ARIMA modelling to help improve the calculation of the moving averages (extend time series by forecasting one year of additional data)
How do we currently adjust for temperature • Gas • National Grid provide temperature adjusted series as well as the raw data for gas • Adjustments are smaller in the summer months of July and August. Largest adjustments in fact appear in Spring and Autumn • Does this seem sensible ? • Coal • Adjusted by factor of 2.1. • If temperature is 2 degrees above “normal” then factor = (2 * 2.1) = 4.2. Raw data is divided by 0.958 resulting in temperature adjustment increasing the series. • Warm weather – use less energy – so temperature adjusted series should be higher • Same adjustment used irrespective of season
Temperature adjustment Alternative methods • Use same factors for each month – or specific factors for each month • Use monthly average temperatures (current practice) or degree days (only use heating if daily temperature above/below threshold) 3. Growth in cooling – should this be adjusted for? Data • DECC receive data from the Met Office (17 stations reporting daily max and min temperatures)
