Using published bid/ask curves to error dress spot electricity price forecasts

Abstract

Accurate forecasts of electricity spot prices are essential to the daily operational and planning decisions made by power producers and distributors. Typically, point forecasts of these quantities suffice, particularly in the Nord Pool market where the large quantity of hydro power leads to price stability. However, when situations become irregular, deviations on the price scale can often be extreme and difficult to pinpoint precisely, which is a result of the highly varying marginal costs of generating facilities at the edges of the load curve. In these situations it is useful to supplant a point forecast of price with a distributional forecast, in particular one whose tails are adaptive to the current production regime. This work outlines a methodology for leveraging published bid/ask information from the Nord Pool market to construct such adaptive predictive distributions. Our methodology is a non-standard application of the concept of error-dressing, which couples a feature driven error distribution in volume space with a non-linear transformation via the published bid/ask curves to obtain highly non-symmetric, adaptive price distributions. Using data from the Nord Pool market, we show that our method outperforms more standard forms of distributional modeling. We further show how such distributions can be used to render `warning systems' that issue reliable probabilities of prices exceeding various important thresholds.