In this paper we develop a general framework for valuation and hedging electricity derivatives. We propose a multi-factor forward curve model consistent with market prices. The electricity forward price is modelled as arithmetic Brownian motion. The main advantage of our model compared to the geometric Brownian forward curve models suggested previously in the literature is that closed form solution to average based derivatives can be easily computed. This is important in the electricity industry, since most contingent claims in this market are derived from (arithmetic) price averages. The dynamic properties of two different average based forward contracts are investigated. Furthermore, closed form solutions to both European and Asian options and corresponding hedge ratios are calculated. Finally we implement the model and provide some numerical examples using data from the Nordic electricity market.