an efficiency benefit associated with CHP. Appropriate measurement of the efficiency benefit of CHP requires a comparison of the costs of CHP generation with that of the separate centralised generation of (power station) electricity and (gas boiler) heat. However, since heat is not explicitly modelled in WADE, this is not possible. In order to capture the efficiency benefit of CHP in the WADE model, the input electrical efficiency data is increased as an approximation for the heat benefit associated with CHP, taking account of different sizes of CHP plant and their associated efficiencies. This is an important limitation of the WADE model (and is explicitly recognised by the modellers): CHP is likely to play a crucial role in a future DG scenario (in this case the modellers assume over 50% of new capacity is accounted for by CHP technologies), so the simplified treatment of CHP may well have important implications for model results.