The increasing prevalence of renewable and intermittent energy sources in the electricity system is creating new challenges for the interaction of the system. In Denmark, high renewable shares have been achieved without great difficulty, mainly due to the flexibility of the nearby Nordic hydro-power dominated system. Further increases in the share of renewable energy sources require that additional options are considered to facilitate integration with the lowest possible cost. With large shares of intermittent energy, the impact can be observed on wholesale prices, giving both lower prices and higher volatility. A lack of wind that causes high prices is rarely seen because long periods without wind are uncommon. Therefore we focus on the low price effects and the increased value of flexible demand options. On the supply side, there is an increase in the value of other flexible generation technologies and the attractiveness of additional interconnection capacity. This paper also analyses options for increasing the flexibility of heat generation involving large and decentralized CHP plants and heat generation based on electricity. The incentives that the market provides for shifting demand and using electricity for heat production are discussed based on the variability of prices observed from 2006 to 2008. (C) 2010 Elsevier Ltd. All rights reserved.