When it started it was basically a question of the local environment and the price of fossil fuel oil. We were caught in oil dependence. We found it was very high in heated buildings--way beyond 8%. When the prices rose, it was a problem for the economy, for single families, and so on.
The two basic reasons were oil dependence and the regional environment. At that time we were talking about sulphur dioxide and nitrogen oxides. There was a plan to make more efficient and fuel-efficient systems and convert those systems.
In Sweden, 50% of all energy comes from hydro power; it used to be nuclear power. I'm not sure of the figure, but today about 50% comes from cogeneration. The district heating system is a source of electricity production that is more efficient than just power plants, because the waste heat is used for heating buildings.
So the reasons were more efficient electricity production, oil dependence, and environmental aspects.