Two of the world’s biggest sources of carbon dioxide emissions are generating electrical energy and heating our buildings. But as generating electricity from fossil fuels involves generating heat at the same time, should they not be put together?

Combined heat-and-power (CHP, also known as co-generation) plants are hardly new – in Scandinavia, they have been commonplace for decades. Nearly all of Copenhagen is connected up to communal heating systems based on CHP, for instance.