 David Toke et al (Letters, 27 December) argues for feed-in tariffs for renewable energy, as opposed to technologically neutral support for low-carbon electricity generation. The weather over the last month (intense cold and negligible wind) has shown that dependence on renewables alone is unlikely to replace our existing generation capacity, let alone provide the power needed to replace burning of fossil fuels for domestic heating, as proposed by Chris Huhne. Polls may show "that the public wants payments to be reserved for renewable energy, not nuclear", but their first priority is likely to be that they have the energy to heat and light their homes.  The challenge is that to ensure sufficient power for conditions like those seen recently, we will have excess low-carbon generation capacity in the summer. a feed-in tariff when there is not a continuous demand is unlikely to be a suitable solution. The government is to be congratulated on starting to address the complex problems of how to decarbonise our energy use. To meet the objectives of the Climate Change act, we will need both renewables and nuclear and we need to start construction, rather than continuing to debate the options.  Professor Roger Kemp  Lancaster University