The nuclear versus renewables debate is getting hotter. In my view, most of the opinions I have heard are mistaken and do not understand the key energy issues. Most are approaching it from the angle that we must produce enough energy to meet growing demand. This is not sensible, since we have become very wasteful because energy has been cheap and plentiful.

On the whole, without fossil fuels, saving energy is generally much cheaper and more effective than generating it. In the future, energy is going to be scarce and expensive whether we like it or not. Our best chance of managing climate change is to put all our efforts into using energy carefully.

Some commentators seem to confuse electricity with energy. Electricity is a small part of our energy use. In this country most of the energy we use is for heating, and for this we mostly burn gas or oil. Another major use is transport. We could use electricity for heating and to make hydrogen fuel for transport, but this only makes sense if we can easily generate plenty of electricity. In reality, electricity is difficult to generate without fossil fuels, so to waste it on heating and transport makes no sense.

Electricity generation in fossil fuel or nuclear power stations is only about 30% efficient. Indeed the electricity industry is the main UK consumer of energy, because it consumes about three times what it generates. The other 70% of the heat is wasted and goes up the chimney and cooling tower or warms a nearby river. Physics says that it is very difficult to do better than that. So to use electricity for heating is very wasteful.

Nuclear and most renewables generate electricity. The scale of our energy use means we cannot build enough of either in the short or medium term to satisfy all our growing demand. To replace all fossil fuels with nuclear in the UK would need about 400 nuclear power stations, at a cost of about £1 billion each. There is not enough nuclear fuel left to power this many reactors. To do this for the whole world at UK living standards would need tens of thousands of nuclear stations. Similarly, to generate this much electricity with wind turbines would need about as many windmills as we have trees. In the long term, trying to replace fossil fuels with nuclear or renewables would mean most of the world economy focussed on generating electricity. So neither nuclear nor renewables is the whole answer.

Another possible idea is to grow oils as fuel for transport. Again the scale is the problem. To replace fossil fuels for existing transport would mean covering the countryside with oil-seed rape. On a world scale this would not leave enough land to feed us.

So the sensible strategy would be to focus on using energy much more effectively. The biggest waster of energy is the electricity generation industry, which sends two thirds of its energy up the cooling tower as waste heat. If we could use all this heat for space heating it would make a real difference. This idea is called Combined Heat and Power (CHP).

CHP is old technology that has never been taken seriously because it doesn't fit with the way electricity generation is structured. Big power stations are not good neighbours, and need to be sited away from where heat is needed. So we need smaller more local power stations in towns and cities, selling heat as well as electricity. Or go even smaller and combine generating electricity with your central heating boiler. This technology is now available and could be more important than wind power.

The average house is still very badly insulated, with poor heating controls. Workplaces, shops and schools are even worse. We need more help and grants to insulate existing buildings, and higher standards for new buildings. We can reduce energy demand further by wearing warmer clothes and turning down the thermostat. Flats are more energy efficient than detached houses. Good design, such as putting most windows in a south facing wall, can make a real difference at almost no extra cost for a new building. The best designs are so well insulated they need almost no heating.

Efficient appliances such as fridges and tumble dyers are available, but are often more expensive. We could have more tax on wasteful appliances to pay for subsidies on efficient ones.

Big savings can also be made in transport. Most lorry journeys are unnecessary, and only happen because it is cheaper to move goods than to sell them locally. Cheap fuel means it is cheaper to drive food and goods hundreds of miles to a central warehouse and back rather than use local food and goods. It is cheaper to fly and ship food from the other side of the world than to grow it here.

So the argument between nuclear and renewables is almost a side issue. We are rapidly coming to the end of the era of cheap plentiful fuel, and neither nuclear nor renewables will change that. The change to the new era will be painful, and the longer we try to put it off the more painful it will be. The more efficiently we use energy the easier it will be.

Alan