The best and most durable solar systems that create heat (usually to heat water) need modest amounts of electricity to drive the heat transfer pump and to power the digital controller, which ensures that heat is pumped into the system when it is needed. This means that unless you invest in an expensive array of photovoltaic panels you are still dependent upon mains electricity for your solar heat. Typically a Genersys solar system would cost about £5 per year in electricity, as well as the associated carbon costs. This still makes the system very worthwhile and very effective in reducing your carbon footprint. Solar thermal systems are the most cost effective of all renewable energy devices in saving carbon dioxide emissions. You save more carbon with your money by purchasing a solar system than with a small scale wind turbine or a heat pump or a photovoltaic array. Nevertheless the dependence on mains electricity has always concerned us at Genersys and we have been looking for a cost effective way of having our solar systems powered by renewable electricity, as well as by renewable heat.