if u cant afford to buy it dont have it , when these companies fit it for free the difference to your bill will be very small as they use the feeding tariff of approx 43p per kw produced by the panels and any rhi grant as proffit.all the householder will sava is approx 12p per kw provided they use it when it is produced.there are other problems in these contracts, if u would like more info pm me a number before u go ahead ?