we have an air-heat pump for over a year and it has saved us money, even with continuous use.
Yesterday we installed Photovoltic cells and today with an overcast sky we have generated 500watts wow. We hope to make all our electricity use for about 4 months in the summer.
The firm that installed our cells. is Joju and I would strongly recommend them. The work force are charming, clean and will alter things even if it has taken them an hour to set a up a sytem. The comany itself keeps you the client informed and communication is excellent. Interesting fact, when we enquired about installing cells, they said they would phone back, uhh. 10mins later they had done the survey, even to measuring the roof and the amount of exposure to the sun all with Google Earth.