I don't want to put anyone off doing the right thing by the planet, but I'd like to offer a cautionary word. DH was in a related industry and a friend needed a business opportunity. Having been asked frequently about AC, he suggested that, and then heat pump technology kicked off. You aren't interested in the bits in between, but we have had a small air source heat pump/AC in our kitchen for about twelve years (12 years)... and we are about to replace it... for the fourth (X4) time. The original idea was awesome, the technology works well, but the components are so badly and cheaply made in China (down to a price) that anything anyone tells you should be taken with a kilo of salt. So the energy costs might look good, but the components are sh1te. We need a new controller board, at £700 + VAT (5 weeks delivery) or a whole new system at £1150 +VAT (in stock). With one, we get a two year guarantee.. So do, please consider whether you want to save your electricity bill or stump up £1200 every three years, while paying your electricity.