My son and I have been discussing how to reduce the household carbon footprint. We don't use the car much (we use bikes a lot) and I plan to get a hybrid or electric one next, depending on now the charging network develops in Brittany (we take the car over a couple of times a year) and the London area where we live, over the next 1-2years. However the gas central heating and not water system is the biggest carbon emitter. The house is big and old (Victorian, so leaky, heatwise). The least intrusive and expensive option seems to be an air-to-water heat pump. Ideally I want a system that can slot in, in place of the gas boiler we have now, and can still provide hot water at 70-80C , sufficient to heat the house and the water cylinder, using the existing pipework and radiators. It seems Daikin are offering a 2-stage heat pump that does this, which seems like an excellent idea if the UK is going to wean itself comparatively inexpensively and quickly off its current North Sea Gas habit. It could be just what I'm looking for. But I have not seen any other supplier that offers this. Does anyone have experience of this type of system, or any tips regarding possible pitfalls? Also, is the technology mature enough yet, or is it better to give it a couple more years before investing?