This article describes a Japanese heat pump to heat water, which reduces gas consumption by 30% compared to a natural gas fired heater. That's pretty good. It might find a market in urban areas or for large buildings, which is what the prototype in the article appears to show. However, for most water heating applications in Japan I think they should stick to roof-mounted solar heaters. In that climate they are incredibly effective most of the year. They are also very cheap.
They should use these in Florida, as well. I think I read that in Australia they are now mandatory for new construction. Of course you could use both, but I doubt that any heat pump could increase the temperature of water from a solar heater in Japan for 9 months of the year. I think it makes more sense to use conventional gas heating as an auxiliary heater when solar does not work well, on rainy days or in winter. This is how most people I know do it. Also, most people use the heater exclusively for the bath, or the bath and washing machine, and they use a hot-water-on-demand instant heater in the kitchen. Most domestic hot water consumption in Japan is for the bath. On recent trips to Japan and photos on the news, I have been struck by the large number of houses and buildings with PV electric panels on the roof, especially in southern Japan, which is the only place I ever go. The price of PV panels has apparently fallen drastically, and they are spreading rapidly. Electric power is expensive in Japan. The climate in southern Japan is like Florida's, and sunny most of the time. PV and solar water heater policies and gov't support that works there may not apply to Iowa or New York. - Jed
