Heat pumps lift heat from a low-temperature sources(ground, water or air), to useful temperatures. They are used for space and water heating, cooling, and refrigeration.Recently heat pump water heater and heat pump washing and drying machine are popular in Japanese residential use. Even in winter, the ambient air still contain heat which can be extracted by heat pump, so the air conditioner can warm up the room by pumping up heat.

Most heat pumps are driven by an electric energy. The needed energy is only about one third or less of the useful heat production, so they are excellentenergy conservation system. In addition, heat pumps contribute much to the reduction of carbon dioxide emissions, because the CO₂ intensity of the grid is low.

In EU and Japan heat pumps are handled as renewable energy. EU is planning to increase the share of renewable energy to 20% by 2020.

< Heat pump technologies in home electric appliances >

CRIEPI focused on the hot water supply energy which accounts for 30% of the final energy consumption in residential sector.
Combustion type water heater have a majority market share, so the development and spread of high efficient heat pump water heater are expected to contribute energy conservation.

< Hot water supply energy supply-demand structure in residential part >