This paper proposes a novel indirect-expansion solar-assisted multifunctional heat pump (IX-SAMHP) which integrates a domestic heat pump with a solar water heater. The IX-SAMHP can not only work in operation modes included in the two household appliances, but also operate in four new energy-saving operation modes for the space cooling, space heating and water heating. All operation modes have functioned successfully and can be switched to each other smoothly on a purpose-built experimental setup. Experiments of the heat pump water heating mode at outdoor air temperatures of 8 degrees C and 15 degrees C and the solar-assisted space heating mode at indoor air temperatures of 20 degrees C have been investigated in detail. Electric heaters were used to simulate solar radiation intensity in different weather conditions. The experimental results show that the IX-SAMHP can produce hot water with much less electric consumption in cloudy days compared with a solar water heater and can operate in much higher coefficient of performance than a domestic heat pump in cold winter. The IX-SAMHP is especially suitable for the regions abundant in solar radiation where the space heating, space cooling and water heating are required all the year round. (C) 2010 Elsevier B.V. All rights reserved.