Definition

• Heat pumps and solar hot water heaters are both used to save energy in homes that heat water for household activities such as showers and dishwashing. Heat pumps use a heat transference system, usually with some type of refrigerant gas that allows heat to be moved into the heat pump system from the air, the ground, or water leaving the house from showers, dishwashers, or other appliances that pump heated water. A certain amount of electricity is used to enhance the heat even more with the help of heating elements.
  
  Solar water heaters, on the other hand, gather in the sun's heat from panels installed on the roof. These panels are especially designed to pick up solar radiation, absorbing as much heat as possible, and then transfer it as electricity or heat to a heating system. Heating elements may also be used to additionally heat water to the necessary temperature or in off-hours.
  
  

Energy Savings

• Both systems are rated highly for energy savings, which is measured in megawatts. Solar water heaters generally save more energy than heat pumps, around 33 to 47 mw, while heat pumps only save about 30 mw. However, the savings from heat pumps are almost always consistent, while solar water heaters depend largely on sunlight hours throughout the year so that savings can vary considerably.
  
  

Cost

• Costs for putting in either system vary with the size and quality of the necessary devices. Solar water heaters are made of fairly simple materials without many moving parts, so their costs tend to be slightly lower than those of heating pumps. However, installation costs are slightly higher, because a solar water heater needs to be installed in multiple locations throughout the house and often requires renovation. So although $1,500 is an average price for both systems, other factors also play a part in deciding overall costs. In general, a solar water heater will also be slightly faster in "paying back" the cost through energy savings.
  
  

Size

• Both solar water heaters and heat pumps take up about a square yard of space in either the basement or the yard. Unfortunately, the solar water heater also takes up a large amount of roof space, which usually needs to face as much sun as possible.
  
  

Considerations

• While solar water heaters need sunlight, heat pumps depend on gases to transfer heat and may suffer leaks that need to be repair. There may also be taxes and rebates that apply to either solar water heaters or heat pumps, and they may differ from state to state or country to country.