Since water heating accounts for between 30% and 50% of the electric power expense for the typical residence, it's wise to think about ways to decrease this particular expense. The hot water in most homes is stored in a geyser, with an electric resistance element which usually consumes between 3kW and 4kW of electrical energy.

Two systems are generally used to assume the task of providing hot water. Solar Water Heating (SWH), which uses solar collectors or solar panels typically installed on the roof of the building, is a well-proven technology in which radiant warmth from the sun is employed to directly heat the water. Heat pumps are electrically-driven devices which transform the background air temperature into heat, commonly employing around 1/3 of the electrical power of an equivalent resistance element.

There are numerous aspects which impact the choice between a solar water heating system and a heat pump system for domestic water heating. Here are a few of the benefits and drawbacks of each kind of installation.

Solar Water Heating: Pros

1. SWH is a well-established technology
2. SWH systems are capable of delivering very high water temperatures
3. ESKOM subsidises SWH systems (terms and conditions apply)
4. SWH systems ordinarily provide a reduction of around 15% on your electricity costs.

Solar Water Heating: Cons

1. You may find big solar panels on your roof unattractive. On the flip side, they do act as an advertisement of your green qualifications!
2. Solar water heating installations are less efficient when it's rainy or cloudy, and don't work during the night. This results in the water temperature fluctuating depending on the weather. A back-up electric heating element ordinarily takes care of this problem, but when it is functioning, you are no longer saving electrical energy.
3. The collector panels need to be oriented correctly in order to acquire as much solar radiation as possible.
4. Water filled solar panels are heavy. Your roof may need structural reinforcement before you can place solar collectors on it.
5. SWH installations will usually have a greater up-front cost compared to a comparable heat pump system.
6. The payback period of 6-8 years is usually longer compared to that of a heat pump installation.
7. The glass components are vunerable to damage from freezing, over-pressurization and getting struck by hard objects.
8. The temperature created in solar panels can't easily be regulated. Electrical geysers aren't designed to stand up to the pressure that can build up when water is heated by the sun. If you don't replace your hot water cylinder with one designed for solar heating, there is a real risk of the hot water tank bursting in the roof.

Heat pumps: Pros

1. The up-front expenditures are generally less than those of an equivalent SWH installation.
2. The payback period of 2-4 years is generally shorter than the payback period for a SWH installation.
3. Heat pumps operate day and night, rain and shine. Note that the heat pump only operates when it is necessary to renew the hot water in the geyser.
4. Heat pumps typically offer a reduction in water heating cost of at least 67%. Considering water heating commonly is the reason for 30% - 50% of your electricity cost, this amounts to a saving of between 20% and 33% on your electricity costs.
5. Heat pumps are easier to install (and to retro-fit to an existing geyser.) Nevertheless, the services of a manufacturer-certified installer are required for guarantee and insurance purposes.
6. Heat pump installations usually operate at a lower pressure than solar water heating systems. This cuts down the risk of geysers bursting. It also signifies that a heat pump can safely be retrofitted to an existing electrical hot water tank system.
7. Modern day heat pump installations provide you with a remote control panel which permits you to set the water temperature without crawling around in the roof.
8. Heat pumps are generally mechanically simple and dependable.

Heat pumps: Cons

1. Heat pumps become less efficient as the air temperature drops below freezing.
2. The maximum water temperature is around 65 degrees. Since any temperature above 52 degrees carries the risk of scalding, this should be ample for most domestic purposes.
3. A heat pump makes use of a fan, which usually tends to make a small amount of noise. This ought to be taken into account when the location of the device is selected.
4. Heat pumps don't function without electrical power, eg. during electricity outages. On the other hand, a small device draws less power than a kettle, and may very easily be run off-grid by a solar electric or wind turbine system.
5. Heat pumps, like air conditioners and refrigerators, may use greenhouse gases.

Although heat pumps were first described in 1852 by Lord Kelvin, they have been slow to gain acceptance in South Africa. ESKOM currently offers a subsidy for commercial heat pump installations, but they do not give a subsidy for household systems. Nevertheless, the fitted cost of a heat pump installation is usually less than the installed cost of a subsidised solar water heating system.