Heat Pump Or Solar Panels

A typical heatpump for domestic use
A typical heatpump for domestic use

Since water heating accounts for somewhere between 30% and 50% of the electrical power cost for the average home, it makes sense to check out methods to cut down this cost. The hot water for most residences is stored in a hot water cylinder, with an electric resistance element which utilizes somewhere between 3kW and 4kW of electrical power.
Two systems are generally employed to assume the job of supplying hot water. Solar Water Heating (SWH), which utilizes solar collectors or solar panels typically installed on the roof of the building, is a well-proven technology in which radiant heat from the sun is used to directly heat the water. Heat pumps are electrically-driven units which convert the background air temperature into heat, generally using around 1/3 of the electric power of an equivalent heating element.
There are a number of variables which impact the choice between a solar water heating system and a heat pump installation for domestic water heating. Here are a few of the benefits and drawbacks of each type of set up.
Solar Water Heating: Pros
1. SWH is a well-established technology
2. SWH installations are capable of providing high water temperatures
3. ESKOM subsidises SWH systems (terms and conditions apply)
4. SWH installations ordinarily give you a saving of about 15% on your electricity bill.
Solar Water Heating: Cons
1. You might find large solar panels on your roof unappealing. On the flip side, they do act as an advertisement of your environmentally friendly credentials!
2. Solar water heating installations are less efficient when it’s wet or cloudy, and don’t function at night. This leads to the water temperature fluctuating depending on the weather. A backup electric heating element generally takes care of this problem, but while it is working, you are no longer conserving electricity.
3. The collector panels must be oriented the right way in order to collect as much solar radiation as possible.
4. Water filled panels are usually heavy. Your roof may need structural reinforcement before you can place solar collectors on it.
5. SWH systems will usually have a greater up-front expense than a comparable heat pump system.
6. The investment recovery period of 6-8 years is generally lengthier than that of a heat pump installation.
7. The glass parts are susceptible to damage from freezing, over-pressurization and getting struck by hard physical objects.
8. The heat created within solar panels can’t easily be regulated. Electric hot water cylinders aren’t built to stand up to the pressure that may build up when water is heated by the sun. If you don’t replace your geyser with one created for solar heating, there is a real danger of the hot water cylinder exploding in the roof.
Heat pumps: Pros
1. The up-front costs are usually lower than those of a comparable SWH installation.
2. The investment recovery period of 2-4 years is normally shorter than the payback period for a SWH system.
3. Heat pumps function night and day, rain and shine. Note that the heat pump only operates when it is necessary to replenish the hot water in the hot water cylinder.
4. Heat pumps typically provide a saving in water heating cost of at least 67%. Since water heating generally is the reason for 30% – 50% of your electric power cost, this amounts to a saving of between 20% and 33% on your electricity bill.
5. Heat pumps are less complicated to put in (and to retro-fit to an existing hot water cylinder.) Nevertheless, the skills of a manufacturer-certified installer are required for warranty and insurance cover purposes.
6. Heat pump systems usually function at a lower pressure than solar water heating systems. This decreases the risk of geysers bursting. It also means that a heat pump can safely be retrofitted to an existing electric hot water tank system.
7. Contemporary heat pump systems provide you with a remote control panel which permits you to set the water temperatures without crawling around in the roof.
8. Heat pumps are mechanically uncomplicated and reliable.
Heat pumps: Cons
1. Heat pumps become less economical 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 adequate for most household uses.
3. A heat pump utilizes a fan, which tends to make a small amount of noise. This ought to be taken into consideration when the location of the unit is selected.
4. Heat pumps don’t function with no electrical energy, eg. during electricity outages. Nevertheless, a smaller device draws less electrical power than a kettle, and can 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 at this time offers a subsidy for commercial heat pump installations, but they do not offer a subsidy for residential systems. However, the installed price of a heat pump system is usually less than the installed cost of a subsidised solar water heating system.
Heat Sense supplies and installs heat pump systems in Johannesburg, South Africa. You can find out more about how to save energy and money at our website,

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