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July 2017

Heat Pumps vs. Solar Water Heaters

By | Energy Partners Knowledge Base | No Comments

Which is best for energy-efficient water heating?

Warm water from the tap is a modern-day luxury we have come to rely on every day, but do you know how much it is costing you? If you are heating water using a conventional electric geyser, it is making a significant dent in your monthly budget. In fact, in most regular households with more than two family members, the geyser is the heaviest electricity user and can account for as much as 50% of the electricity bill.

Therefore, one of the first steps in cutting your electricity bill is replacing your regular electric geyser with an energy-efficient alternative. Heat pumps and solar water heaters are two of the best options out there and both make great energy-savvy investments. But what is the difference between them and which one is best for you? Understanding how they work and weighing up their pros and cons can help you make the right choice for your home.

 

Heat Pump

 

Heat Pump

A heat pump uses energy from the surrounding air to heat water.

How it works

Absorbs energy from the surrounding air and transfers the heat to the water (the reverse of how an air con works).

Energy use and expected savings

The energy use is only slightly affected by variations in temperature, and therefore it runs efficiently at any time of day. Requires approximately one-third of the energy of a conventional geyser to heat the same amount of water. This leads to savings of up to 70% on heating water.

Maintenance

Requires general service every 18 to 24 months.

Life expectancy

Expected to last for 5-10 years.

 

Solar Water Heater

 

Solar Water Heater

A solar water heater relies on the sun for power.

How it works

Uses energy from the sun to heat water.

Energy use and expected savings

When there is direct sunlight on the panel, no grid electricity is used. When there is no solar energy available, such as at night, this system relies on a regular geyser element to heat your water to the desired temperature. Therefore the total savings vary a lot, depending on the orientation of the panel and when you use your hot water. Typically you can expect savings of up to 45%-70% on water heating.

Maintenance

Should be inspected and serviced every 18-24 months.

Life expectancy

Expected to last for 10 years or more.

 

While it is more expensive to install a heat pump than a solar water heater, a heat pump could save you more money on electricity, which will ultimately foot the bill of the initial installation.The table and graph below weigh up the electricity savings you could expect when installing a heat pump versus a solar water heater:

 

Solar water heater and 200L tank (20 evacuated tubes) Heat pump and 300L efficient tank (3.4 kW)
Initial capital investment (incl. VAT) includes: all components and installation R 26 391 R 35 495
Estimated payback period 3.83 years 4.43 years
Savings in the first year (incl. VAT) R 6 228 R 7 326
Savings % (water heating only) 54% 70%
10-year cumulative savings R 59 660 R 62 553

Note: The figures are based on City of Cape Town tariffs and a standard household with 4 family members using an average of 52 L of warm water per person per day during summer and 85 L of warm water per person per day during winter.

 

Cumulative Savings

The graph compares how much a solar water heater and a heat pump could save a homeowner over the course of 10 years. Light Blue: Heat Pump. Dark Blue: Solar Water Heater.

Cala van der Westhuizen from Energy Partners Home Solutions says in most cases they recommend heat pumps in the Western Cape for the following reasons:

  1. It is more efficient than an electric geyser and leads to bigger electricity savings over the long term than a solar water heater.
  2. The region receives a lot less sunlight during the winter months, which means a solar geyser will use a lot more electricity to keep the water hot.  
  3. Coupling a large, highly insulated water tank with a heat pump works very well when combined with a Solar PV systemto increase your savings. How it works is that solar energy is simply absorbed and stored as heat in the tank for later use.

Van der Westhuizen concludes: “In the Western Cape, where there is not enough solar energy during the winter, heat pumps are our recommended water-heating solution. They are fairly simple to install, rely on air (you do not get a more abundant natural resource than that!) and above all, can significantly cut the cost of water heating. We do, however, believe solar water heaters can be equally efficient, depending on where you live and your unique energy requirements.”


Read about it in the press:

Business Tech – Heat pump vs solar energy – here’s what saves you the most money

SA Property News – What to consider when choosing an alternative water heating system