Two technologies for different purposes, both of which will replace electricity supplied from the grid.

A. Solar electric or solar photovoltaic generates electricity from solar photo voltaic panels.

B. Solar thermal, or solar water heaters replace the electricity used in heating water by an electrical resistance element.

Frequently the two types are considered by the layperson to be the same.

They are not, and only really share one common symptom, in that they both use solar radiation, or put another way, the sun to either generate of electricity, or to heat water.


At 2017 solar electric (PV) is considerably more expensive to purchase than solar water heaters when electricity savings in kWh are the goal.

For example, a solar PV system will cost almost double the cost of a solar water heater if it is going to be used for heating water.

But while a solar water heater is cheaper, it cannot produce electricity, so cannot be used for lights or other electrical appliances.


Electricity consumption in the home is spread across all the electrical appliances and lighting.

The really heavy users of electricity are the electric geyser, kettles, hot plates, hair dryers, tumble dryers, electric radiators, toasters or put another way anything that produces heat.

The low consumption items are TV’s, computers, decoders, hi fi, clocks and lights.

Water heating with an electric geyser in South Africa will typically be 35%-60% of the homes monthly bill.


As water heating uses so much electricity it is the place to start.

As the price of electricity has increased year on year, solar water heaters have become increasing attractive from a cost to reward perspective. Back in 2008 Eskom the power company introduced incentives or rebates to go solar. They finished in 2015.

There are no incentives to switch to solar today.

However because the price of electricity has gone up so much, the cost to reward ratio in 2017 is now better than it was at any time during the rebate program.

In the case of Ubersolar, the payback on a solar system can be as little as 18 months. Taking into account projected electricity price increases, on a very conservative basis, the investment returns can be over 800% over 10 years after the cost of the investment.

No other investment is likely to achieve any thing like these sorts of returns.


In the home if you have mains power it probably does not make economic sense to go for solar electric (PV) for another for 5 -7 years (post 2022).

The reason is simply down to cost. Unlike solar water heaters where the hot water is stored in the geyser or tank, with solar electric batteries are required to store the electricity for use at night.

Batteries are still expensive and depending on the type, have a limited life as to the number of cycles that can be discharged. Taking into account that the batteries will have to be replaced at some time in the future, 5 to 15 years, when the cost per kWh is calculated the price of using solar power at night is close to double using power supplied by Eskom or the local municipality.

In 5 to 7 years time when almost certainly battery technology will have fallen even more in price, and the price of electricity has risen, the financial equation will change in favour of producing your own electricity and storing it, and using it rather than buying mains power.

The financial equation is different in businesses that use electricity in the daytime. For example a shopping mall uses electric light during the day and at night uses far less. So in these cases limited battery storage is required, and the cost reward ratio can make sense to go with solar PV today.


Although the financial equation is self evident, other factors do also come into play. Solar PV panels have increased in efficiency, typically about 15%-20% but solar water heater collectors are typically double that and more.

Further the cost of the solar PV collectors is double the cost of solar water heater collectors.

Overtime this gap is likely to narrow, but in 2017 heating water with solar PV panels is approximately double the cost of the solar water heating technologies.


The time for consumer to save money with solar water heaters has already arrived. The time to save electricity for areas such as lighting is still a few years away.

The issue that faces all renewable energy is one of cost. Until renewables are cheaper than carbon based electricity, they face an uphill battle.

In South Africa as solar radiation is approx. double most of Europe, and the price of electricity is rising, all electricity saving makes sense, it is just a question of when you should do it.

For solar water heaters the time is now, for solar electric in a few years time.