Why a Heat Pump Makes More Sense with Solar PV

Solar PV has become a popular choice for South African homeowners looking to reduce their electricity costs. One of the biggest energy users in a home is the geyser, which naturally raises the question: should you use your solar panels to heat the geyser directly?

It sounds like a good idea. However, there is another option worth considering.

Combining a solar PV system with an efficient heat pump can make better use of your available roof space while still providing plenty of hot water for your home.

The problem with using PV to power a geyser element

A conventional geyser uses an electrical element to heat the water. If the element is rated at 3 kW, it uses electricity to produce heat at roughly a 1:1 ratio. In simple terms, one unit of electricity gives you approximately one unit of heat.

There is nothing wrong with this technology. It has been used successfully for many years.

The issue is what happens when the geyser reaches its required temperature.

The element switches off.

Your solar panels may still be producing electricity, particularly during the middle of the day when solar generation is at its highest. That electricity then needs to be used somewhere else in the house, stored in a battery, exported to the grid where possible, or potentially curtailed.

There is also the question of roof space. If a large portion of your solar PV system is being sized around the electricity needed to heat water, you may need more panels than you otherwise would.

A heat pump changes the equation

A heat pump works differently from a traditional geyser element.

A heat pump works a little differently from the element in a normal geyser. A heat pump doesn’t heat water in quite the same way as the element in a normal geyser. It takes heat from the air around the unit and moves that heat into the water. Electricity is still needed, but far less of it is required to produce the same amount of hot water.

For example, a heat pump with a COP of around 3.5 to 4 can deliver roughly 3.5 to 4 units of heat for every unit of electricity it uses. That’s a big difference when you compare it with a standard geyser element, where one unit of electricity gives you about one unit of heat.


Of course, the exact performance won’t always be the same. Things like the outside temperature, the temperature of the water and how the system has been installed all make a difference. Even so, the saving compared with a traditional geyser element can be significant.

Your solar power can be used throughout the home

This is where the combination of solar PV and a heat pump becomes particularly useful.

During the day, your solar panels produce electricity. If the water temperature has dropped, the heat pump can use some of that available electricity to heat the water.

Once the water reaches the required temperature, the heat pump stops.

The solar panels can then continue supplying electricity to the rest of the house.

Your refrigerator, washing machine, computers, lights and other appliances can all make use of the available solar energy. If you have batteries, they can also be charged.

Instead of dedicating a large amount of solar generation to a conventional heating element, the energy can be shared across the household.

Making better use of your roof

For many homeowners, roof space is limited. You want every solar panel to contribute as much as possible to reducing your reliance on grid electricity.

Using an efficient heat pump means you don’t necessarily need to generate as much electrical energy specifically for water heating.

This can be particularly helpful in designing a new solar installation. Instead of just adding more panels to a high demand geyser element, you can think about the total energy needs of the house and use a heat pump to reduce the amount of electricity needed to produce hot water.

A practical combination for South African homes

Solar PV and heat pumps work well together because they perform different jobs.

The solar panels generate electricity. The heat pump uses that electricity efficiently to produce hot water. When the hot water is ready, the heat pump switches off and the solar power becomes available for other household requirements.

It is a simple concept, but it can make a meaningful difference to how efficiently your solar system operates.

At SunScan, the focus is on helping homeowners find practical and energy-efficient solutions for hot water.  A heat pump, combined with correctly sized solar PV, can help you make better use of your available roof space while reducing the electricity required to heat your water.

The goal isn’t simply to install more panels.

It is to get more useful energy from the panels you already have