Now more than ever, people are concerned about the health and longevity of our planet. Plastic bag usage is down in the UK since charging for use came in and many Brits are trying harder to make their homes as eco friendly as possible. Some of the ways you can do this include increasing your insulation to minimise heat loss, recycling plastic, cardboard and glass, and using a food caddy to throw out compostable food waste.

In addition, the number of solar panels installed in the UK doubled between 2018 and 2019 and there are now over one million homes utilising this technology to create renewable energy. While some people may be put off solar due to the cost of installation, when combined with a heat pump, you could heat your home using mostly solar energy. 

Can you run a heat pump on solar?

You can combine a heat pump heating system with solar panels to ensure that your heating and hot water needs are met while also being environmentally friendly. It’s entirely possible that solar panels would be able to produce all the electricity you need to run your heat pump depending on the size of the solar array. That is, on balance you would generate more electricity than you would use over the course of a year, although this would not be applicable to night time usage.

There are two different types of solar energy - solar thermal and photovoltaic.

As solar thermal uses heat from the sun to warm your hot water, this can help reduce the electrical energy required by the heat pump to meet your needs.

In contrast, solar photovoltaic (PV) systems convert energy from the sun into electricity. This electricity can be used to help power your heat pump, reducing your need for electricity from the grid that is mostly created by burning fossil fuels.

Generally, solar panel systems are sized in kilowatts (kW). This measurement refers to the amount of power that is produced by the panels per hour when the sun is at its strongest. The average system is around three to four kW and this reflects the maximum output that can be produced on a very clear sunny day. This figure could be less if it’s cloudy or during early mornings and evenings when the sun is at its weakest. A four kW system will generate around 3,400 kWh of electricity per year and will take up around 26 m2 of roof space.

But is this enough?

The average UK home uses around 3,700 kWh of electricity per year, meaning that a four kW solar panel system should almost provide all the electricity you need. A small percentage would need to be used from the grid.

However, it’s worth noting that the average property uses a boiler, and not a heat pump, to provide heating and hot water. In these homes, gas consumption will be higher and electricity usage lower. But heat pumps use more electricity - even one that is very efficient with a CoP of four uses around 3,000 kWh per year. This means that while solar panels should be able to produce most, if not all, of the electricity that you need to heat your home and water, they are unlikely to be able to power both your heat pump and other appliances without assistance from the grid. Based on the figures above, the solar panels should be able to provide around 50 per cent of the electricity the household would need in total, with the remaining 50 per cent coming from the grid (or from other renewable methods, such as a small wind turbine if you have one installed). 

How many solar panels do I need for a heat pump?

When it comes to solar panels, the more you can fit on the roof the better. Too few panels and they could barely power even the smallest of electrical devices.

As discussed above, if you want solar energy to power your heat pump, the solar panel system would probably need to be at least 26 m2, though you may benefit from having more than this.

Solar panels can vary in size depending on the manufacturer, but they’re bigger than you might think. On a house, they look relatively small, but each panel is around 1.6 metres tall by one metre wide. They have a thickness of about 40mm. The panels need to have a large surface area so that they can take in as much sunlight as possible.

The number of panels you will need depends on the size of the system you want. Typically, four solar panels are needed per one kW system. Therefore, a one kW system will need four solar panels, a two kW system eight panels, a three kW system 12 panels and a four kW system 16 panels. The latter creates an estimated surface area of around 26 m2. Bear in mind that a four kW system is ideal for a household of three to four people. For more residents than this, you may need a five or six kW system that could require up to 24 panels and take up to 39 m2.

These figures will be dependent on your roof size and your location, meaning you may need more or less.

If you’re considering having a heat pump installed, and using solar panels to power it, you should ensure that you get a suitably qualified engineer to look at your home. They will be able to advise you on how to make your home more efficient (for example, by installing double glazing, additional insulation, etc.) so that less electricity is needed to power the pump to replace the heat that is lost. They should also be able to tell you where the heat pump can go and how many solar panels you will need.

It’s absolutely worth getting professional advice so that the installation goes smoothly.

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