How much electricity do solar panels produce?

If you’re thinking about installing solar panels on your property, finding out how much electricity they supply is a great starting point before investing. With this knowledge, you’ll be able to calculate if they’re a worthwhile renewable energy source for your home and lifestyle. If you live in South East England, for example, you could lower your bill by as much as £610 per year, meaning the cost of solar panels could be paid off in a decade, while reducing your carbon footprint by 0.78 tonnes of carbon dioxide per year, too. 

How much electricity your panels will produce depends on a number of factors, including the type of photovoltaic (PV) panels you have, your location, and the orientation and angle at which the panels are installed. How much energy produced overall will naturally also be related to the size of your solar array and the individual efficiency ratings of your panels.

Solar panel production is measured on how many kilowatts (kW) of electricity are used per hour (kWh). For example, a typical 4kW system will typically generate 3,400kWh of electricity each year.

“The general estimate is that the average three-bedroom home in the UK will use just over 3,000kW annually,” says Martin Desmond, Managing Director of Wizer Energy. “Therefore, the typical solar panel array in the UK is 3kW or 4kW.”

A typical 300 watt (W) solar panel can produce ​​around 922.5 watts per hour (Wh) per day and, for higher efficiency solar panels, this can increase up to 1.3228kWh. 

Sunshine duration has been gradually increasing over the years and the annual sunshine duration recording sits between 1,500 and 1,600 hours for 2022-23. This has increased the amount of energy solar panels produce in a day and will affect calculations if you would like to manually work this out. 

The typical solar panel delivers between 200-450W in the UK, so, we will use the SunPower Maxeon 5 AC solar panel, as an example. It has an efficiency of 22.60 per cent and a power output of 415W. The average duration of sunshine for the UK is 4.25 hours per day, therefore a calculation of the panel’s energy output is: 

415W x 4.25h = 1,763Wh (1.76kWh) per day

To calculate how many solar panels you require, you’ll need to understand how much electricity your household uses. According to Ofgem, the average UK household of two to three people uses 2,900kWh of electricity per year, working out at 242kWh per month and 7.2kWh per day. 

For the average home to use the SunPower Maxeon 5 AC panel, they would need to divide the desired  electricity usage per day by the the panel’s wattage, to work out the number of panels required:

7,200Wh ÷ 415W = 17 panels

A 3.5kW solar PV system is most typical for the UK and will have around 12 panels in total, but this will be affected by location, number of people inhabiting the house and weather conditions. The size of your roof will also be a limiting factor for many homeowners. 

As it is rare for even the best solar panels to completely compensate for a household’s entire energy usage (thanks to reduced production in the winter months), most homes with solar are still connected to the national grid and will utilise it at some point in the year. If you do want to rely mostly on solar, you should invest in a solar battery to store excess energy generated.

When installing, make sure your solar PV system is well designed for your home’s orientation and location. Solar panels run on light to produce energy and, while they can still produce energy when it’s cloudy, if it is very overcast they will typically deliver only 10-25 per cent of their normal power output. Quality solar panels are better designed to cope with shade and other environmental factors that may impact their output rates.

To make sure yours can reach their maximum energy production every day, you should keep solar panels clean. To properly maintain solar panels, keep them free from leaves, branches and debris that could block sunlight, and remove aerials where birds may perch, so their droppings are less likely to fall on the solar panels, reducing efficiency.

A great way to measure the electricity that your solar panels are producing is by connecting them to a smart meter. If you haven’t already got one installed, doing so (whether or not you have solar panels) could help reduce your carbon footprint at home and lower household bills, as you’ll have accurate, real-time readings of your overall energy usage.

Plus, if you qualify for the Smart Export Guarantee (SEG) scheme, it’s a simple way to see how much excess energy you can put back into the grid.