The average household in the UK uses 3300 units of electricity (kWh, or kilowatt-hours) of electricity each year. Based on an electricity price of 12.5p per kWh this costs over £400. An average domestic solar PV installation in the south of the UK can cut your electricity bill by up to 50% depending on your circumstances.
Solar PV systems are measured in terms of kilowatt-peak (kWp) – this is the amount of power a system can generate under standard test conditions. A 3kWp system in the south of England can produce approximately 2850kWh per year – over 80% of the average consumption. However, most electricity is generated during the summer and none is produced at night at any time of the year, so you will have to keep on buying electricity from the grid during the winter and in the evenings.
To maximise your savings, you should try and use most of your electricity during the day when the solar panels are producing free electricity rather than at night when you will have to pay for it. For instance, your washing machine uses a lot of electricity so you should try and use it when you are producing a lot. If you work from home or are retired you can put it on during the day, or else some machines let you use a timer to automatically switch it on. Buying energy efficient appliances such as those recommended by the Energy Saving Trust can save you even more money.
The south of the UK receives approximately 20% more sunlight than the north, so you will be able to generate 20% more electricity here. Orientation is also important – a south-facing roof will generate more than an east- or west-facing roof, and the slope of your roof can also make a difference. Finally, the size of your roof will determine the maximum number of solar panels you can install. A solar installer will be able to asses your property and give you an estimation of the power output.