by Joanna O’Loan
If you want to reduce your energy bills and carbon footprint, then installing solar PV can be a good choice. There are cost, technical and lifestyle questions you will need to consider. Can you afford the cost of the panels? Do you have an appropriate site for the panels? When do you use electricity and how much of that can you use while the panels are generating?
What is solar PV?
Solar panel electricity systems, also known as photovoltaics (PV), capture the sun’s energy using photovoltaic cells. One of the most familiar forms of renewable technology, we’re all used to seeing solar panels on the roofs of homes and public buildings across the UK.
It works by converting sunlight into electricity via the PV cells, which can power household appliances and lighting.
How much will the system cost?
The cost varies depending on your local area, your installer and the type of panels you want – but as a guide, you can expect to pay around £4,000 – £5,000 for a typical, 3.5kWp system.
This system would require around 20m2 roof space for the panels. This cost includes the other hardware of the system – the inverter, generation meter, panel-mounting system and the wiring, as well as the cost of labour for supplying, installing, connecting and registering the system, and scaffolding for most roof-mounted systems.
Once installed, you can expect the system to last for 25 years. It’s unlikely to need much maintenance in that time. Rainwater should wash your panels, but some areas will notice more dust settling on their panels that might need cleaning. Typically, the manufacturer’s warranty will cover any faults in the PV panels – but make sure this is in place before agreeing to an installation.
One piece of equipment that probably will need replacing is the inverter. The inverter’s job is to change the type of electricity generated by your panels (DC) into the type of electricity that powers your household and export to the National Grid – (mains voltage AC). Usually an inverter lasts around 10-12 years, so likely to need replacing at least once during the system’s lifetime. You can expect to pay around £600 to £800 for a replacement.
You should also keep an eye on any nearby trees – and cut them back if their branches begin shading the panels. Any shading will reduce the performance of your system.
Check our Solar Energy Calculator to find out how much energy you could generate from a solar installation at your home. Read on for more tips on areas to consider.
Soup up your solar
There are several things to do to make sure you’re maximising the performance of your solar PV system.
You will need to site the system in the best place, and your installer will help with that. The best sites avoid shading and face somewhere between southeast and southwest, angled between 30 and 50 degrees from horizontal.
A well-sited 3.5kWp system could generate over 3,000 kWh per year – or almost as much electricity as the typical household would use. However, most households will export a lot of this electricity, as you won’t necessarily use enough electricity at the time it’s being generated.
Energy Saving Trust’s solar PV page has estimates of how much power you can generate in different areas of the UK, and how much of that electricity you’re likely to use (self-consume) based on how often you’re usually at home. These numbers can give you a rough estimate of your likely annual generation, matching your most common occupancy pattern.
Solar PV panels pay for themselves more quickly when you use more of the electricity yourself. Try to use your appliances during the day, although not all at once to avoid needing more electricity than your system is generating. You could consider using appliance timers to help you do this if there is no one home during the day.
You could also consider investing in a solar diverter (to heat up your hot water cylinder when the sun shines).
What about batteries?
A battery can store the surplus electricity you’re not using, for use at night when your solar PV system isn’t generating. Using the stored electricity from your battery is free, rather than importing electricity from the grid, charged at your tariff rate – but the question is, whether the initial cost of the battery is worth the bill saving you make?
Costs depend on the type and size of battery you opt for, but you could expect to pay around £5,000 to £8,000 for most domestic size installs. In many cases this wouldn’t lead to a return on investment for the battery. However, prices are continuing to fall and technology is improving, so battery storage is likely to become a viable economic option for more households.
For the time being, it seems for most households, the best option is to try and use as much of your electricity while your PV system is generating it.
People choosing to install a domestic battery may base that decision on their wish to be more independent of energy companies, rather than saving money for now.
But, installing a battery does allow you to make the most of the energy you generate, and there are new opportunities emerging for using batteries in other ways, such as smart time-of-use tariffs that mean you can charge and discharge the battery to make the most of the cheapest rates.
Find out more in our blog on whether home energy storage is right for you.
What about electric vehicles?
Electric vehicles, or EVs, are another way to store and use electricity from your solar PV installation. An electric vehicle is effectively an electric battery on wheels. Your solar PV system could charge your car or van, saving money petrol or diesel or from charging elsewhere, as well as potentially reductions in road tax. You would need to have your EV plugged in during the day in order to maximise electricity generated via your solar system.
What happens if I don’t use or store the electricity?
Any surplus energy is exported to the grid for other people to use and signing up for a Smart Export Guarantee can make sure you are paid for supplying that electricity.
The Smart Export Guarantee (SEG) is the support mechanism designed to replace the Feed-in Tariff scheme. It doesn’t work in the same way, but it’s an option for small-scale generators to be paid for their export.
It’s been in effect since 1 January 2020.
There are two main types of tariffs – flat rate and variable.
Electricity demand fluctuates across the day and the wholesale price changes with it. A flat rate tariff pays you the agreed rate no matter when you export. A variable rate tariff will change the price paid depending on when you export. The energy supplier will track wholesale prices – so the rate will increase with demand.
The company that provides your SEG doesn’t need to be the same company that supplies you with electricity, although some companies will offer you an export tariff for signing up to their supply, too. Be sure to check through their terms and conditions.
You should shop around for the best SEG tariff, much like you might for your gas or electricity supplied now, and continue the review SEG tariff options regularly.
Find out more in our guide to the Smart Export Guarantee.
There are advantages to installing solar PV, and if you want to go ahead – the next step is to speak to some Microgeneration Certification Scheme (MCS) certified installers and get some system designs and quotes tailored for your home.