Solar Power: FAQs

Is my house suitable for Solar Photovoltaic panels (Solar PV)?

The main considerations for Solar PV are:

• Roof orientation – south facing roofs generate most electricity, but east and west facing roofs might generate 10% less than a roof facing due south.
• Roof slope – solar panels work best on sloped roofs. They can be installed on flat roofs, but may cost more to install and generate less electricity.
• Shading – if your roof is shaded (e.g. from nearby buildings, trees, chimneys, etc.) for significant parts of the day, especially between 10am and 4pm, then the amount of generation can be significantly reduced.
• Roof condition – the structure of your roof must be able to support solar panels.

How much solar can I install?

You can export up to 3.68kW per phase (11.04kW for a three-phase connection) to the grid without needing permission to connect to the electricity grid. This limit is based on the inverter output, so typically up to 4kWp of solar panels can be installed per phase.

You can apply for a larger export capacity, but this might incur additional costs to upgrade the electricity network in your area. In most cases, the size of an installation is limited by the number of panels that can fit on a roof which, for many houses, is less than 4kWp.

It is also worth considering how much electricity you use to make best use of your own generation, rather than exporting lots of electricity to the grid.

Do I need planning permission?

For most houses, domestic solar panels can be installed under permitted development rights, so no planning permission is necessary. However, in some cases, planning permission is required:

• If your house is listed then you need listed building consent, even if the panels are mounted on the ground within the property’s curtilage.
• Designations such as conservation areas, Areas of Outstanding Natural Beauty and World Heritage Sites have constraints on where panels can be installed on your house and land under permitted development rights, especially where the panels would face a public highway.

For more guidance, you can check the online Planning Portal.

If you’re not sure if you need planning permission, then you can contact Cornwall Council for guidance.

How much does it cost to install?

Solar installation prices plummeted during the 2010s, but there has been some volatility in prices since the COVID pandemic, and further price reductions are expected going forward. The costs below are based on government average figures for the UK in the 2022/23 tax year, but please note that prices can vary depending on several factors, such as complexity of the install or the quality of the panels installed. You might find local installers that can install a system for lower prices, and so getting several quotations will help you compare which supplier and system is best for your situation.

How do I get my money back?

You will save money by using the electricity you generate, which reduces the amount of electricity you need to buy from the grid, and you can also sell electricity back to the grid. On-site consumption of electricity offers the biggest financial benefit, because the amount you save for every unit of electricity you don’t buy, is greater than the amount you can be paid for each unit you export to the grid. So, houses that use more electricity in the daytime, typically have bigger savings than those that use more in the mornings and evenings.

Table assumes import rate of 30p/kWh, export rate of 4.1p/kWh and 1/3 of generation is used on-site.

How much might I save?

Savings are based on how much electricity you use on-site and the price of your import tariff. The higher your tariff and the more electricity that you use in the daytime, then the higher your savings.

How can I increase my use of electricity generated?

Plan to use appliances, such as washing machines, in the middle of the day when your solar panels are generating the most electricity, especially when it is sunny.

If you have a hot water cylinder with an immersion heater, consider fitting a power diverter to divert excess generation to a hot water cylinder. Potentially, this can provide up to 50% of your hot water over a year. Savings would depend on how much you pay to heat your hot water, compared to how much you get paid to export your excess generation.

If you have an electric car, then you can charge it in the daytime. Some electric car chargers can be programmed to only use any excess generation that would otherwise be exported to the grid and charge your car instead.

Domestic batteries can store excess electricity, although currently the costs of installing a battery, in most cases, will outweigh the savings.

Can I sell electricity to the grid?

Installations installed after 2019 can still sell electricity to the grid under the Smart Export Guarantee (SEG) scheme. To receive the SEG, you must have a Microgeneration Certification Scheme (MCS) registered installation and a smart meter. The SEG is paid by energy suppliers and the rate they offer is different per company. It currently ranges from as low as 1p/kWh to 15p/kWh. Your SEG supplier doesn’t have to be your energy supplier, so you can shop around. Some SEG suppliers offer much better rates for existing customers who buy electricity from them.

Can I switch energy supplier with solar panels?

Yes, you can.

My panels were installed before 2019, what should I be receiving?

If your panels were installed before April 2019 by an MCS registered installer, then you should be receiving the generation Feed-in Tariff (FiT) and the export tariff. New applications for FiT have now closed.

The generation tariff pays a set amount for each kWh the panels generate, and the export rate pays a deemed rate, which assumes 50% of your generation is exported and 50% is consumed on-site.

If the energy supplier paying your FiT payments was one of those that have ceased trading, then your right to receive Feed-in Tariffs will not be automatically transferred to your new electricity supplier. You will have to find a new supplier to make these payments.

How much does maintenance cost?

Solar installations don’t typically require any maintenance and the panels are designed to be self-cleaning when it rains. Some installers offer an annual maintenance check for peace of mind, but this isn’t normally required.

The inverter, which converts the direct current that the panels generate into alternating current, which is used in your house, will usually need replacing, typically between 10 and 15 years after the original installation. A new inverter will typically cost between £500 and £1,000 to install.

The rest of the system should last at least 25 years and while there will be a small degradation of the output of the panels, overall, the long-term performance of your system should still be providing good levels of generation.

I’ve been offered free solar panels, is this a scam and will I have problems if I try and sell my house?

Free solar installations installed before 2019 were often owned by a third party, using an arrangement known as a ‘rent-a-roof’ scheme. At the time, it was financially attractive for companies to install panels and claim the generation Feed-in Tariff (FiT) and the export tariff. Households benefitted from reduced electricity bills by consuming on-site the electricity the panels generated.

Occasionally rent-a-roof schemes have raised concerns from conveyancers dealing with house sales, but usually provision of the relevant leases and paperwork will resolve this; sometimes a change of ownership may mean that the homeowner needs to buy the installation or carry out remedial work if the panels weren’t installed properly in order to sell the house, but this is rare. New owners may have to pay maintenance costs for a rent-a-roof solar installation.

Currently, rent-a-roof schemes are unusual and new, funded installations typically become the property of the homeowner, rather than a third party. This is because there is no longer a financial incentive for a third party to own them.

Companies that install measures using the government’s ECO4 grant regularly offer free solar installations. However, these are largely speculative offers and due to the highly restrictive eligibility requirements for the grant, most offers don’t lead to any actual installs; alternatively, insulation and a heat pump must also be installed alongside or instead of a solar installation.

If you have been offered free solar PV and don’t know if it’s a scam or not, then you can contact us for our advice. Just contact our Cornwall Low Carbon Energy Advice Network team at email: lowcarbon@cep.org.uk to request a call back.

How much funding is there for solar PV?

Currently, there is no funding specifically for solar PV, but there are schemes that can consider solar as part of a larger whole house retrofit approach.

Is it worth having a battery as well?

At the moment, batteries are generally not a good financial investment. They will help to keep your bills lower, but they are expensive to install and so will increase the payback period of the overall solar PV system.

If I switch to electric heating, will solar panels and a battery provide all my heating?

No! Solar panels, even with a battery, would make a negligible difference to your heating your house with electricity. This is because a typical solar installation generates less energy than most houses need to heat over a year. Most of this electricity is generated in the warmer months of the year, in the middle of the day, when little heat is required.

How do I know if my panels are working properly?

Your installation will have a generation meter that shows how much electricity your solar panels have generated since they were installed. If you check this meter regularly and notice that the generation is less than expected for the time of year and recent weather conditions, it might indicate a fault.