Should I Install Photovoltaic Solar Panels?
Solar panels can help to bring down energy bills and reduce our carbon output. Here’s what to know about installing them
Professional advice from: Kit Knowles of Ecospheric; Rich Tyers of Rich Tyers Studios; Alan Budden of Eco Design Consultants
The answer is simple: “To reduce your carbon footprint and energy bills,” Alan Budden says.
If you’re patient, over time the panels should save you money, as you’ll generate a significant chunk of your own electric power, rather than paying an external domestic supplier. “There’s a well-established track record of value for money,” Rich Tyers says. “In general, the payback period is 10 to 20 years.”
If you generate more electricity than you consume, you can also sell this back to the National Grid, Kit Knowles points out. “There can be real value in this. Previously, it was only worth a couple of pence per kilowatt-hour (kWh). Now, there are symmetrical tariffs where you can get paid the same amount you pay for your energy,” he says.
According to the Federation of Master Builders, if you install an export meter and feed excess power back to your supplier, you could earn 6p to 9p per kWh.
No wonder more of us are taking the plunge. Trade association Solar Energy UK anticipates 200,000 installations by the end of 2023, up from roughly 139,000 in 2022, and around 46,000 in 2021.
As well as being more efficient, affordable and lower-maintenance than they used to be, PV panels are also relatively simple to install.
“Unlike a lot of energy upgrades, solar panels can be installed with minimal intrusion, assuming there aren’t significant technical barriers to installation, such as needing structural upgrades to a roof,” Rich says. “Where PVs make so much sense is on buildings that need a new roof anyway,” Kit adds.
Another potential bonus is that a new generation of PV panels are designed to physically make up your roof, rather than sit on top of it (the solar panel ‘look’ we’re all familiar with).
Before you even contemplate installing PVs, always tick off other factors first, Kit stresses. There’s no point fitting PVs to a home that’s not fit for purpose.
“The first thing you should do is make sure your buildings are functionally sound and weathertight,” he says. By this, he means fixing leaks, mould, subsidence, ventilation, insulation and airtightness.
Ventilation should be top of the list. “You don’t insulate – that is, treat your ‘thermal envelope’ – unless you ventilate at the same time with a system that uses heat recovery, such as a mechanical ventilation and heat recovery unit (MVHR). To treat your thermal envelope, you look at air tightness, moisture flow and insulation,” Kit says. Next, he suggests, homeowners should “focus on conservation of energy principles”.
“The most efficient and cost-effective kilo of carbon saved is that which was never consumed in the first place,” he says. “The sweet spot is to conserve energy while also generating it.”
Once your home is sound, he says, then you can look at active technologies such as PVs, but it shouldn’t be the first pound spent.
Solar panels harness the energy of the sun, converting it into electricity. Albert Einstein first described this “photoelectric” effect in the early 19th century.
“Solar panels are filled with a semi-conductor material (for example, silicon) that is [typically] housed in a glass casing on a metal frame,” Rich explains. “When the semi-conductor material is exposed to photons (for example, particles in sunlight), this releases electrons that produce an electrical charge.
“This charge creates an electrical direct current (DC) that’s captured by wiring within the panel,” he continues. “This is then run through an inverter to convert the direct current to an alternating current (AC) that’s suitable for appliances within the home.” Wiring can also then connect to the National Grid.
Today’s PV systems also commonly contain batteries, which hold electricity to be used by a homeowner or sold back to the Grid. “This allows homeowners to use their generated electricity throughout the year, including at night,” Rich says.
“One caveat is battery capacities are usually quite small, so you could run a whole house for, perhaps, 12 to 24 hours before it runs out,” he says. “Of course, the time this takes would vary greatly, depending on your use of energy and how big your home is.”
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According to data from the Energy Saving Trust, a 3.5kW solar panel system costs roughly £5,500 to install. (For a larger, five-bedroom house, you may be looking at around £11,000, according to estimates at The Eco Experts.) This would generate approximately 2,645kWh of energy annually.
Ofgem estimates the typical household in Britain uses 2,900 kWh of electricity and 12,000 kWh of gas in a year.
“Prices vary dramatically, depending on the size of the array and what’s specified,” Rich says. “The cost of materials and labour is quite volatile at present. Homeowners also need to take into account access arrangements, such as scaffolding, which can add a material amount to the total cost.
“For precise cost advice,” he says, “I would recommend homeowners speak to a local installer, who could quote accurately. All that caveated, I would budget £15,000 to £25,000 for a good-sized array.”
This might sound a lot, but the average UK household energy bill is now more than £2,000 a year, according to Ofgem. The Energy Saving Trust suggests solar panels typically cut your electricity bill by 15% to 25%, but this may be more. Any initial outlay (if you can afford it), can be measured against future savings over the lifetime of your panels.
Kit says one reason PVs are shifting up the priority list is, as mentioned earlier, because homeowners can sell back excess electricity, offsetting their bills. “There’s growing economic value in exporting energy and you can generate energy even when you’re not using it,” he says.
Solar panels are also exempt from VAT, as are batteries (though only if they are installed at the same time).
Kit says the configuration of your home and its occupants’ lifestyle will impact how efficient panels are. “While we generate our energy in the middle of the day, we tend to consume in the mornings and evenings,” he says.
He suggests an east-west configuration is most efficient. “It means you’re generating energy when the sun rises and sets – times when we tend to consume most energy. Even north-facing pitches can be utilised as long as the pitch is shallow (less than 20°).
“If dealing with flat roof or ground-mount arrays,” Kit continues, “east-west can result in much larger peak generation potential, as south-facing needs gaps between banks to prevent self-shading, so you won’t fit as many on.”
“Panels need to be sited in an area that will receive plenty of sunshine and will not be overshadowed by trees or buildings throughout the year,” Rich adds. “Overshadowing greatly reduces the efficiency of solar panels (and, therefore, reduces or invalidates the payback period), so this is an important point.”
Rich advises that panels should be kept clean and well-maintained to be efficient. “Ensure the panels can be relatively easily accessed for cleaning, maintenance, repair and replacement,” he says.
“If the panels need scaffolding to access, this means a significant cost every time they need maintenance,” he says. “Again, ask your installer, and develop a clear strategy for safely accessing the panels throughout their lifetime.”
Another consideration that’s often overlooked is wildlife. “Solar panels need to have an air gap between the underside of the panel and the roofline in order to stay well-ventilated and cool,” Rich explains. “Panels get quite warm throughout the year, so can be ideal spots for birds to nest.
“I suggest installing guards that prevent birds and animals from accessing the underside of the panels, but that still maintain ventilation,” he says. “Proprietary bird mesh products are available that installers should be able to advise on.”
Your pro should be happy to talk you through any previous installations and answer any questions about the process. If you’re working with an architect, they may be able to recommend an installer directly.
You can also check if your installer is registered with any regulatory boards. “I suggest looking at the MCS (Microgeneration Certification Scheme), which provides certified products and installers,” Rich says. “MCS also publishes design and installation standards that MCS Certified Installers must follow.
“Homeowners should check with the installer that appropriate structural surveys and checks have been carried out,” he adds.
Read more stories looking at sustainability in home design.
Generally, you won’t need Planning Permission. “Solar panels are [usually] considered Permitted Development,” Alan says, “unless they protrude more than 150mm from the roof plane, or when you don’t have Permitted Development because it’s removed – for instance, if you’re in a conservation area or the building is listed.”
If you’re unsure, seek advice. “It will depend on where the customer wants to place the panels and any planning constraints on the property,” Rich says. “Installers will often leave the responsibility of Planning Permission to the homeowners, so it’s important to seek clear advice on this. Local council planning departments can offer advice, usually for a fee.”
Even if you do live in a listed building, don’t assume you can’t have solar panels. You can apply for Listed Building Consent from your local council and then apply for Planning Permission.
“Historic England is now part of the Climate Heritage Network and has started to accept PV installations, even on Grade I listed buildings,” Kit says. “The Historic Environment Forum works on the issue of energy conservation in old listed buildings that typically consume disproportionately huge amounts of power for heating.”
Panels could also be installed discreetly in gardens and on outbuildings in listed properties.
You should ask your installer about this. “Solar panels need to achieve a certain fire rating if they’re within a certain distance of the property boundary,” Rich says. “This is described within the MCS standards and Building Regulations. It’s something the installer should be aware of; they should specify panels that meet the fire requirements of the Building Regulations.
“As homeowners, it’s worth sending a note to your installer checking that the panels are specified to the correct fire performance,” he adds.
Have you installed solar panels on your home? Share your tips and photos in the Comments.