Living with Solar Panels – A Self Build Expert on the Benefits of Installing his Solar PV System

Are PV Panels Suitable for My New Build or Home Renovation?

Solar panels are most productive facing south at an angle between 30° and 40°, which happily matches the standard roof pitches of UK homes. Ideally, your plot or existing property should have a southerly aspect, although roofs that face south-easterly or south-westerly can also work. Even flat roofs can be fitted with solar panels on specially angled brackets.

For an average PV system that produces around 3.5kW at peak efficiency, you will need between 10m² and 20m² of suitable roof space, which equates to between six and 12 panels (depending on the individual panels’ output). The stronger the sunlight, the more power is generated, however, even when the sky is very cloudy, daylight will still be effective.

Though PV arrays are typically placed on rear aspects to avoid disrupting facades, where this is not possible they can installed to the front elevation. Photo: Treadlighter

To maximise production, no panel should be overshadowed by trees, chimneys or neighbouring properties between the hours of 10am and 4pm throughout the year. If this isn’t possible, they can be fitted on garages, garden offices or anywhere on your plot that receives sufficient daylight – though you may need to extend the electricity supply.

PV installations count as permitted development, so no planning permission is needed unless you live in a conservation area, a listed building or your panels protrude more than 200mm above the roof height. If you’re dealing with a protected property, one option for gaining approval is to opt for specialised solar roof tiles, available from companies like Solex and GB-Sol. These can mimic clay tiles, slate and even textured glass, though they are more expensive than standard units.

Can I Access Any Funding for Solar Panels?

A major benefit of PV is the ability to sell electricity you don’t use to the grid. Under the Smart Export Guarantee (SEG) scheme, major energy suppliers are required to pay a set rate for each kilowatt hour (kWh). Rates vary dramatically, so you may want to consider moving suppliers to take full advantage of the payments.

SEG replaces the old 25-year (later 20-year) Feed-In Tariff, which ran from 2011 to 2019 and offered payments originally for 25 years (later 20 years). Renovators may buy a property where the tariff is still in operation. Originally generous, the Feed-In Tariff is much less so today, but the payments are based on total power produced, not just the amount exported.

Can Solar Panels Help Me Save Money?

The success of a solar PV installation depends on matching your panels’ production with your household needs. If, for example, your home is unoccupied during the day, most of the electricity created will go to the grid. The payments you receive for this are substantially less than the grid charges you for electricity. If you work from home, have a young family or are retired, however, bright sunshine is the signal to turn on your most energy intensive items, from washing machines to immersion heaters, which will effectively be free.

Flat roofs can also accommodate PV panels using specially angled brackets. Photo: Treadlighter

Smart home systems (an extra investment on top, of course) can also help to manage usage. In terms of sizing the solar array, you can gain an idea of your requirements with the Energy Saving Trust’s solar panel calculator. According to the organisation, a typical 3.5kWp PV panel system (producing 3.5kW of electricity at peak efficiency) will cost around £7,000. Its research suggests this should reduce bills by between £140 and £340 a year. For a homeowner living in the middle of the UK, the Trust reckons it will take between 11 and 13 years to recoup the installation costs.

How Much Do I Save with My Own Solar PV System?

My own 3.04kWp, 16-panel installation, which was fitted in 2011 under the most generous Feed-In Tariff, took seven years to recoup its £10,000 installed cost. Last year, it generated 1,695kWh – which amounted to just over 70% of our household’s total annual electricity use of 2,333kWh (we’re unlikely to have used 100% of the solar supply, but do enjoy payments on it from our Feed-In Tariff). In the first year it was installed, the system produced 2,052kWh. The reduction is probably due to a combination of fewer sunny days and expected power output degradation. With these figures in mind, our solar PV system has generated an average of 1,873kWh per year.

Meanwhile, Ofgem suggests that harnessing sunlight could reduce the average UK household’s annual electricity consumption of 2,700kWh by at least a third. Broadly speaking, the further south you are located, the more efficient your panels will be. But it’s important to remember that each installation is completely unique, and electricity prices regularly change.

what to budget for solar panels

Who Should Install My Solar PV System?

Both your solar panel system and its installer should be registered under the Microgeneration Certification Scheme (MCS), as you’ll need an MCS certificate to qualify for energy providers’ SEG schemes. It is also essential to check and ensure that your installer is a member of either the Renewable Energy Consumer Code or the HIES Consumer Code. All three of these organisations list approved contractors across the UK. It’s advisable to obtain quotes from at least three different installers, including estimates of the panels’ outputs.

Solar PV panels that mimic roof tiles, like these examples from Solex, may allow you to obtain planning permission for arrays in conservation areas and on listed buildings

Installation should be easiest on a new, self build house, not least because scaffolding is likely to be already in position – plus you can easily opt for a discreet flush-mounted system that sits in line with the roof tiles. On an existing house, fitting a typical array can be a relatively simple matter of lifting roof tiles and securing the mounting structure to the rafters. The installer will first need to check that the roof is in good condition and able to support the desired number of panels.

It’s also worth checking if your installer will include bird proofing around the perimeter of the array. Pigeons tend to find the underside of PV panels an attractive nesting spot and their waste is caustic enough to corrode DC cabling. But their interest is unpredictable. My own panels seem unusually attractive, while my neighbour’s array, centimetres away, is spurned.

Do Solar Panels Require Any Maintenance?

Once installed, solar panels are virtually maintenance free and product warranties of up to 30 years are common. They do lose capacity over time, typically at a rate of around 0.5% to 0.9% per year, but will still produce useful power for up to 40 years. Inverters, however, typically have warranties of between five and 10 years and are likely to need replacing several times over the lifetime of your system.

Should I Pair my Solar PV System with Battery Storage?

A home battery system allows electricity produced by your solar panels to be stored for later use, typically in the evening. It can also store low-cost (night-rate) grid electricity to further optimise bills. A battery is most cost-effective for PV systems over 2.0kWp and owners who can’t make full use of their panels during the day.

A system’s battery and inverter are typically installed in a dry, well-ventilated garage or utility room, though never in attics as their weight and potential for overheating while charging may present a risk. Photo: Treadlighter

Battery costs can be close to the price of the PV panels themselves, however, which will extend the period required to recoup your initial investment. You will also need a separate inverter, unless your battery includes one, and a bi-directional smart meter, showing both electricity exported and imported from the grid. PV batteries are usually fitted indoors, but if space is tight then IP66 rated versions are also available that can be installed outside with well-ventilated weather protection, though never in direct sunlight.

guide to battery storage

An alternative to battery storage is a thermal store, like this washing machine-sized ZEB from Tepeo (tepeo.com), which can provide heating for both hot water and entire central heating systems

The best use of a battery system is with a Time-of-Use tariff, which charges different rates at different times of the day. These are available from major energy providers, including Ovo Energy, British Gas and E.ON. At the time of writing, the most generous is Octopus Energy’s Agile Octopus tariff which adjusts its pricing every 30 minutes.

A simpler alternative is to opt for a thermal rather than electrical battery. Here, both PV and cheap rate grid electricity are used to heat a highly insulated thermal store. Tepeo’s ZEB boiler uses a solid high-temperature core to provide both central heating and hot water.