The Complete UK Solar Panels Guide

What’s in the Guide

• 1. What are solar panels and how do they work?
  • Parts of a Solar PV System
  • The Solar Cells
  • Types of Solar Panels
  • The Inverter
  • On and Off Grid Solar Systems
• 2. Is my home suitable for solar panels?
  • Where do you live?
  • Which way does your home face?
  • How pitched is your roof?
  • How strong is your roof?
  • How much external space do you have?
  • How much internal space do you have?
  • Do you live in the woods?
• 3. Solar panels and planning permission in the UK
• 4. Solar panel costs and prices
  • The Cost of Solar Panels
  • Free Solar Panels
  • Price Versus Quality
• 5. How much could you save?
• 6. Are Solar panels worth it?
  • Financial benefits
  • Property benefits
  • What about maintenance?
  • Environmental benefits
• 7. Choosing a Solar Panel Installer

What are solar panels and how do they work?

We all know solar panels convert the energy from the sun into electricity for our homes, but how do solar panels actually work? and what are the parts we need for our solar panel system?

Parts of a Solar PV System

• Solar panels: The individual photovoltaic panels are made up of groups of solar ‘cells’. The cells are made from a special material called a semiconductor and are grouped together to form a panel or module. The modules are then connected together in a group, known as a solar ‘array’.
• The inverter: The power that is generated by the solar array is direct current (DC). Homes work on the safer and more reliable alternating current (AC) system, so an inverter is used to convert the DC into useable AC for the home.
• The fuse box: From the inverter, current travels to the fuse box of the home in order to be distributed around the home and used by our appliances. This ensures the current is safe and our home is protected from any power surges or problems.
• The meter: Depending on the type of PV system installed, a range of meter options are available. For new installations, a meter will be installed to measure not only how much energy is produced for the home, but also how much excess energy is sent back into the grid, allowing the householder to claim additional payment under the Feed in Tariff (FiT) scheme. Some installations may also have display units to let you know what is being generated right now and other details of the system performance.

The Solar Cells

All solar cells are made from a semiconductor material, the most common being silicon. These materials have special chemical properties that are at the heart of the solar energy generation. An atom of silicon has 14 electrons arranged over three shells. The first two shells are full, with two and eight electrons each, but the final shell is only half full, with just 4 electrons. This means the atoms are inclined to ‘hold hands’ with neighbouring atoms, creating what is known as a ‘crystalline’ structure.

When energy is added to pure silicon, it causes some of these electrons to break their bonds and leave their atoms. Known as ‘free carriers’ these electrons wander around the crystalline structure, all charged up with energy, looking for a new place to bond. However, in pure silicon there are so few of these free carriers, it turns out to be a rather poor conductor of electricity.

To make a solar cell efficient, it must have an impurity added. Far from being a bad thing, these impurities are what turn a useless slab of silicon into a highly efficient electricity generating technology. Phosphorous is often used to dope silicon, mainly because its chemical composition gives it five orbiting electrons. This means it has four ‘hands’ to hold in a bond with the silicon atoms, but will still have one ‘spare hand’ that is not bonded to anything. This makes it a lot easier to knock one of the electrons out of its orbit, thereby making the silicon a much better conductor of energy. Because of the high number of free electrons in this type of panel, this is known as ‘N-type’ (negative type) silicon.

But, this is not where the science bit ends! On the other side of a solar cell, silicon is mixed with atoms of boron, an element that has only three electrons in its outer shell. When energy is applied to this type of silicon, there are ‘holes’ left in the structure where there are not enough electrons. This gives the panel a positive charge, creating what is known as ‘P-type’ silicon.

When you put these two, oppositely charged pieces of silicon together, the free carriers from the N side rush to fill the holes in the P side. This creates an electrical field and is the basis of PV panel technology. When light from the sun, carried as ‘photons’ hits the panel, the electron pairs are disrupted. The movement of electrons provides a current, and the electrical field of the cell provides the voltage; voltage plus current = power.

Types of Solar Panels

As previously discussed, the most common material for solar PV panels is silicon. However, this silicon can be presented in a number of different formats which will affect the performance, cost and efficiency of your solar system.

• Monocrystalline: Have slightly higher efficiency although polycrystalline types are catching up. Monocrystalline panels are more expensive than polycrystalline alternatives and whether the difference in performance (and look) is worth the extra money will depend on preference and the needs of the individual install. Often the quality and reliability of the manufacturer will be more important than the technology.
• Polycrystalline: The most common type of cells used, provides 14 – 16 per cent efficiency at a reasonable cost.
• Thin film / amorphous: Has the benefit of being able to be fitted to curved surfaces and a very thin finish but comes at a cost of efficiency. Typical efficiency is 5 – 7% but does work well in diffuse light conditions.
• Hybrid: Hybrid panels use a thin layer of amorphous film behind the monocrystalline cells, extracting additional energy from the sunlight and resulting in a more efficient system. These are, however, very much more expensive than any other type so generally not cost efficient for the majority of householders.

The Inverter

Without an inverter, all this power that is being generated by our solar cells would be useless. The inverter assumes the task of converting this DC power into useful and safe AC power for the home. The downside of this is that the inverter for your system will also require some power to operate, so choosing an efficient type of inverter is essential. Modern inverters will only consume around 4 – 8 per cent of the generated energy themselves, leaving a good 92 – 96 per cent of the energy for your use.

On and Off Grid Solar Systems

With any solar system, there is the question of whether you will connect into the grid or set up a standalone system.

• Grid connected systems are the typical type for most needs and make use of the existing mains grid to displace any excess energy. If the panels do not produce enough power, the grid will do the rest.
• Off grid systems are far less common but are used sometimes for agricultural or very rural properties where there is no grid connection present. With this type of system, the power generated by the panels will be stored in deep cycle rechargeable batteries for use later on.

Image Credits:
http://www.flickr.com/photos/61485457@N06/5594991976/ CC BY-NC-SA 2.0
http://www.flickr.com/photos/86335404@N00/2223909169/ CC BY-NC-ND 2.0

Is my home suitable for solar panels?

Solar energy is a popular choice for households looking to invest some cash and cushion themselves from the regular price hikes we all see in our energy bills. With the Feed in Tariff (FIT) available for solar PV, the economic viability of solar technology is looking good, and a worthwhile place to invest your cash.

But before you rush out and sign up with the first installer who comes along, it is worth doing a bit of a personal check to see if your home is suitable for solar. Although most installers will only recommend solar if they think you are going to get a substantial benefit from it, there is no harm doing your homework first and making sure you understand what to expect.

Sarah / CC BY-NC-ND 2.0

Where do you live?

You might have heard that living north of the Midlands means you cannot benefit from solar, but this is fundamentally untrue. Because solar PV requires only ambient light to work, you can still gain significant benefits from the technology whether you live in Lands’ End or John O’Groats.

However, there is a difference in daylight hours north to south, which should be taken into account when deciding if solar is right for you. Reduced daylight hours and lower levels of solar radiation mean solar may be less efficient in the far north of Scotland. Achieving a return on your investment can take slightly longer but it is very much still an option.

Which way does your home face?

The orientation of your roof is very important in determining the amount of sunshine you receive during the day. The closer your roof is to a southerly orientation, the more efficiently your system will work. Again, that doesn’t mean that if you are in a house which has a west to east facing roof you can’t have solar; just that you need to account for this in your calculations.

How pitched is your roof?

The angle of your pitch is another important factor in the efficiency of your panels, but unlike orientation can be rather difficult to measure yourself. The ideal pitch will be between 30 – 45 degrees, but you can still expect good performance from pitches as shallow as 15 degrees or as steep as 50. If you plan to mount your panels on a flat roof, your installer will often be able to use a mounting frame to angle your panel at the perfect pitch.

How strong is your roof?

Solar panels in themselves are not particularly heavy, but if you are considering photovoltaics, then a whole solar array and the mounting frames used can weigh around 275kg. The majority of modern homes will have no issue in supporting this weight, but make sure your installer conducts an integrity survey to be absolutely sure.

For solar thermal, you’ll only need around 4 square metres of unobstructed space to mount the panel. If you are considering PV, it is closer to 10 square metres, about the size of a car parking space. For most homes this won’t be an issue, but check for vents and skylights you might have forgotten about to make sure you have enough space.

How much external space do you have?

For solar PV, you’ll need around 10 square metres of unobstructed roof space to mount a meaningful array. This is around the size of a typical car parking space. For most homes, this won’t be an issue, but do check for vents and skylights you might have forgotten about to make sure you have enough space.

How much internal space do you have?

The internal space requirement for a PV system is minimal, as the only bulky piece of internal equipment is the inverter. This requires around a metre squared of space, which can normally be accommodated in the loft without major problems. However, if you have a loft conversion or dormer bedrooms, make sure you’ve thought through where you plan to place this equipment.

Do you live in the woods?

It might sound like a silly question, but shading of any type can adversely affect the performance of your solar system. When it comes to PV, if any portion of the array is shaded, the efficiency of the entire system is drastically reduced. Don’t forget that the angle of the sunlight changes over the year, so ask your installer to do a seasonal variation model to see if your roof becomes shaded in the winter.

If, after asking yourself these questions, you think your home might be suitable for solar, it’s time to call in the installers to conduct more detailed investigations. Always choose an installer who is a member of a professional body such as the Solar Trade Association, and they will be able to conduct additional tests and surveys to establish how suitable your house is for PV.

Solar panels and planning permission?

In the majority of cases, solar PV is a permitted development. This means you don’t need to apply for planning permission or to consult with your local authority before going ahead with the work. However, to be safe rather than sorry, it can be a good idea to talk to your local authority before signing up, just to make sure you are not required to seek permission.

In some cases, planning permission may need to be sought. This is usually if you are living in a listed building or in a conservation area. You’ll find more guidance on this on our solar panel planning permission page.

Solar panel costs and pricing

With the combined benefits of a reduction in energy bills and sustainable green energy, more and more households are starting to seriously consider generating their own electricity. But how much money do you need to invest to start taking advantage of solar energy

The Cost of Solar Panels

The entire cost of your system will depend on a number of factors, and we always recommend you get several comparative quotes before making your decision. The things that influence the cost of your solar system include:

• The size of the system installed (measured in kWp)
• The manufacturer and specifications of panels
• The manufacturer and specifications of the inverter
• The expertise and location of the installer
• Any additional equipment or labour needed to access or install your system

As a general rule, a domestic system will be around 4kWp in size. In today’s market, this will cost in the region of £5,000 to £8,000 to install, although it could be significantly more if you are looking for specialist technology. Solar tiles, for instance, can be a great way to integrate your solar system with a new roof for your home, but you can expect to pay around double the normal cost for this type of system. A solar panel installer will usually need to do a site visit to assess the suitability of your site, your expected returns and to accurately quote for your specific circumstances.

The cost of solar has fallen over the years as demand grew and competition was stimulated. Research carried out by Green Business Watch in 2019 showed that the median cost of solar PV has reduced from around £20,000 in 2010 to £10,252 in 2012 and £6,856 in 2019. These cost reductions seem to have leveled off in the last few years due to Government changes to subsidies and their negative impact on the market. With the lower costs and increased savings as electricity bills rise, well sited solar has continued to offer a return, even as subsidies decrease.

Free Solar Panels

If you want to install solar but are concerned about the cost, you will find some companies offering to install your panels for free in return for your FIT payments. Although, these offers are less common than they once were. If you are able to buy, then buying should always be your first choice option, but for those unable to raise the capital then free solar may be something to consider. Free solar panels work for people who:

• Don’t have money to invest and are unable, or unwilling, to get a loan
• Want to make savings on their energy bills
• Are concerned about ongoing maintenance costs – maintenance is usually included with free solar panel offers
• Are keen to mitigate the impact of energy price rises

For some people, there will be a benefit to getting solar panels sooner rather than later by taking up a ‘free solar’ offer, but we urge these people to read the fine print. Finding out how long the company will be borrowing your roof space for, who will own the panels at the end of the loan period and what happens if you want to move or sell your home are all questions to be answered before you jump on in.

Price Versus Quality

As well as considering the cost of the panels in general, it’s important that you are confident about the quality of panel you are purchasing and confident about your installer. As with most markets, there is some degree of getting what you pay for in terms of quality. Talk to your installer company about the panels they are recommending, and ask for the reasons that they chose these panels. Find out about warranties for the panels, the inverter, and the workmanship.

Be wary of installers who don’t have comprehensive and extensive answers to such questions. You don’t want to get lumped with a poor-quality panel or inverter just because the installer got a great supply chain deal or got a container load cheap. Ensure you are confident in your installer’s ability to assess your situation and to design the best system for your needs, rather than just the cheapest.

How much could you save

Solar PV is maturing as a market in the UK and the cost of installation is continuing to fall. However, as the cost of the technology has fallen, so too has government subsidy via the Feed in Tariff (FiT), so where do we stand right now? Just how much can you save with solar PV for your home?

Here are some quick figures for a 4kW installation at the September 2018 Feed in Tariff rate of 3.93 p/kWh, using an average tariff rate for supplied electricity and the standard 5.24 p/kWh for exported energy.

In line with previous estimates, we have assumed a load factor of 850kWh/kW/year for well sited solar PV, meaning that the system will generate 850kWh per year for every kW of peak capacity.

A 4kW system generates 3,400kWh per year. Electricity use is assumed to be 50% on-site with 50% exported to the grid and electricity cost savings are calculated with an average price per unit of 0.16p. The 3.93 p/kWh FiT rate applies for installations with eligibility dates between 1st July 2018 and 30th September 2018

Feed in Tariffs have fallen in the last year, lowering income but the cost of domestic electricity has resumed it’s long term rising trend, which increases solar savings.

A 4kW solar panel system still has potential to generate considerable income and savings of around £500 annually. Interestingly, the majority of this return is now from savings on electricity rather than income from the government’s Feed in Tariff. The Feed in Tariff payments are guaranteed for the 20 year term of the scheme and index linked to rise with inflation. Electricity prices are also likely to continue their long term rising trend and both of these factors should mean increasing returns over time.

Are Solar panels worth it?

The numbers stack up for solar; it looks like a good investment. But does this tell us the whole story, and what else should we be thinking about before investing in this popular technology?

Financial benefits

Let’s say you bought the 4kW solar system that we illustrated above, and it cost you about an average amount of £6,500. On this investment, through savings and FiT payments, you’ll be earning around a 7.42 per cent return every year. With UK interest rates at an all-time low, averaging just 1.23 per cent over 2016, investing in solar PV far outstrips the return you’d get on your money in the bank, so it makes great economic sense if you have cash to invest.

However, this calculation only works if you have money to invest up front. If you are looking at getting a loan, remortgaging or participating in a rent-a-roof a.k.a. ‘free solar’ scheme to get your panels, you won’t get as much benefit from your investment. Depending on the rate you get on your loan or the deal you strike for your free panels, you could even end up losing out. Proceed with caution if you don’t have the cash to invest outright.

Property benefits

Some homeowners think that by installing solar PV on their property, they can increase the value, much like adding a conservatory or converting the loft. Unfortunately, although this makes perfect sense, it is yet to play out like this. Which? surveyed a number of estate agents in the UK and found that:

• Only 8 per cent thought it would increase the value of the home
• 17 per cent said it actually decreased the property value
• 67 per cent said it made no difference at all

As time presses on and people become more familiar with solar and the benefits it can bring, perhaps property values will start to be positively affected. For now, however, this is not a good reason to invest in solar panels, and you’re more likely to feel the benefits of your investment if you plan to live in the house for many years to come.

What about maintenance?

Solar PV doesn’t require much maintenance at all, thanks to there being no moving parts. However, you might need to factor in a professional cleaning, as dirt and debris will significantly affect the efficiency of your panels. You should also factor in a replacement inverter, as these tend to decrease in efficiency over the course of many years.

The panels themselves tend to last and last; if something needs replacing, it’s usually the inverter unit. Crystalline solar panels will degrade in output at around 1 per cent per year, which is why most manufacturers limit the lifespan warranty to 20 years. Panels with shorter warranties than this may not be the best quality, so talk to your installer to find out why.

Environmental benefits

Of course, choosing solar PV is not all about return on investments, adding value to your home and so on. A great deal of making this choice is about doing the ‘right thing’ for the future of our planet.

Excess carbon dioxide in our atmosphere is causing changes to our climate, and the UK has target to reduce carbon emissions by 80 per cent by the year 2050. By installing solar panels, you’ll be reducing your fossil fuel use and thereby helping the nation edge closer to this target. You, personally, will reduce your carbon footprint by around 1.5 to 2 tonnes every year, that’s around 20 per cent of your personal footprint!

As well as reducing CO2, installing solar PV will help to reduce our demand on fossil fuels overall. This means less demand for dirty power stations, less impetus to build more nuclear plants and improved air quality for everyone. As fossil fuels become scarcer, which they inevitably will, those who cannot generate their own energy will be at the mercy of fuel suppliers, whereas those will renewable technologies in their homes can hope to mitigate the impact of future price rises.

Choosing a solar panel installer

Buying solar PV for your home is a major investment, so it’s important to have the right people around you to get the job done well. As the popularity of solar has risen, so too has the number of companies claiming to be cheaper, better, faster than their competition.

For this reason, it’s important to choose a solar installer who is accredited, referenced, reputable and trustworthy, so you don’t’ end up with a bunch of cowboys working on your roof. See our article for more tips on how to select the right solar PV installer for your home.

We recommend getting at least three quotes from good solar installer companies, so that you can ensure you are getting the right product at the right price. We’ve put together a comprehensive database of qualified solar installers around the UK, so make it easy for you to find, select and contact an installation company near you. Find your perfect solar installer here.