FAQs – Solar Electric

I want to reduce my bills, but is Solar PV still a good investment?

Yes, our Solar PV systems are still earning our customers an average of 12-15% return on investment each year, for a standard 4kW system. That’s because your PV system earns money in three ways:-

  1. You’ll be paid for the electricity you generate whether you use use it or not
  2. You’ll be paid extra for the electricity you export to the national grid.
  3. The electricity you generate and use in your home saves money on your electric bill, even though you’ve already been paid for it! (We generally have to explain this 3rd point 2 or 3 times, as it seems too god to be true, but it is! And that’s why there are still so many PV systems being installed)

Also the income is tax-free and inflation linked. The Government backed feed-in tariff (FIT) income scheme continues for 20 years. After that you will continue to earn export income and save on your electricity bill for the life time of the system, which could be for an extra 10 or 20 years!.

I’m aware of the FIT scheme, as my neighbour has had a system for years, but the Government has reduced the FIT rate, so I won’t make as much as my neighbour, is it worth it?

Again yes! The FIT has been reduced in line with the number of systems that have been installed, which has caused massive global price drops in Solar Panels, Inverters and system components.

This means that the average cost of a 4kW system has dropped from an average of £12,000 to £5000, so the investment rate of return has stayed about the same.

As system prices fall the Government will continue to reduce the FIT for new installations. However, once your system is registered on the FIT scheme, your tariff will be locked in for the full 20 years. The only way your tariff will change is if it increases along with inflation, which it is tied into.

How does solar electricity work?

Solar electricity utilizes the sun’s energy to generate clean, green electricity. Solar Photovoltaic (PV) modules contain photovoltaic cells which are engineered to convert sunlight directly into electricity.

Most Solar PV systems are grid connected; this enables the solar generated electricity to be fed directly into a building’s existing mains supply. Power generated from a Solar PV system reduces the amount of electricity that your household imports from the grid subsequently cutting the cost of your bills. Any excess ‘green’ electricity not used by your household is fed back into the grid and in effect purchased by your energy supplier in the form of feed-in-tariff (FIT) payments. (For an in-depth breakdown of how the FIT works see the FIT example on our website.)

Solar PV system’s consist of three main elements:

  • an array of solar PV modules
  • an inverter(s)
  • cables, display and switchgear


Image taken from: http://www.caplor.co.uk/talk-to-us/how-works/how-solar-pv-works/

The inverter is an electronic device that converts the solar electricity (DC) produced by the solar panels into AC electricity with the same voltage and frequency as the mains supply. The inverter is also outfitted with various safety features, constantly monitoring the grid and switching off in the event of a fault in the mains supply.

The output of the inverter goes directly into the building’s fuse box – feeding solar electricity into the building’s electricity supply which means you will not have to purchase as much electricity from your supplier, making your household more energy efficient whilst cutting bills.

Do PV systems work in the UK?

Yes!!! Solar PV systems work very effectively in the UK, though the electricity produced is obviously lower than in sunnier countries. There are now thousands of systems throughout the UK, where customers are reaping the benefits of their solar electric system AND claiming a tax free income from the Feed In Tariff.

How do I get an EPC, to prove if we can get the higher EPC tariff?

Your home needs to have an Energy Performance Certificate (EPC) with an energy efficiency rating of band D or higher to benefit from the highest level of FIT. We have our own in-house assessor’s so we can easily arrange a survey for you. Even if you are currently an E rating, your planned Solar PV system will improve your rating and can be used to show that with PV panels your house is a D, so you will still get the higher rate.

How is the solar electricity used?

The output from a grid connected PV system is fed directly into the households existing circuits, usually through the main distribution board. Apart from lower electric bills there is no difference between the electricity generated by the solar panels and the electricity bought from your supplier.

What happens if the system generates more than the building is using?

If the Solar PV system is generating more electricity than your household is currently using, all excess is exported to the grid. Export occurs automatically and can be measured (and income collected) using an “export meter”.

How long will my PV system last?

Most solar panels come with a 25-30 year guarantee and inverters generally have a 5-20 year guarantee depending on the manufacturer. Sustainable Energy provides a 10 year customer workmanship warranty on all its installations. There are PV systems still working after 40 years, so systems should last much longer than the 20 or 25 year FIT schemes.

What range of roof pitch is acceptable?

The ideal roof pitch is between 30 and 45 degrees from horizontal. However, pitches between 5 and 60 degrees will result in less than 10% losses for a south facing roof. A free site survey carried out by Sustainable Energy can provide specific output and return-on-investment estimates.

We would like a PV system, but have heard they are very expensive and will take years to repay?

We install systems to suit our client’s needs. So we will design a system to suit your budget. We can now install a typical 4kW system with polycrystalline panels from £4500. On a good, south facing roof, this would equate to an annual return of £835, which could pay for itself in 5 years.

Do I need planning permission?

Generally PV systems are classes as a permitted development. Listed buildings and sites in AONB would need to seek advice; however planners look very favourably on PV systems and are under pressure to accept them.

Do PV systems need regular maintenance or servicing?

There are few moving parts on a PV system, which means that there is very little to wear out. However, the MCS guide and manufacturers recommend that systems are serviced to ensure that connections are sound and roof fixings are secure. Also in some locations a build of dirt on the panels can reduce output, so we would recommend them being cleaned.

What is a Solar PV panel?

Photovoltaic panels are made up of a large group of PV cells that convert light into electricity. A standard PV cell contains a wafer of silicon that has been manufactured with a “p-n junction” inside. This junction creates a border between the “p type” and the “n type” silicon. Light frees these electrons inside the silicon and they are then picked up by the electric field of the p-n junction. Small metal contacts running through the cell will then take the electric current that has been produced to a central point on the back of the panel. The cells are compressed between a sheet of glass and a laminated backing sheet, which is generally fixed within a rigid aluminium frame. The frames were traditionally silver, but are increasingly anodised black to give are more aesthetically pleasing look.

What are monocrystalline and polycrystalline cells?

Monocrystalline and Polycrystalline describe the kind of silicon that is used to create the PV cell. Polycrystalline cells use multi-crystalline silicon that is cheaper to produce as it is created from a patchwork of individual crystals. Consequently, this makes it slightly less efficient than the monocrystalline cell. The Monocrystalline cells use a wafer cut from single crystal silicon, usually cut from an ingot. Monocrystalline cells are usually identical in appearance however the polycrystalline cells look slightly different because of the patchwork of individual crystals.

How is a system sized?

Solar PV systems are modular so therefore they can be almost any size necessary. The size of the PV system is usually dependent on the available roof space, the clients budget or is designed to hit a certain percentage of a buildings electricity needs.