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Green Technology: Solar PV for Electricity
As part of our comprehensive guide covering all aspects of green technology, we look at Solar Photovoltaic Panels that are used to produce electricity and examine the benefits and system requirements.
How do I know what size kit to buy? They all seem to have different ratings in kW. What does this actually mean?
Most people install a system between 2-3kWp, generating between 1,700-2,500 kWh (units) per annum. This is not equivalent to total needs of a typical house, which the EST (Energy Saving Trust) estimates to be 3,300kWh. However, it is not essential to provide all of your home’s electricity via solar PV (photovoltaic). The best Feedin Tariff rate is available for systems up to 4kWp.
Kilowatt peak (kWp) refers to the value of power generated by a solar tile or panel system under full solar radiation (under set Standard Test Conditions). Solar radiation of 1,000W/m2 is used to define standard conditions. In the UK, 1kWp of solar will generate roughly 850 kilowatt hours (kWh) per year. Typically, the full installation will cost between £4,500-6,000 per kWp. Most homeowners install a system of between 2-3kWp, and expected lifetime is up to 40 years.
How do PV panels actually work?
The panels produce energy from daylight, not direct sunlight, so they still produce energy on cloudy or overcast days. An inverter converts the electricity from direct to alternating current, which can be used in the home.
How do I choose between different PV panels?
Firstly, it depends on whether you want the panels integrated into the roof shape (perfect if you are reroofing) or want them as a retrofit roof-mounted installation. Make your decision based on the power output (it should be guaranteed for up to 25 years) and look for a system that requires no on-roof maintenance. Look for installers that are accredited under the Microgeneration Certification Scheme (MCS) — your kit is only eligible for income under the Feed-in Tariff scheme if this is the case.
Saving Energy, Earning Money
PV installation pays dividends.
Patrick and Frances Colquhoun own a 1940s detached house in Cambridge and installed a Solarcentury Sunstation 2.15kW PV system in October 2009 — similar to the one shown. It is estimated that it will produce 1,600kWh per year (reduced from the usual 1,827kWh owing to its south-easterly orientation and the fact that the site is part-shaded).
The couple will find themselves enjoying the best of both incentive schemes — they received a £2,500 grant under the Government’s Low Carbon Buildings scheme, which reduced the cost to £9,848 including installation, and will also enjoy the benefit of Feed-in Tariffs when they are introduced in April. “We have seen substantial bill reductions already, and we have also done this for investment purposes — we’re expecting between 8-9% annual return.” They also hope to enjoy an annual revenue of £710 from the electricity the system generates (plus an extra £26 from electricity exported) and it will cut £112 a year off their electricity bills — this gives a payback period of 11 years. solarcentury.co.uk.
Feed-in Tariffs and PV
Solar PV attracts the highest tariff (price paid per kWh) of all the electricity-generating renewables to benefit under the Feed-in Tariff scheme, which came into effect in April 2010 (see homebuilding.co.uk/green).
Domestic-sized units (under 4kW) enjoy 36.1p/unit in a new build installation which goes up to 41.3p/unit if you fit it in an existing dwelling (defined as ‘one already occupied’).
H&R suggests that self-builders calculate the potential benefits of installing a PV system after a completion certificate is issued. Bear in mind your panel will be zero-rated for VAT if fitted ‘new’.
Our View |
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The equation for PV has been transformed by the introduction of FiTs — meaning the storage issue is dealt with. Capital costs are falling too. |
Have your say on green technology in the Homebuilding Discussion Forum
More Green Technology:
Further reading
- Feed-in Tariffs: How to Make Money By Installing Renewables
- Self-sufficiency: A Green Dream or Reality?
- The A-Z of Green Homes
- Author
- Jason Orme and Tim Pullen
- Issue date:
- June 2010
Useful links
- Energy Saving Trust
- Advice and information
- Solarcentury
- Solar PV
Why does HR recommend waiting till a completion certificat is issued before calculating the potential benefits? I would have thought this should be done at the planning stage and the pv panels built into the roof, saving money on tiles and labour. Also why not store electricity in batteries and save the cost of connecting to the grid, the house I am living in now I was charged £3,000 because they had to come over the road and down the pavement. A small diesel genny could be on standby for the times when insufficient energy was generated.
In principle it is good to see new incentives to promote the use of renewables but they need to be thoroughly thought through, holistic in concept and fair in application.
The new legislation on FITs which came into operation on 1 April is a clear case in point. I was one of the "PV pioneers" - installing systems to use "free" energy out of commitment rather than economic gain but before the magic date of July 16, 2009. To be fair to Scottish and Southern Energy who clearly recognise the need for more renewables, they have increased the payment for my exported energy from 15 to 28.5p over the last 18 months. I run a pretty efficient domestic property and we make considerable efforts to reduce energy use and to "save" energy so on the "old" scheme there was a real fiscal incentive to export as much of the energy we generate as possible (our export averaging around 2/3rds of what we produce).
Under the new system of tariffs I now get paid for everything I produce but only at the rate of 9p because I received £2500 from a LCBP grant (relatively modest for an almost £16,000 installation). It appears the same rules apply to those who received a 50% grant for their "Clear Skies" installations (to a maximum of £30,000).
I'm not sure I or any of the other pioneers will now receive anything for what we export. We might just receive 3p but I am awaiting a response from my electricity supplier to confirm this; what is the incentive to save energy on this new system (other than personal commitment)? Why are the Government seemingly penalising a small number of pioneer installers (who dug deep into their pockets out of commitment) for what must be a tiny cost saving. In fact the cost of rectifying this isparity will be minimal since relatively few projects will have fallen into this trap; however to do so will help restore confidence that projects will not in future be sabotaged by arbitrary regulatory change.
We have a similar problem with the 6.5kW installation I was involved with on our church roof in Cheltenham. The business case we made to our donors - particularly church council - for this installation has been totally destroyed by the "new" system. We are exporting significant quantities of 100% green energy to the national grid and it looks as though we will receive absolutely nothing for so-doing; this is no way to encourage energy conservation.
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