Understanding the Lifetime Costs of Solar Panels

Paul Taylor
With a 10% “guaranteed” return on investment, fitting solar photovoltaic panels to the roofs of domestic properties has to be a very attractive investment for anyone with the 10k or so needed for a typical system.

Solar photovoltaics (PV) are a well proven technology, which has been shown to be long lived, but we are still a long way from grid parity, i.e. where the cost of electricity from solar equals that which you can buy from electricity companies. To encourage uptake the Government has introduced the Feed in Tariff (FIT) scheme, giving an index linked bonus designed to give an attractive financial return to investors.

The FIT scheme has seen an explosion in the number of companies offering to fit solar systems, and has also seen solar systems moving from being a fringe product to one that is almost sold as a commodity on lowest first price. The market has been likened by some to the double glazing market, with often costlier nationals competing against local companies with lower overheads, and many companies merely acting as “front men” for sub-contractors – no wonder the average person is confused, especially given the very short track records of some companies. Many companies on the Microgeneration Certificiation Scheme (MCS) list have less than two years experience, and an ongoing question is how many will still be around in 25 years? Sadly many householders buy on lowest first price, simply because this is the only comparison that they can make.

For such a long term investment, reliability is key, and so we would advise on reducing your risk by looking at well known brands. Warranties are essential, with a 25 year performance guarantee now being standard for PV panels – but the detail of the warranties needs careful consideration as it is far from an “as new” warranty, with a fall off in performance of up to 20% being typically warrantied. You should also allow for replacing the inverter every 10-15 years, likely to cost around £1,000 a time. And finally you should budget for occasional cleaning of the panels and for electrical testing. When you factor these hidden costs in, the return on investment will fall – so always ask a supplier for a typical real life rate of return.

All MCS registered suppliers have to quote typical outputs to the building standard assessment procedure (SAP). But this is based on a UK average insolation, and only has a simplistic approach to the key issue of panel shading. If your roof layout is not simple, then more detailed calculations should be sought.

For solar panels, there is a huge variety that may not be offered by all suppliers. Typically, for domestic homes, the choice is simplistically between black or blue panels, and then there is a choice of mounting system colour – it doesn’t have to be bare aluminium – other colours are available and may look much nicer. It is up to the supplier to be happy that the roof structure is sound, if there is any doubt then they need to call for a structural survey to check it can withstand the additional loading.

Planning permission is no longer a serious issue unless the property is a listed building or is in a conservation area, but this is far from a “no go”, often just meaning a delay while permission is sought.

That said, while most people are happy with the appearance of a well designed system, there are some “ugly” systems around that just do not integrate well with the building, and here there may be an impact on the value of the house. Perhaps the colours are wrong, the panel layout cluttered, or the panel colour or form destroys the existing lines of a building. Solar roof tiles can be used in place of ordinary roof tiles to give a fully integrated look although these systems are more expensive.

Things rarely go wrong, but when they do, there is an immediate cost of scaffolding to reach the roof, typically £500 for a domestic property. This is assuming that it is straight forward to position scaffolding; if access is not straightforward, for example if there is a large conservatory that has to be bridged, then the costs will be greater.

To make the most of the value of electricity generated, the occupier needs to be around during the brightest part of the day to make use of it, and so they need to be prepared to alter their behaviour to make the very most of it.

Whilst the FIT gives close to a 10% return on investment for schemes registered by 31st March 2012. The FIT for the period following this is likely to be much less generous. We hope that in the rush to install solar PV, householders make decisions based on a full understanding of the lifetime costs of ownership, and of the technology options that are open to them. Sadly, our experience is that this is not always the case. While the individual householder may struggle to fully understand the considerations, for anyone with a responsibility for designing systems for larger developments, independent advice on PV will not only point the way to the best system, but give the confidence that it will still be working to satisfaction throughout its life.