A year of solar power: the verdict

15th August 2011


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Last year, Dr Mark Everard reported on the installation of 17 photovoltaic panels on his house in North Wiltshire. Now, one year on, how has the system performed?

Our photovoltaic (PV) system was installed on 22 May 2010 and, as April 2011 progressed, we grew obsessed with seeing if we’d reach a largely arbitrary, but nevertheless nicely rounded, total of three thousand kiloWatt hours (kWh) in the first year.

That milestone was passed on 10 May, and by the 12-month anniversary on 22 May, the panels had generated 3,165 kWh, averting 1.7 tonnes of CO2 emissions. That means the 17-panel system has performed 25% above projected generation over its first year.

Performance has varied on a daily basis, from three successive lows of 0kWh generated, when the panels were covered in snow, to a “record high” of around 22kWh. Output closely tracked weather, day length and moment-by-moment changes in sunlight. On a clear day, output was a beautifully symmetrical “bell curve” on the read-out, but it turned rather “spikey” when clouds scudded across the sky.

Financial performance

Our motivation for installing the PV system was almost entirely values-based, but it certainly had to pay its way. People in the industry tell me that most investments in home-scale PV are not justified on sustainability grounds but because homeowners with spare cash anticipate better financial returns than from currently low bank or building society interest rates. But did it stack up financially for us in the first year? Well, the bill for the quarter ending June 2011 recorded a credit of £42.34.

More importantly, a rosy picture has emerged across the year. Allowing for some assumptions, the bottom line for the first year was a healthy overall benefit of £1,604.94.

This comprises feed-in tariff (FIT) payments over the year of £1,332.82, covering payments for energy generated, whether consumed or not, in addition to 3p per unit of energy deemed to be fed into the national grid, as well as a £272.12 saving on electricity consumption – compared with the previous year’s bills.

This shortens the theoretical payback period to around nine years – against a projected 11 plus years – over which there is a return on investment of nearly 11.5%, and beyond which there is pure profit.

Of course, there may eventually be a small drop-off in system performance with age. But, with energy companies recently announcing significant increases in electricity prices, the financial savings are likely to increase further.

The jury is still out over a couple of issues, however. The first concerns locking yourself into a technology for 25 years.

How will the PV panels look and perform by 2036? The safety net here is that PV installations are guaranteed, and the FIT is contracted for 25 years. So, regardless of the emergence of shinier, newer and more efficient technologies in future, the benefits are known.

The impact of a PV system on the value of a property is also currently largely untested. Some claim that PV systems can only add value as new occupiers become eligible to receive FIT payments. Others suggest that the value of a property to prospective buyers who do not like PV systems will be diminished. Opinions vary, but clear evidence is yet to emerge.

A positive glow

Notwithstanding these questions, the balance of benefits of PV installation is otherwise pretty clear. We are saving carbon emissions, becoming a net supplier of electricity, benefitting financially from it, promoting an industry with a future, spreading the learning and making physical and visible our commitment to sustainable development.

Unfortunately, the government’s fast-track review of the FIT for bigger plants (50kW and over) has stifled investment in large-scale solar and other renewable-energy technologies by the agricultural sector and municipalities, such as Cornwall County Council.

The silver lining to this dark cloud is that domestic-scale tariffs continue unchanged. Not only has the FIT remained in place for domestic PV installations but promises by the government to keep it index-linked have been honoured.

Last financial year, the FIT for domestic PV stood at 41.3p per unit. This increased from 1 April 2011 to 44.3p, in line with the retail prices index rise of 4.8%. Annual FIT payments for a typical 3kW peak system should rise by around £50 as a result.

The FIT has in fact been a great success in driving uptake of renewable-energy systems. Official figures reveal that 28,608 photovoltaic systems, out of a total of 30,263 renewable-energy installations (also including hydropower, wind, micro-CHP and anaerobic digestion), were registered within the first financial year of the scheme, which started in April 2010.

But so much more could have been achieved in the UK. Germany’s solar sector now employs 133,000 people and is worth €10 billion a year. It has installed capacity of 17,000MW, with more coming on stream under a national strategy to phase out coal and nuclear generation in a climate-challenged, post-Fukushima – the site of the recent nuclear disaster – world.

Meanwhile, the UK’s paltry 75MW of installed PV capacity and the backtracking on support for larger systems signals that it is unlikely to make an equivalent quantum leap, with all the benefits this would bring.

Busting common myths

Dr Mark Everard’s photovoltaic (PV) system and his earlier articles for the environmentalist promote the sustainability virtues of PV, but the technology continues to be accompanied by myths. Here he tackles the common ones.

  • Does it heat water? PV systems convert light (photo-) into electricity (-voltaic), whereas solar thermal systems trap heat, warming water running through them. These are different systems entirely, although some hybrid products are just entering the market.
  • Isn’t it really complex, and doesn’t it require rewiring? No, PV panels attach to metal rails on the roof, their direct current output is routed to an inverter unit in the loft which converts this to alternating current, and this goes via a meter into a spare gangway in a normal domestic fusebox. No other wiring is required.
  • Isn’t it really complicated to use? Not at all. A clever (also solar-powered) box sits on the windowsill and receives wireless signals from the generation meter, providing instantaneous, daily and month-long read-out data.
  • This type of new technology is bound to go wrong, isn’t it? PV has been around a long time, and is the basis of a mature and substantial global industry. The technology is not only reliable and proven, but comes with long warranties.
  • Why do planners tell me that I can’t have them on my house? Some planners remain ignorant of the law or else are just plain obstructive. My house is in a conservation area – an often cited obstruction – but has a PV system that was installed quite legally, even though planners initially told me it could not be installed. Part 40 of the General Permitted Development Order allows them to be installed.
  • What if the government scraps feed-in tariff (FIT) payments, the main economic driver? It may eventually do so for new entrants, as we are seeing for large-scale systems, but a registered PV system constitutes a 25-year contract with payments not only guaranteed but index-linked.
  • A company has offered to install panels for free and I get to keep the free electricity, isn’t that good? No. The company is proposing to use your roof to receive FIT payments, the overwhelmingly largest proportion of the benefit of a PV system. Your energy savings will be modest.


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