We were thinking about putting solar-panels on the south-facing roof of our home-extension some years ago, but determined it would take about 20 years to pay-off the cost in terms of the electricity-bill savings that would be incurred. The upshot was we didn't bother. There are conflicting views, however, with the "Rics" (Royal Institution of Chartered Surveyors) saying that "solar panels are one of the least cost effective (home) upgrades" while the solar industry, including the CEO of Solar Century, Jeremy Leggett, claims that the above conclusion is based on faulty-calculations.
According to the Rics, it costs around £4,000 - £5,000 to fit the average house with solar panels (that's about what we reckoned) but the energy savings are a meagre £24 a year (and so that would amount to 160 - 200 years to pay it off!). In their recent report, Rics also maintain that to swap a wall-mounted boiler with a more energy-efficient one costs around £1,700 to equal an annual saving of £95, a lead-in time of 18 years. They claim that the most cost-effective means to save energy is cavity wall installation, at a cost of £440 - £2,400 depending on the size of the home, to yield a saving of up to £145 a year which could be recovered in three years. We did go for this option and thereby insulated the said extension, at a cost of around £500. I'm not sure yet what it saves us in terms of heating, but this is a well-insulated house and our bills are in any case quite modest.
The solar industry has vigorously objected to the Rics's report, for example Andrew Lee, who is head of solar at Sharp Electronics, said: "Rics' claim on solar panels is massively misleading and potentially damaging for both the UK solar industry and the UK's renewable energy targets, being based on outdated and inaccurate information. Instead of 50 years plus for payback, most average installations will payback within approximately 12 - 15 years." Mmmm, that's about what we thought, and didn't go for it either!
Rics also slams the cost-effectiveness of personal wind-turbines: "A large free-standing wind generator (meaning an electricity generator powered by wind-force) can cost anything from £12,000 to £24,000 to install. But they are only really economic or practical for people in rural areas, particularly those not connected to the electricity grid. Even then, and taking account of electricity fed back into the grid, it would take at least 15 years for them to pay for themselves.
However, this is all costed at current circumstances, and in 15 years or more, there may not be the gas or other provision for electricity, and solar could prove a worthy investment. I can imagine that the price of solar and the dubious sturdiness of conventional power supplies will be good reasons to promote nuclear power, on the national rather than the local scale. It is my understanding however, that solar water-heating systems rather than photovoltaic cells are a good energy investment overall, albeit they don't product electricity, but they may save it in heating water per se. For example, we use an electric immersion heater.
Leggett and Greenpeace are both quoted as saying that solar should become cost-effective with conventional energy by 2020 across most of Europe, and Ernesto Macias, president of the European Photovoltaic Industry association claimed that: "solar voltaic electricity has the potential to supply energy to more than four billion people by 2030 if adequate policy measures are put in place today."
I suspect that the scale of manufacture and installation across the world would be colossal and I have calculated before that only through thin-film cells can the level of resource to fabricate so much solar PV be even addressed. How long it will take to install is a fair question, and I doubt the present level of electricity production can be maintained. All considerations seem to anticipate the reality of a lower-energy society.
"Solar panels are a 'waste of money', says Rics." By Andrew Ellison. http://www.timesonline.co.uk/tol/money/consumer_affairs/article4681919.ece