OVER THE LAST forty years the world of energy has abounded with predictions, from dire forecasts of the imminent exhaustion of world oil supplies, to the rather optimistic "Nuclear power will be too cheap to meter." But only the truly visionary could have forseen Terminator actor Arnold Schwarzenegger standing before the people of California in 2005, as their governor, launching the world's largest solar roof programme!

Solar heat and power technologies have been making impressive progress in the US over the last decade, mainly through government support programmes like Schwarzenegger's Million Solar Roofs Initiative. A precursor to the Californian programme came in 1997 when President Clinton launched a national Solar Roof Initiative. Without any formal budget it still achieved 229,000 installations by the end of 2003. Earlier still, in 1994, Japan launched a 70,000-roof programme and reached 144,000 residential systems in 2002. Germany upgraded its 1,000-roof programme to 100,000 roofs in late 1998. The programme was such a success that it met its targets early in 2003.

Meanwhile, in the UK the outlook doesn't seem quite so bright. After managing just 600 installations in the first two years the Department of Trade and Industry is to end the Major Photovoltaics Demonstration Programme in March 2006. The programme was due to run until 2012, by which time 70,000 small-scale systems were due to be installed. According to Friends of the Earth UK, on twelve separate occasions since 1999 the German solar roof programme has delivered the equivalent of the UK's initial three-year target in just one month.

The UK programme, along with its solar thermal equivalent, Clear Skies, will be replaced with a non-technology-specific programme and it is as yet unclear how solar will fare against the other technologies that are closer to being commercially competitive.

'Sustained nurture' has been the nascent renewable industry's wish for government policy for some time now, rather than stop-start grant programmes which make investment in industrial capacity so unattractive. In Germany sustained nurture has been enshrined in the Renewable Energy Feed Law, whereby support for photovoltaic systems is fixed per solar kWh produced into the foreseeable future and backed by low-interest loans. The price is set to reduce each year by five per cent, to mirror the reduction in capital costs brought on by the scaling-up of production that the programme facilitates.

In 1999 Greenpeace commissioned business advisers KPMG to examine the economics of photovoltaics (PV). The report Solar Energy: From Perennial Promise to Competitive Alternative concluded that solar PV could be competitive with conventional fossil-fuel power generation if production were scaled up to 500MW peak per year (around 250,000 household-sized systems per year). They estimated that to build a factory of this kind would cost US$660 million. This sounds like a lot of money, but the authors pointed out that the investment equates to just one half of one per cent of current expenditure on oil and gas exploration annually.

Six years later costs have fallen significantly but we are still a long way from the "competitive alternative" scenario that KPMG envisaged. Without grant support, payback periods for solar at current prices are around 100 years for PV in the UK's climate. Clearly more nurturing is required to change the fact that sadly, most people with the money to spare choose a new kitchen rather than a solar roof.

THE SITUATION WITH solar thermal is somewhat different. This is already a mature technology and the potential to reduce cost through scaling up production is not as great. There are estimated to be around 45,000 systems already installed in the UK. Its financial viability is still not exactly a heart-stopping money-earner though, either: the simple payback is around forty years. But with gas prices rising substantially after years of decline, and a range of local support programmes designed to make the technology accessible to the public, prospects for solar water heating are now looking a little brighter.

The possibility of a Renewable Heat Obligation, modelled on its electrical cousin, looks like a real possibility. This would put a requirement on suppliers of heating fuel to source a proportion of their heat from renewable sources - with solar thermal being one of the three permitted technologies. An EU Renewable Heat and Cooling Directive is also being proposed.

Solar enthusiasts in the UK can take comfort from the fact that the uptake of solar in Europe bears almost no relation to climate. The largest markets for solar water heating in Europe are Germany, then Austria and Greece, which together enjoy more than eighty per cent of Europe's installed capacity. Greece clearly has a climatic advantage, but why has Austria achieved almost two million square metres of solar collectors by 2004 - more than twice as much as sunnier Spain, Portugal and Italy combined? Denmark has managed 45m2 per 1,000 inhabitants while the UK has managed just 5m2. Clearly there are other factors at work. Research has shown that public awareness of environmental issues, government intervention through regulation and financial support, and the quality of the products and services offered by the industry are as important as climate in the uptake of solar.

HOWEVER, THE UK hasn't been completely backward in the area of solar power. Few people realise that there is a renewable revolution beginning in our town halls. Frustrated by central government inaction, local authorities have taken it upon themselves to introduce tough new planning requirements for new developments. The London Borough of Merton was the first, and it managed to overturn developers' challenges and steer past a nervous government. Merton's planning system now requires any new large-scale commercial development to source ten per cent of its energy needs from on-site renewable energy. Five London Boroughs and the Greater London Authority have since followed suit, introducing their own ten per cent requirements, with some extending this to residential as well as commercial developments. With solar technologies as the obvious choice to integrate into a new building, and huge swathes of new housing planned for London, this could be the kick-start that the UK solar industry needs.

The prospect of a technology costing in the region of £500 a square metre replacing the humble concrete tile as the roofing material of choice in ten years may seem remote today. But as the price continues to tumble, and with the evidence that the point of irreversible accelerated climate change is getting closer, how long will it be before we view using roofing materials that do nothing except keep the rain out as a shameful waste of space?

Chris Dunham is Director of SEA/RENUE, a not-for-profit organisation promoting sustainable energy use in London.