Dr Leggett lives in a terraced house in Richmond, Surrey. His gleaming metal-grey tiles were installed three months ago and have generated 337kWh, though he needs only 232kWh. The surplus is sold to Seeboard, the local electricity company.
Dr Leggett, who dubs himself the "chief executive of the Solar Century" (a "green" energy group) is delighted to have confounded sceptics who claim that solar energy is a contradiction in this cloud-covered land. On sunny days his roof generates enough excess electricity, which he feeds back in to the grid, to cover what he draws out at night and when it's overcast.
In principle, Britain's energy policymakers support solar power. A Government-sponsored solar taskforce concluded recently that photovoltaics could be "the single most important long-term means of reducing gas omissions" and one of the most cost-effective means of getting energy.
And yet, while the US plans a million solar-tiled homes by 2010, Germany 100,000 by 2005 and Japan 70,000 by 2000, in the UK, says Dr Leggett, the Department of Trade and Industry has backed a programme for "only 100 and with no firm timescale".
Dr Leggett, a former director of Greenpeace, blames the electricity industry: "No gas, no coal and no nuclear power would be required if every roof was covered with solar tiles. But the power companies have a policy of obstruction. The utilities are lobbying the Government and regulators hard, to stop the authorities allowing customers to get their due."
However, Seeboard, which claims it pays him a fair price for his electricity, says it has no fear of solar-power generation.
To install a 2kW system similar to Dr Leggett's would cost about pounds 20,000. His house, he says, needed a new roof (costing up to pounds 7,000) anyway and, while installing the solar tiles, he got a loft conversion, thereby increasing the value of his property by about pounds 25,000.
The Solar Century has negotiated a "solar mortgage" with a bank to persuade 100 pioneers to have the system installed this year in show homes across the country.
Dr Leggett says that on a typical day his roof creates enough power for 350 cups of tea, 70 Coronation Street episodes and 800 slices of toast.
The Solar Century can be contacted at 0870 735 8100