The eco-home evangelist who cut her electric bill to just £5 a year

SUE Roaf is an enviable woman. Not only is she professor of architectural engineering at Scotland's prestigious Heriot Watt University but she also has an annual home electricity bill of just £5.

The astonishingly low bill comes from Roaf's former home near Oxford where she lived before moving to Scotland to take up her new academic position earlier this year.

Built in 1995 as a pioneering example of an 'eco-home', the six-bedroom house incorporates many of the simple features that cut down on the use of electricity and gas, keeping it heated and powered for a fraction of the average bills generated by most other houses.

Roaf, who is helping to develop designs for an eco-house that is suitable for the Scottish climate, is now planning to build a new home near Edinburgh to put her ideas into practice and create Scotland's first eco-community.

She wants to provide an example of how new homes could be built both to cut down on the carbon emissions produced by power generation and save owners hundreds of pounds a year in fuel costs.

One of the main reasons for her staggeringly low electricity bill (the average in Scotland is £366 per household per year) is a range of photovoltaic roof panels which convert sunlight into electricity.

She generates so much from solar power that she can sell the surplus to the National Grid.

Solar panels now cost around £5,000, although there are Government grants to reduce the outlay by up to 50%.

"I installed the first solar electric roof in the UK and it is the best thing I did in terms of a sensible investment," said Roaf. "Every year it generates more electricity - because the summer appears to be getting longer - which I can then sell. I am pretty certain that I will soon be making a profit."

The design of her new house will be similar to those being built by Glasgow architect John Gilbert, who specialises in low-cost, low-carbon homes.

Roaf said: "To get really low energy use and reduce your carbon emissions you have to halve demand. You can do this through good architecture, good insulation and making sure there are no draughts.

"You then replace your household appliances with ones that are double the efficiency. That leaves you with a quarter of your original energy use. Of the 25% left, half you can generate yourself through renewable energy systems so you are left with one eighth."

One barrier is the cost of installing energy-saving measures. An Alliance and Leicester Building Society survey last week said it costs around £9,000 to make a three-bedroom house cheaper to run.

Measures included loft insulation, which costs about £370 but can reduce energy bills by around £110 per year, wall insulation, replacing old gas boilers, double glazing and installing renewable power generators such as wind turbines or solar panels.

All require an initial outlay but experts say that they will eventually pay for themselves. "There are people who spend up to £100,000 on a kitchen," said Roaf.

"Wouldn't it be better to spend the money on good draught-proof windows and solar heating? It could be the best money you have ever spent. Scotland has a longer heating season so you need as much cheap heating as you can get. An established eco-community could be an example for the rest of the country."