Small-scale producers of solar energy can readily link themselves to the grid - but this would prove impractical and costly as most would only generate enough electricity to power themselves, says an executive with CLP Power, one of the city's two main power suppliers. To spur more renewable-energy development and investment, green groups have been urging the government to develop what are known as feed-in tariff policies requiring utilities to buy electricity generated by renewable energy producers at fixed rates. But almost none of CLP Power's 200 customers with small-scale renewable electricity generation capability produce enough to supply to the grid, even though they are all connected to it. "It would be impractical to connect to the grid," said CLP director of marketing and customer services Chow Lap-man. "Most people in Hong Kong won't produce nearly enough energy to sell to the grid, even if there are feed-in tariffs." Chow said that in a city as dense and small as Hong Kong, only large, sprawling institutions such as hospitals or universities, or people who live in standalone houses would have the space to install solar power systems. Chow said most of the public did not have a firm enough grasp of the feasibility of renewable energy production in Hong Kong. Space, cost and return on investment were also factors that had to be considered, he said. An average photovoltaic solar panel system capable of producing 1,500 kilowatt hours of electricity costs about HK$50,000 and requires a return on investment ranging from 35 to 50 years. He said a more practical investment would be a combination of a heat pump and solar water heater, which would cost less than HK$30,000 and save about HK$6,000 a year in power costs for a family of six. The return on investment would be just five years. The city's first such system was installed in February. "We understand there is increased demand for renewable energy. But it is important to look at how to utilise solar power more efficiently," Chow said. Greenpeace campaigner Yeung Man-yau disagreed that feed-in tariffs would be useless, as connecting to the grid without such incentives would mean all extra power generated by a producer would go to the company without payment. He said this would constrain the development of the small-scale market.