British customers are quite interested in buying their electricity from renewable sources, but they are reluctant to pay more than 10 percent over regular prices for it, according to a new Harris poll on the country’s electricity market. Britain this week completed deregulation of its market, and the poll found that the marketing pull of green energy could be a way for competing companies to attract and keep customers. A separate survey conducted by Gallup in February found that 65 percent of customers were either likely or very likely to switch to a company offering renewable energy, with more than half that number saying they would pay between 2 and 4 percent above normal rates for green power.