In a private electricity industry that’s bilked at least $77 million from Maine residential customers, new entrants are trying to sell on something lacking: trust. A series of websites and services are cropping up to help customers navigate the electricity market, providing price listings from different companies in one place. But the top consumer watchdog in Connecticut — a more mature market for home electricity sales — is skeptical the sites have shoppers’ best interests in mind. The sites have problems, said Connecticut Consumer Counsel Elin Katz, ranging from misleading to possibly fraudulent claims.