Dominion Virginia Power says low temperatures over the past week led its customers to set a record for electricity usage. The Richmond-based energy provider said it supplied a peak of 21,651 megawatts of electricity at 8 a.m. last Friday. That’s over 1,500 megawatts more than the previous record high set in July 2011. The previous winter peak of 19,870 megawatts was set on Jan. 8. Dominion says one megawatt supplies enough electricity at peak for about 250 homes.