San Diego Gas and Electric will switch customers to a new billing plan called Time of Use beginning Friday.
While the new plan is optional, all customers will be automatically enrolled unless they decide to opt out, according to the utility.
The most expensive hours will be from 4 p.m. to 9 p.m. when many San Diego County residents return home from work or school.
SDG&E said in off-peak periods during the summer, a customer could spend around 22 cents per kilowatt-hour. That cost will double between 4 p.m. to 9 p.m.
“We're encouraging people to keep up with their daily routine. it's just thinking about those large appliances like your dishwasher, your laundry and maybe shifting the time of day you use some of those things and that's going to translate into some savings in your bill," Wes Jones, SDG&E Communications Manager told NBC 7.
The amount of renewable energy available declines as the sun goes down, SDG&E said. At the same time, demand increases.
The utility says they are hoping the new plan will encourage users to conserve energy.
Since solar energy systems generate most energy in off-peak hours, those customers could lose money because the energy their panels create will be compensated at a lower rate.
"However, if solar customers can perhaps pair up their solar system with battery storage, that can be a great way for consumers to save energy, keep it charged and then use it when they come home in the evening," said UCAN Executive Ed Lopez.
Enrollment into the new plan will begin in phases with the first customers switching over on Friday.
For the first year, SDG&E customers will receive a shadow bill which will show what they would have paid under their previous plans.
SDG&E tells NBC 7 that those customers who end up paying more under the Time of Use plan will get a credit for the difference in the first year.