Virginia Electric and Power Co. received a $64.1 million rate increase yesterday that initially is expected to add about one percent to its customers' monthly bills.

The revised rates, approved by the State Corporation Commission in Richmond, will go into effect in two steps, starting with an $18.1 million increase on April 1. The second rate change, however, will result in a reduction in electric costs, according to Vepco officials.

The reason for the expected cost cutback is that the second rate revision will become effective when Vepco's second North Anna nuclear generating unit begins full-scale operation. The costs of putting the North Anna 2 plant into service "will be more than offset by the fuel saving this nuclear unit will provide," a Vepco official said.

The April 1 rate rise will add 79 cents to the monthly bill of a customer using 1,000 kilowatt hours of electricity a month, according to Vepco and SCC officials. This represents a 1.3 percent increase for such a customer, from the current $62.48 monthly charge to $63.27.

Consumption of 1,000 kilowatt hours a month is described by regulatory officials as close to the average for most of Vepco's 1.1 million Virginia customers. Owners of "all-electric" homes use considerably more electricity, however.

No date has been set for the second rate revision because the Nuclear Regulatory Commission has not indicated when it will permit North Anna 2 to go into service. If North Anna 2 starts full-scale operation later this year, Vepco rate manger H. M. Wilson said yesterday, the net monthly savings for a customer using 1,000 kilowatt hours a month would be $2.50.

The reduction in costs would occur because nuclear fuel is normally a cheaper source of electric power than oil or coal. Vepco officials said the utility's "fuel factor" -- an amount reflecting changing fuel costs -- would decrease when North Anna 2 starts full service, more than offsetting other expenses for the plant.