Your National Grid electric bill is going to go up this month – probably between $25 and $30.

Blame it on the volatility of the weather.

Wholesale electricity costs are expected to be 6.95 cents per kilowatt hour in May, although another 1.69 cents will be added to the supply charge to true-up the actual cost of electricity last month, when there was a 2.6 cents credit that lowered the supply cost considerably.

You want the bottom line?

To estimate what the increase will be this month for a typical Capital Region household, we took a real bill from a National Grid customer in Delmar who has a household of four people.

They used 522 kilowatt hours of electricity between March 13 and April 15.

Last month, their electric bill was $65.86, an amount that is due in about nine days.

If they use the same 522 kilowatt hours before their next billing cycle ends about two weeks from now, their electric bill will be $91.25, an increase of $25.29.

If you use more electricity – maybe you have two big-screen TVs and a treadmill – your electric bill may rise more, perhaps $30.