I had a question awhile back from a reader who had a smart meter installed and checks online for usage.

The reader reported that usage was normal for one or two days, then surged for the next day or two. There is no pattern to the surges. She said it was almost like a timer was turning on.

I published some of your responses almost a month ago, but as my column gets published in newspapers throughout the country, more have come in since. So here goes:

Lee Edelberg in Leverett, Mass., says I was correct to ask about their heating and hot water, and adds a couple of thoughts.

He says a well-insulated electric water heater may not run much every day if its hot-water usage is low. It may stay hot enough for a day or so, then kick on to reheat the tank. Another possibility would be electric dryer usage. Maybe the reader does a lot of laundry and didn’t consider the impact.

Joe Riggins, an electrical engineer who lives outside Ithaca, N.Y., asks if the reader is sure she is looking at kilowatt hours?

“The rate can be more than twice that of a previous day resulting in a variation in cost,” he says.

John Walker spent many years working in customer service in the billing-inquiry area for a large utility company.

“This involved field trips to determine high usage to rule out over-readings, previous estimates,” he says, adding that “newer electronic meters rule out most of the old problems.”

Walker has found “many strange reasons for sporadic use increases, but this sounds like it could be due to underground wiring to an outbuilding with a two-way switch, one leg of which is exposed to dissipation conditions.” (Turning on a light in the house and off in the garage could create this situation. If the action is reversed, it will clear.)

Byron Goldstein suggests that most refrigerators and freezers have automatic defrost cycles — “the defrost coils are electric, and then the unit has to rebound from the heat, requiring more cooling.

“It’s always a good idea to check the refrigerator coils, in back or underneath,” Goldstein says. “Even with supposedly self-cleaning coils, they need to be cleaned once or twice a year of dust and dirt for efficiency.”