A defective meter or a problematic hot water heater ran up a Mastic Beach couple's electric bill by thousands of dollars, but which is actually to blame depends on who you ask.

Deborah Watson says she doesn't turn her air conditioner on often. She says she can't risk another increase in her bill.

"When we first moved in, our bill was only going to be $335," she says of the house she moved into with her family three years ago. "Then it went up to $496."

Then it climbed as high as $639 for months on end, she says.

"There's no way this house used $639 worth of electric," she argues.

She assumed then that the problem must be a faulty meter. She says a PSEG Long Island employee who came to her home even told her that was the case. The worker replaced it with a new one, but PSEG says it replaced the meter for testing and found nothing wrong.

"We actually found that her meter was working fine, well within the threshold of a regular meter," says PSEG spokesman Jeffrey Weir. 

The utility company investigated. Watson doesn't have central air conditioning, an in-ground pool or a hot tub. What was the problem? It turned out to be her hot water heater, PSEG says.

"We found that her heating system was not hooked up correctly -- in fact, not only was it drawing too much energy, but it was also incredibly unsafe," Weir says.

Deborah says her bill has gone down to between $200 and $300 per month since the meter was changed. But she admits she also had the hot water heater shut off during that same period. 

Both sides claim vindication.