NASHVILLE, Tenn. -- Nashville residents' energy bill could soon skyrocket. Nashville Electric Service said it's because its technology is advancing, but some local families say the changes only put them behind on payments.

Video: New NES Meters May Cause Energy Bills To Rise

Older meters are getting replaced one by one with newer digital meters. NES said the digital ones are more efficient, but some customers who already have the new meter say it isn't as efficient for their bottom line.

“I said, 'He's messing with my meter, and I got it where I want it to be,'” said Brenda Anderson.

Anderson is preparing for retirement. In an effort to cut costs, she and her husband cut back on electricity.

“I pushed it down to 60 and just turned it off for the winter and said, 'We're not going to use this because this is what's making our bill go higher, and I’m trying to keep it low,'” said Anderson.

In September, the Andersons' bill was about $45. The next month it was only $26.

“I was so happy when I got it so low, $46.07, I was, like, 'Wow, this is a dream come true for me,'” said Anderson.

However, the dream didn't last long. In December, NES decided the Andersons' meter was not reading correctly, so it was replaced with a new, digital meter.

“When she was upgraded to a digital meter, now she's truly getting an accurate measure of usage,” said Betty Turner with NES.

Anderson is also getting a substantially higher bill. Her tab jumped to about $200 a month. She said it seems as though NES targeted them.

"'Wow, they should be paying more than $45 a month. Let's go change out their meter, see if we can get those numbers flying again,'" said Anderson about NES.

To some degree, NES said, that's true. Several low readings like the Andersons had means NES technicians will take a closer look. In their case, that meant replacing their meter with a digital one.

“If you have the benefit of a really old meter that was not registering properly, and now you get a brand-new meter that does register properly, you may see a little bit higher bill,” said Turner.

NES officials said they plan to change everyone's meter in the Nashville area sometime in the next five to 15 years. They said the older and less-"accurate" meters get replaced first.