Electrical meters are on every home, apartment and business in the valley. They measure the amount of electricity you use, and determine how much you pay.
But meters that required a "meter reader" to check are vanishing -- along with meter readers' jobs. That's because newer smart meters transmit information directly to utility companies.
It's a cost cutting move -- but is it also costing some people their health?
"One day I was sitting in my living room and I started getting these intense chest pains," says Rita Field, who lives in Prescott.
The apartment she shares with her dog is only ten feet away from a wall of APS electrical meters.
"My neighbor said I bet you are affected by those smart meters and I said smart meters what's that?"
Smart meters are wireless devices that use technology similar to a cell phone.
"The new meter is exactly like the old one, the difference is the new meter has communications equipment in there that will communicate to APS hourly usage," says Damon Gross of Arizona Public Service.
We watched as an APS worker installed a smart meter. It took only about two minutes.
Salt River Project has installed 803,000 through May 1, while APS is also over 800,000 installations state wide.
"It's become rather routine and we've been doing this every day."
Gross says the meters also provide information to customers online.
"Now customers have access to their usage information at various intervals throughout the day."
And he says the meters pose no health risk at all -- mostly because unlike cell phones, people don't hold smart meters next to their heads.
"The radio in the meter has about one one thousandth of the radio frequency level of a smart phone," says Gross. "It's a 900 megahertz radio which is the equivalent of a baby monitor."
"These meters are very safe and they provide a lot of benefit to our customers."
Like Rita Field in Prescott, Cindy Dubac says she is electro-magnetically sensitive.
Dubac claims she was perfectly healthy until smart meters started being installed in her Scottsdale neighborhood.
"I didn't have headaches didn't have heart problems, didn't have insomnia," says Dubac.
Dubac has a background in alternative health care, and used to run a health food store. But at first, she didn't know what was happening to her.
"I almost had a massive heart attack and I don't have any heart problems."
She purchased an accoustimeter to measure electromagnetic fields, the same thing electricians use to find electrical lines behind walls in your home.
"This side is actually showing that smart meters are being fired right now," she demonstrates.
When APS arrived to install a smart meter in her home, Cindy pulled out her device.
"Their eyes were as big as plates they couldn't believe what they saw."
She showed us how her device reacts when held near a neighbor's smart meter.
"I told them to remove it immediately."
Smart meters, along with cellular phones, microwave ovens and other electronic devices, produce electro-magnetic, or radio frequency fields.
The invisible waves of magnetic fields generated by every electrical device have been studied for years.
Cell phones, cell phone towers, and power lines have been linked in some studies to possible health problems.
Those people who feel their effects are called electro-magnetically sensitive. But what about smart meters?
"What I can tell you with confidence is that if there is a risk it is extremely low," says Doctor Ken Mossman is an ASU Professor of Health Physics.
He tells us there is no evidence that radio frequency waves from smart meters pose a any health risk. But he doesn't rule it out either.
"I respect people that they have these sensitivities that they react in a way that's different than other people, but there is no medical explanation for why this sensitivity occurs at all," he says. "In fact it is so low you can not measure it with any confidence and it's essentially a risk that is theoretical."
Dr. David Carpenter is public safety expert from the University at Albany. He is often quoted by those opposed to the use of smart meters. We talked to him online via Skype.
"Smart meter issue surfaced only about a year ago," he says. "There is at least the possibility of radiation exposure to radio frequency fields which in my judgment are likely to increase the risk of several diseases."
He worries that radio transmissions from smart meters are just the latest from a long line of devices that have a cumulative impact on our health.
"Those of us who are concerned about smart meters feel that we are as a society are adding to our exposure to radio frequency fields at just an exponential rate."
Carpenter believes there is growing scientific evidence that these radio frequency waves like those broadcast by cell phones and smart meters are dangerous
"These people who complain of the headaches, memory loss and those kinds of symptoms are not just psychotic people, but are really suffering from hypersensitivity to radio frequency fields," says Carpenter. "And in my judgment the evidence that they do constitute a hazard is now growing enormously and I see it as being very convincing."
"I was nervous a lot and I couldn't sleep," says Loni Rosser lives in Mesa.
She first noticed health issues when cell phone towers near her switched to 4G smart phone receivers.
"I had numerous cell phone antennas around my house and had direct radius into my home."
It got even worse for her when a smart meter was installed by SRP.
"I started having tightness in my chest and severe pain in my gut, just intolerable pain."
She asked the utility company to remove it.
"They don't think threes anything wrong with the smart meters but they were fine with taking them off," says Rosser.
Both APS and SRP tell us they will remove smart meters when asked. But if smart meters pose no health risk at all -- then why remove them?
"Our job is to respond to our customers needs and if they express a desire for whatever reason they don't want this on their home then it's our job to see if we can find a plan that accommodates that," says Gross.
Rita field asked APS to remove the smart meters on this wall, but since she was not the property owner, her initial requests were denied. So, she wrote a letter to the mayor of Prescott.
"When the mayor intervened all of a sudden APS did a 180 and said oh we are going to take these all off for you and put in non transmitting meters."
So for now, the smart meters are gone. And Rita Field hopes it stays that way.
"If they are safe and tested I wouldn't be hurting and neither would a lot of other people who are also having the same things if they were safe."
Removing a smart meter may lead to higher costs for homeowners.
APS says they will request rate hikes for those customers still needing a meter reader to come to their home.