When Martin and Celeste Wilkinson had an electricity-producing photo-voltaic solar array installed on their roof in March, they became the first homeowners in Bettendorf to do so.

They expected the array would supply 50 percent of their electricity, but so far it's been doing better than that, producing 100 percent and producing an actual credit with MidAmerican Energy Co., Celeste Wilkinson said.

In winter, when the sun doesn't shine as much and electricity production goes down, the couple will draw on their credit.

Although a solar array for the typical home ranges from $15,000 to $25,000, according to the Anamosa, Iowa, company that installed the Wilkinsons',  it can be expected to pay for itself within seven to nine years.

That means that by year nine, homeowners such as the Wilkinsons will have saved enough money on their electricity bills to pay for their system, Jason Gideon of the Energy Consultants Group, said. Anything saved after that is free money.

"Plus you're doing your part for the environment," Gideon said.

A federal income tax credit up to 30 percent of the cost and various state financial incentives can reduce the upfront expense by 45 percent, Gideon said.

Still, people are reluctant, and the residential solar market isn't growing very fast.

A majority don't want to pay the upfront costs, Gideon said. "I tell them that if they do nothing, they're going to pay $120,000 in electrical bills in 30 years. But if they can't get it back in the first year, they're not interested."

Bill Haman, renewable energy program manager for the Iowa Energy Center in Ames, agreed that solar energy had been slow to be adapted in Iowa because of its high initial cost and "the relatively low electric rates that Iowans pay, particularly MidAmerican Energy customers."

Those two factors combine to make the economics challenging to justify, he said.

And to take advantage of the tax credits, people need to owe federal and state taxes, Haman pointed out.

But "dramatic drops in solar energy equipment prices combined with lucrative tax incentives have spurred the dramatic rise of solar energy investment," he said, particularly among livestock producers.

The Wilkinsons installed the system because they've long been interested in, and support, renewable energy, Celeste Wilkinson said.

Their home also has a geothermal heating system and tankless water heater (heating water on demand), and they drive a hybrid car.

They hired Energy Consultants Group after doing online research. "We wanted someone who had done it awhile," Wilkinson said. "Gideon had gone to Germany where it (solar) is done a lot. He seemed knowledgeable."

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The Wilkinsons have an array of 60 modules on the back side of their roof that faces south, for optimum exposure. The number of modules one chooses to buy depends on how much of your electricity needs you want to generate and how much you are willing to pay.

"Size will dictate the cost," Gideon said.

The electrical needs of a house have almost nothing to do with square footage, and everything to do with the habits of the occupants, Gideon explained.

"Occupants are what uses the energy, not the home," he said.

Electricity is required to run the fan/blower of a furnace/air-conditioner, and that is fairly constant among homes. After that, electrical use comes down to lights and appliances, both large ones such as refrigerators and small ones such as hair dryers. Their efficiency, number and amount of use is determined by the occupants.

Advantages of solar modules are that they require little to no maintenance,  work every day, have no moving parts and can be fitted to any site, Gideon said. In addition to being mounted on a roof, they can be installed on poles on the ground and some are "directional" in that they will move to follow the sun.

One maintenance task would be to remove snow or heavy dust that might cover the arrays and interfere with production, he said.