Oncor is offering cash to any household that uses technology to heat household water with the sun, sort of like sun tea.

The power-line business of Energy Future Holdings announced Monday that it’s expanding a solar-electricity incentive program to include solar water heaters.

With the Oncor incentive on top of a federal tax credit, it can take less than 10 years for the water heaters to pay for themselves in terms of utility-bill savings.

Oncor spokeswoman Carol Peters said the company set aside $2 million for the incentives, or between $600 and $1,500 per installation, for the next four years.

The water heaters, which cost $8,000 on average, can cut average electricity use by as much as 250 kilowatt hours a month, according to Jim Cika, manager of solar products for Velux America Inc., which makes solar water heaters. Cika’s systems could trim a North Texas utility bill by around $30 to $35 a month.

“It really compares well with investing money in a CD or even in the stock market,” said Mike Bell, head of EnergyShop, a solar installation company in Carrollton that’s participating in the Oncor program.

“It’s much safer,” he said, chuckling.

Solar water heaters use a roof panel, filled with antifreeze, to collect solar heat. The antifreeze cycles through a tube that coils inside a water tank, transferring the solar heat into the water.

The solar panel can heat up to 80 percent of a household’s hot water; the rest is heated by electricity or natural gas.

Oncor will pay only for systems in homes that use electricity to heat water, and thus relieve electricity demand.

Bell and Cika said business is good for solar energy equipment thanks to a federal tax credit that pays for 30 percent of each installations, as well as local incentives.

It’s a rare bright spot in the recession, and money from the federal stimulus bill could help even more.

“I think right now, with the uncertainty of the stimulus package and how the money is going to be distributed for some of these things, it’s slowing things down a little bit” for solar installation demand, Cika said.

Bell said he expects to hire two to four more people this year to install solar equipment for his company, which employs 10.