If you were thinking about installing solar on your home this year, you might want to hurry up. Residential solar incentives in at least two major metropolitan U.S. areas, Detroit and Los Angeles, have already dried up, and others are likely to follow.

The incentives offered by local utilities are limited, and demand in the region has exceeded the funds that have been allocated for the programs—even before the mid-point of 2011 is reached. The Los Angeles Department of Water and Power (LADWP) suspended taking applications for its Solar Incentive program in April and today (May 6) DTE Energy (NTSE: DTE) said the residential part of its SolarCurrents program was fully subscribed.

SolarCurrents was a pilot program, according to DTE Energy spokesperson Scott Simmons.

“It was limited to 5 megawatts; it’s fully subscribed,” he said.

Since it was a pilot program, the company didn’t have a projected timeline.

“One of the things we wanted to learn was what kind of demand was out there [for solar], subsidized or not,” he said. “We know that there are a lot of people that want to get off the grid, and as far as total installations, in our service areas, there were about 500 [made under the program]. It’s pretty much what we expected.”

The residential portion of the SolarCurrents program was funded by DTE at $25 million, according to Simmons.

The company is now taking a look at its entire renewable energy program, Simmons said.

“Whether that includes looking at future incentives, it has yet to be determined,” he said. The company will file an amended renewable energy plan with the state in June.

The LADWP Solar Incentives program, which has been in place since 2007, was inundated with requests.

“As of April 1, 2011, the LADWP Solar Incentive Program had confirmed requests for $112 million in solar rebates, but only $30 million is budgeted annually for the program,” the department said in press release.

The municipal utility is now evaluating the program, according to a spokesperson. The utility will evaluate the applications it received prior to April 8—all 2,000—that it is currently processing.

“We fully support and want more renewable energy, and we want to foster solar technology, but not at undue expense to our customers who pay for this important program,” said Ronald O. Nichols, LADWP General Manager. “We need to be smart about how we provide incentives and that starts with ensuring we are doing so in a fiscally responsible manner.”

Image courtesy of NREL.