Arlington County is considering an energy tax on residents to help pay for its high-profile initiative to reduce greenhouse gas emissions, officials said yesterday in proposing a $873.6 million spending plan for the coming year.

Arlington residents could pay as much as $26 more on electricity and natural gas bills next year if the County Board decides to include $1.5 million for the environmental initiative in its spending package, which the board will consider in April.

The money would go toward solar-powered projects, energy audits for homes and an "aggressive outreach and marketing effort" on energy-saving measures for residents and businesses, officials said.

The county is in the middle of a major push to reduce its greenhouse gas emissions by 10 percent by 2012, and the "modest" utility tax may encourage residents to curb consumption, County Manager Ron Carlee said. Officials are also planning a tax break for the 1,000 owners of hybrid vehicles in the county.

Yesterday, Carlee introduced a proposed budget with a 5 percent spending increase, including $1.3 million to cover federal funds lost last year in a dispute with the state over social services reimbursements.

Budget forecasters in the county initially predicted a $20 million budget shortfall in the coming fiscal year because of the cooling housing market. But although home values in Arlington fell 0.8 percent last year, the county was able to bridge that gap because of a larger-than-expected rise in commercial assessments, including a 25 percent increase in the apartment market, mostly attributable to rising rents. The county gets 58 percent of its revenue from residential real estate taxes.

"This allows us the ability to take care of the most vulnerable residents in the county while providing us the opportunity to address emerging issues -- such as the environment," Carlee said of the property tax outlook.

The $1.3 million in social services funding includes $261,000 for school-based mental health services, $130,000 to finish repairing an assisted living residence for mentally disabled seniors and $358,000 for an adult day-care program at the Walter Reed Community Center.

The county proposed that the school system receive $329.7 million, an increase of 5.9 percent from this fiscal year. The spending plan includes taking over the operation of Head Start classes, expanding a pilot program for foreign languages in the elementary schools, increasing school security and giving a 2 percent raise to staff.

County Board members will also get a raise, which they approved this year. The annual salary will be $49,000 for board members and $53,900 for the chairman.

Carlee said that the spending plan proposed yesterday includes no increase in the real estate tax rate, but he left open the possibility of increased taxes next year for a proposed $3 million storm water management project.

Another option would be to bill residents directly -- as the county now does for water and sewer service.

That storm water management program -- which is subject to board approval -- would upgrade rusting culverts, impose erosion controls and make other federally required improvements intended to protect the Chesapeake Bay.

But officials said it was "unlikely" that the county would raise the real estate tax rate.

"This is a proposal, and there are several ways to pay for it," said Mark Schwartz, the county's finance director. "The board will have to decide how they want to fund it."