By switching to energy-saving street lights and using remanufactured printer toner cartridges, the City of Palo Alto could save as much as $500,000 — and significantly reduce its greenhouse-gas emissions, the City Council learned Monday night.

But determining when and how to enact those two proposals, as well as dozens of others presented as part of a cost-benefit analysis of climate-protection measures, requires additional study, the council decided unanimously — minus absent council members Greg Schmid and Yiaway Yeh — Monday night.

"I want to see us move as aggressively as possible, but I also want to see us move as effectively as possible," Councilman Pat Burt said.

The city's four-member Sustainability Team had recommended a council decision on the issue by December, but at the request of Mayor Larry Klein, the council will reexamine the emission-reducing actions sooner, in September.

The cost-benefit analysis stems from the council's adoption last December of the Climate Protection Plan, which calls for the community to slash emissions by 15 percent by 2020.

The analysis identified 12 actions — ranging from allowing city employees to work from home two days a month to the installation of extra bike racks — would each cost less than $50 per ton of emissions reduced, costing the city $1.8 million.

Other actions included replacing two city vehicles with hybrids, buying back parking spaces for city-employee commuters, increasing participation in PaloAltoGreen (the city's optional renewable-energy program) and other methods of increasing the use of renewable energy.

Combined with the two money-saving measures, the city could reduce about 64,000 tons of emissions by spending $1.3 million, Sustainability Team leader Nancy Nagel said.

The city's budget has only a slim surplus this year, complicating the city's ability to enact costly changes, City Manager Frank Benest warned the council.

Several council members, including Yoriko Kishimoto and Burt, challenged several of the analysis's assumptions and conclusions.

The analysis examined the Stanford Medical Center and Shopping Center expansions as an example of a land-use-related emissions inquiry.

Without any mitigation measures, the two major projects would add about 73,000 metric tons of greenhouse-gas emissions, about 10 percent of the community's current emissions, the staff report stated.

Interim Deputy City Manager Steve Emslie said transportation and vehicle trips were a major component of that estimate.

City staff members divided the cost-benefit analysis between the Utilities Department, environmental consultants URS Corporation and Stanford Environmental Consultants, a team of Stanford students.

First, staff whittled down the 120 actions included in the Climate Protection Plan to 25 that could be quantified, Nagel said.

Some of the measures studied have already won the council's support, including mandatory recycling and green-building policies.

The 144-page Climate Protection Plan, available at www.cityofpaloalto.org , was created using information generated by the Green Ribbon Task Force on Climate Protection.