Mayor Parker made the commitment during a speech at the C40, a conference of mayors from around the world who gather to discuss climate change.
Parker has made environmental sustainability a mainstay of her time in office.
The city government has already reduced its greenhouse gas emissions by 26 percent since 2007. She now promises another 10 percent reduction by 2016.
"Most of the decisions that we have made have actually been cost-beneficial to the city's bottom line. It's great when you can do the right thing for the environment, but also provide a better service at a better cost. For example, the City of Houston has 27 electric vehicles. When you consider that there's an upfront cost differential, we're still saving $100,000 a year in fuel costs."
Parker calls the new round of reductions low-hanging fruit.
She says they'll expand the electric and hybrid fleet, continue to retrofit municipal buildings with more energy-efficient materials and increase the amount of wind and solar energy the city purchases.
They'll also change some light bulbs.
"We had a tremendous payoff by replacing incandescent bulbs with LED bulbs in our traffic signals across the City of Houston. And we know that we're saving something like $3.6 million a year in that program."
So Parker's team is in discussions with CenterPoint to put LED bulbs in street lights around the city.
As of 2010, Texas had the highest amount of greenhouse gas emissions in the nation, most of it coming from the energy industry and transportation.