Universities are hotbeds of learning, but many are also leading the way when it comes to embracing sustainable, clean energy.
The U.S. Environmental Protection Agency (EPA) ranks higher education institutions on their green credentials, as part of its Green Power Partnership.
CNBC takes a look at the top 10 colleges and universities on the list.
By Anmar Frangoul, special to CNBC.com. Follow him on Twitter @AnmarFrangoul
Annual Green Power Usage (kWh): 85,926,100
According to the EPA, the University of Utah purchases more than 85 million kilowatt hours of wind power every year to reduce its reliance on fossil fuels.
According to the university's sustainability resource center, all new construction projects that cost more than $2.5 million are "required to achieve Silver Certification from the U.S. Green Building Council's Leadership in Energy & Environmental Design (LEED)."
To keep track of energy consumption, all buildings on campus are being fitted with energy metering devices.
Annual Green Power Usage (kWh): 91,372,000
Students at the University of Tennessee pay a "green fee," or a student environmental initiatives fee, as it's officially known.
The contribution – $10 for in-state students per semester, $35 for out-of-state students – goes towards a host of green initiatives.
These include the purchase of renewable energy credits and bike racks on campus that encourage clean transport, as well as helping to divert more than 17,000 tons of waste from landfill sites.
Annual Green Power Usage (kWh): 96,678,000
According to Drexel's website, three quarters of its buildings make use of building automation systems which help to control a host of features, including lighting schedules and temperature control.
Eleven shuttle buses at the university use a biodiesel fuel with 20 percent soy blend, while halls of residence use energy efficient laundry machines and water saving shower-heads that save around 10 percent of water.
Annual Green Power Usage (kWh): 101,339,001
Sixty nine percent of electricity used at Oklahoma State University (OSU) comes from green power, according to the EPA.
Since 2007 the university has saved more than $30 million thanks to the OSU's energy conservation program, while the university makes a point of recycling everything from scrap metal and plastic bottles to lab glass and chemicals and fluorescent bulbs.
Annual Green Power Usage (kWh): 119,013,466
Pittsburgh, PA, based Carnegie Mellon receives all of its electricity from renewable resources, according to the EPA.
Several buildings at the university are Leadership in Energy and Environmental Design (LEED) certified, including the Gates Hillman Complex, which is built on a former industrial site.
The building reflects Carnegie's commitment to sustainability: a "greywater system" on the building's roof gathers rain and melted snow, using it to flush toilets, while more than 15 percent of the building's materials have been made with recycled materials.
Annual Green Power Usage (kWh): 120,839,000
Described by the EPA as "a regional leader and role model for other large public universities," the University of Oklahoma uses smart meters to monitor electricity usage.
In 2008, the university made a commitment to purchase 100 percent of electricity supplied by the Oklahoma Gas & Electric Company from renewable sources by 2013, while a vegetative roof system – or green roof – has been installed on the university's National Weather Center.
Annual Green Power Usage (kWh): 122,014,800
By 2016, Northwestern hopes to have reduced its greenhouse gas emissions by 30 percent compared to its 2005 baseline.
The university states that more than $40 million has been committed to the Northwestern Energy Retrofit Fund, while an annual competition is run to see which campus residences can save the most water and energy. In 2013 the Green Cup, as it's known, helped reduce electricity by 55,979 kWh.
Annual Green Power Usage (kWh): 130,241,123
Third placed Ohio State University has entered into what the EPA describes as a "20-year wind power purchase agreement" which will see it "buy 50 megawatts of wind power generation capacity" from an Ohio wind farm every year.
According to the university, energy conservation projects have helped to save $4.2 million and 3.1 million kilowatt hours of electricity since 2007.
Annual Green Power Usage (kWh): 152,370,500
According to the EPA, Georgetown has set itself the ambitious target of cutting its carbon footprint by 50 percent by 2020, when compared to 2006 levels.
In 2013 the university – which was founded in 1789 – installed 18 kilowatts of solar capacity on university buildings. The university says this will provide the "same carbon reduction benefits as planting 333 new trees or removing 44 cars from the road for a year."
Annual Green Power Usage (kWh): 200,000,000
UPenn is described by the EPA as the United States' top "purchaser of wind power among all colleges and universities."
Green and sustainable features include an "operations command center" which helps to save over $5 million annually through what the Ivy League university describes as "state-of the-art central monitoring and control of utilities."
Green roofs are being installed on the top of buildings to capture rainwater, while a pedestrian street runs right through campus.