With Earth Day just around the corner, The Charles Hotel is planting some green of its own by decreasing parking rates for compact cars in its garage.

Starting April 22, The Charles Hotel will debut the nanoMAX small car detection system, which will gauge the size of vehicles and automatically encode the information onto the dispensed parking tickets.

To reward drivers who choose environmentally-friendly vehicles, compact cars will receive a discounted rate. Normal and oversized cars will not see an increase in parking fees.

“We’re constantly looking for ways to make contributions to the community and the environment,” said Alex Attia, the hotel’s general manager.

Attia also said there were financial considerations to the decision. Because of how green-conscious Cambridge residents tend to be, Attia said he expected a positive response to the initiative and increased business for the garage, which he said would compensate for the loss of revenue from the parking discount.

Currently, the garage charges $34 for overnight parking and offers a ten percent discount for hybrids. The discounted rate for compact cars has not yet been determined.

“I’m all for it,” said Jeff Meraj, a first year Harvard Kennedy School student who said he frequently parks his Honda Civic at the garage. Though he said the rate reduction would probably not induce people to switch vehicles, he said that the initiative “definitely increases awareness of environmental issues.”

Though Benjamin J. Muchler, a Boston resident who owns a Volvo SUV, will not benefit from the discount, he said he supported the hotel’s decision.

In addition to parking discounts, The Charles is honoring Earth Day by opening a “juice bar” in the garage, where customers can charge their hybrid and electric cars for free.

The hotel will also offer a complimentary bicycle program, allowing its guests to explore Boston without guzzling gas.

The Charles is not the only Boston hotel with an environmental conscience. The Seaport Hotel near Logan International Airport is offering complimentary parking for hybrid cars during the entire month of April.

“We’re strongly motivated by environmental concerns,” said Matthew V. Moore, the hotel’s director of rooms and environmental programs. “The complimentary parking is our way of giving back to those guests who share a similar environmental philosophy.”

Across the river, The Hilton Boston Back Bay Hotel has implemented numerous energy conservation measures in place, such as room occupancy sensors that automatically modify thermostat settings and new energy-efficient heating and cooling equipment and laundry machines, according to General Manager Christian Coffin.

Though it has a parking garage, the hotel has not considered altering parking rates to commemorate Earth Day, he said.

—Staff writer Liyun Jin can be reached at ljin@fas.harvard.edu.