What’s on a company’s rooftop these days? Increasingly, you’ll find a rooftop solar garden and wind power installations.

Two major retailers announced plans this month to add renewable energy systems to their rooftops to generate supplemental power and reduce their contribution to greenhouse gas (GHG) emissions.

JC Penney just announced its plans to add solar and/or wind power systems at 200 or more of its retail stores by 2011.

The company earlier this year got its solar program rolling in a deal with SunPower Corp to install solar systems at five New Jersey stores and four in California. Each unit will generate between 259 and 602 kilowatts of clean power. The New Jersey solar arrays will reduce JC Penney’s carbon dioxide (CO2) emissions by 105 million pounds over the 30-year life time of the solar equipment. The company’s California solar systems will cut another 86 million pounds of CO2.

Bottom line: The solar arrays will cut JC Penney’s electricity bills by 25%.

Click here for the company’s release.

JC Penney is also adding wind technology to a rooftop at its distribution center in Reno, NV. The AeroCam wind turbine will be supplied by Texas-based Broadstar Wind Systems. For graphics on the AeroCam turbine, click here.

Wal-Mart announced a similar deal with SunEdison to install rooftop solar systems. Wal-Mart’s first installations will be on five Puerto Rico stores. The retailer will add solar arrays to another 23 stores over the next five years. Like JC Penney, Wal-Mart expects to economically benefit from the investment by reducing its electricity bills from 25% to 35% at each store.

Wal-Mart’s release is here.

Tags: JC Penny, renewable energy, solar power, Solar Power Systems, SunEdison, Wal-Mart, wind power