Energy efficiency means using less energy to provide the same service. For example, using an Energy Star certified refrigerator will use less energy to provide the same service that a traditional refrigerator provides, or using a compact fluorescent light-bulb to produce the same light as an incandescent while using less than 1/4 the electricity. Efficiency improvements are often the most cost-effective methods to reduce energy use and carbon emissions; in fact, most energy-efficiency improvements pay for themselves in energy savings relatively quickly.
Renewable energy is generated from resources that are indefinitely replenished naturally, including: sunlight, wind, water, hydrogen, biomass, and geothermal heat. While using less energy is very important, cleaner sources of energy will also be vital to creating a more sustainable city.
Each year the City of Pittsburgh purchases 25 percent of its energy from renewable sources, which is enough to power 3,500 homes per year.