You’ve probably seen many of the ratings systems and codes tossed around, but do you know what they mean? Here’s a quick guide to the most common energy efficiency ratings and how to interpret the scores.

HERS. The Home Energy Rating System (HERS) measures the energy efficiency of a home and assigns a performance score. This rating is based on the efficiency of a standard new home. A home that was built according to the 2004 International Energy Conservation Code receives a HERS score of 100.

The survey, which must be conducted by a certified HERS professional, examines your home’s construction and systems:

• Ceilings and roofs
• Exterior walls, both above and below grade
• Attics, foundations, and crawl spaces
• Garage and basement floors (over unconditioned spaces)
• Windows, doors, vents, and ductwork
• HVAC, water heating system, and thermostats

A score of 70 indicates that your home is 30% more energy efficient than a standard new home. U.S. Department of Energy estimates that an average resale home has a score of 130, meaning a home that is 30% less efficient than the standard.

The program was developed by RESNET (The Residential Energy Services Network), which created the training and certification standards for HERS Raters and Home Energy Survey Professionals. Look for a RESNET qualified home energy professional to conduct a HERS survey.

What this means to you: The lower the HERS score, the greater your energy savings. A score of 80 or below might qualify you for an energy-efficient mortgage and increase your home’s resale value.

ENERGY STAR. The U.S. Environmental Protection Agency developed this program in 1992 to assess the energy efficiency of products, systems, and even buildings. ENERGY STAR certification can be awarded to anything from a major appliance to a light bulb, from your central air conditioning system to a ceiling fan. Even those strings of holiday lights are measured for energy efficiency. Your home’s electronics account for 21% of your annual energy usage, so all those televisions, external power adapters, printers, and small appliances account for a significant amount of the overall expense. Compare that to your major appliances, which constitute about 12% of the annual usage.

ENERGY STAR certification is awarded after a third-party organization tests and verifies that the product or home meets the stringent requirements of the program. An ENERGY STAR-rated home is evaluted with a HERS index, as well as other criteria.

What this means to you: The average annual energy cost for a single-family home is estimated at $2,060. By investing in ENERGY STAR products and systems, you can lower your cost and contribute to preserving our natural resources.

SEER. The Seasonal Energy Efficiency Ratio (SEER) was established by the U.S. Department of Energy to identify the efficiency and operating costs of air conditioners. SEER is a measurement of the total cooling output (measured in BTUs) divided by the total energy used for that output—similar to the MPG rating for a car. A higher SEER rating indicates a more efficient air conditioner.

In 1992, a SEER 10 was the standard, but that rating was increased to 13 in 2006. A central air conditioning system was required to have a minimum 14.5 to qualify for ENERGY STAR.

What this means to you: The higher the SEER, the greater the energy efficiency. A higher SEER will cost more to purchase, but can save you up to 40% in cooling costs.