Why is energy efficiency the most abundant, cheapest way to reduce greenhouse gas (GHG) emissions?
Anywhere energy is used, there are opportunities to increase efficiency. In most cases, energy efficiency measures will pay for themselves over time in the form of lower energy bills.
How quickly they pay back their investment depends on a lot of factors, such as the cost of energy, and the overall use of the measure—for example, how many hours an appliance is on. Weather is a factor when the measure is related to maintaining environmental conditions—in air conditioning, heating for example.
Economic analysis of the cost of various energy efficiency measures, compared with that of building various types of energy sources that emit less GHG than fossil-powered plants, shows that most energy efficiency measures are cheaper, and therefore pay for themselves faster, than most kinds of energy generation.
Here's an example of this type of analysis:
Reducing GHGs substantially—enough to slow down climate change—will require many different approaches, including both energy efficiency and renewable energy, carbon-neutral transportation fuels, and possibly storing GHG emissions safely away from the atmosphere.
Over thirty years of experience shows that energy efficiency is the most abundant, cheapest, fastest approach that we have right now. And the technology exists now to implement efficiency at many different scales, from your own house or apartment or car to large office buildings and industrial facilities.