| This is in their FAQ.
How Does the Power-Save Unit Work?
The Power-Save reduces the amount of power drawn from the utility by storing (in its capacitors) otherwise lost electricity (watts) caused by the inductive motors in your home. (Some examples of inductive motors are Air Conditioning units, refrigerators, freezers, washers, dryers, dishwashers, pool pumps, vacuum cleaners, furnace blower motors, fans etc.) The technology applied by the Power-Save 1200™ Unit supplies that stored electricity back to your inductive loads, thus causing you to decrease your demand from the utility. If you decrease your demand from the utility, your meter slows down, and you use less electricity. The thought is, you’ve already paid for that electricity, why pay for it and waste it when you can pay for it, store it, and reuse it again. This whole process is called power factor optimization.
and...
What is Power Factor?
Power factor is the percentage of electricity that’s delivered to your house and used effectively, compared to what is wasted. For example, a 1.0 power factor means that all the electricity that’s being delivered to your home is being used effectively for its purpose. However, most homes in America today have a .77 power factor or less. This means that 77% of the electricity that is coming thru your meter at your home or business is being used effectively, the other 23% is being wasted by your inductive load. With a low power factor, the utility has to deliver more electricity to do the same work. However, the Power-Save unit increases that power factor in most cases to .97 or .98, thus increasing the effective use of your electricity and lowering your usage.
i attached the US DOE report explaining power factor | 
