The measure really is how many joules of energy is required to heat something a certain amount of joules. By burning oil or converting electricity to heat, 1 j

The measure really is how many joules of energy is required to heat something a certain amount of joules. By burning oil or converting electricity to heat, 1 joule of stored chemical or electrical energy converted to heat energy will raise the heat of that something by a maximum of 1 joule. A maximum of 100% efficiency. By using 1 joule of energy to compress cold gas into warm gas, we can raise the heat of that something by 3-4 joules. Moving heat energy around is more efficient that generating heat energy. Commercially available technology 300%-400% efficient.