Overunity – Simply means you get out more energy than you put in Comes from when you divide the amount of energy output by the amount of energy input and you end up with a figure greater than 1.
In physics (and elsewhere) “unity” is another name for 1
It is confused with perpetual motion because the idea then is that you could connect an over-unity device’s output to its input and then it would run itself.

Perpetual Motion – A hypothetical machine that can do work indefinitely without an energy source (exists in isolation). Often
Confused with overunity.

It is normal to express this coefficient as the ratio of energy output to energy input, rather than use temperatures, as shown below.

COP  =  Q   /  W

COP         =          coefficient of performance
Q              =          high grade energy output (kWh or kJ).
W             =          electrical or mechanical energy input (kWh or kJ).

Typically, a heat pump operating from a source temperature of 5°C and designed for heating only would have a COP of about 3.0, whereas a reversible machine for the same conditions would have a COP of about 2.6