The efficiency of a reversible heat pump is given by Equation 16.28. Real heat pumps, ho...

The efficiency of a reversible heat pump is given by Equation 16.28. Real heat pumps, however, may achieve an efficiency of only about 20% of this ideal limit. A heat pump with this reduced efficiency is used to heat a house for which What is the lowest value of the temperature of the cold reservoir for which it makes sense to use this heat pump instead of just using electric resistive heating, which converts the input energy W directly to the same amount of heat energy

(referemce equation 16.28)