I am very familiar with HRV/ERV units (15 years commercial HVAC distribution experience).
They are useful for tempering outside air with exhaust air energy, typically used in all designs to meet the ventilation requirements for occupancy.
If you had to temper your inlet air (and had a pretty significant volume you were dealing with) they would be a useful energy recovery device. For most non-commercial rooms there may not be enough benefit for the cost.