Present Outdoor Temperature = 40 F
Present Indoor Temperature = 75 F
Present Temperature Inside Freezer = 5 F
Tw = Temperature
Difference between Window Freezer's evaporator (inside freezer) and condenser
(outdoor)
Ti = Temperature
Difference between Indoor Freezer's evaporator (inside freezer) and condenser (indoor)
Energy Savings Rate H = 1 - ((Tw x Tw ) / (Ti x Ti))
H = 1 - [(40 -5) x (40 - 5) / (75 - 5) x (75 - 5)] = 75 %