Rental properties are ‘energy deficient’: the lack of energy efficiency places a burden on renters in the form of increased energy expenditure or harmful indoor temperatures. This report estimates the monetary value of this burden by calculating the worth of the thermal energy that energy deficient rental properties lack. Drawing upon six years of real estate data, we calculate the annual burden of energy deficiency in the ACT to be $39 million. The burden is particularly heavy for vulnerable renters, such as those on a low-income or living with disability. This analysis strengthens the arguments for minimum energy efficiency standards for rental properties.