Cost savings from efficiency gains are at the core of the green building business case. Significantly lower energy bills are said to be a major factor in the green rent premium observed in earlier studies. Our study tests this relationship by inferring energy costs from operating expenses for a large dataset of U.S. office buildings and relating them to rental rates. We find that eco-certification is associated with a higher than anticipated total energy expenditure, which is the opposite of its expected effect. While our dataset does not contain a direct measure of actual energy consumption, this result puts the cost-saving argument into question. By contrast, we confirm earlier findings of a green rent premium but it might be an effect of factors unrelated to a tenant’s operating expenses.