For over a century, New York’s Residential Heat and Hot Water Code has controlled the distribution of heat in New York City. Established in 1918 by New York City’s Department of Health, it mandated that all residential and office spaces in the city be heated to 68 degrees Fahrenheit at all times. Changes to it in the ensuing years not only sought to protect New Yorkers’ health but reflected pressures in New York’s fuel economy, which experienced periods of shortages and a transition from anthracite coal to oil that started between the two world wars. Consequently, the standardization of 68 degrees Fahrenheit reflected shifting assumptions about health and the “right to heat” for different communities over time, and the practical need to ensure affordable fuel for the city’s population. The Heat Code, accordingly, played a crucial role in shaping energy consumption in New York and helping to formulate an “invisible energy policy”—that is, a policy developed in non-energy fields, such as health and housing, that alters energy usage in important but inconspicuous ways, with important consequences for the environment and for social justice.