'Telltale' is a piece of furniture that collects traces of energy (mis)use. Connected remotely to a household’s electricity meter, it responds to increases or decreases in energy consumption. Increases cause its internal structure to become less robust and, when used in weakened states, its textile surface becomes prone to flaking, crackling and wrinkling. Telltale decomposes more or less quickly — users participate in the (de)formation of an object that tells them about themselves, others and the cumulative effect of local actions. A prototype has been built and studied within two households — alterations in household actions as well as family interactions were prompted by Telltale, evolving as the object changed over time in use.