Heat sources in the home are almost imperceptible and often wasted. [o] is a witness, which allows to create a «language element» between this invisible energy and its user through the gas bill. In order to bring a more conscientious use of heat in the home, the rematerialization and redesign of the bill with a more consistent weight gives the object more preciosity. Thanks to a folding (on the back) that we place on our radiators, this witness highlights the energy and modifies our consumption to allow us to reduce it. Thermochromism such as thermal paper makes this possible. This project represents a form of resilience as its goal is to have a positive impact on an ecosystem without changing it.