I am actually optimizing my heating and it would be really helpful to have a temperature average overlay for the energy dashboard to have it at a glance.
Furthermore, it should be possible to add not only one temperature, since most heating systems provide a calculated ambient temperature considering the building time constant depending on isolation.
I would also find it very useful to have a temperature overlay. Something like in the sketch I whipped up. It could even be a toggle to show/hide (as I find it mostly useful during the cold seasons).