Good enough for a fan, furnace, and AC setup. What we need going forward, though, is something that can intelligently use heat pumps to take into account electrical costs, current rooftop solar generation (if any), and the heat pump’s efficiency ratings in order to most efficiently balance between the heat pump and a regular furnace. Can choose the balance between either cheapest way to run or the least amount of CO2 (which won’t always match up). May also have to consider multi-stage setups where you can run it at low/medium/high levels.
I don’t think it’s impossible for a FOSS solution to do this, but I don’t think anyone has tackled it, either.