In Austria and recently (since April?) there is a provider called Awattar. They sell energy with a flexible price model that's based on the energy spot market.

In Austria and recently (since April?) there is a provider called Awattar. They sell energy with a flexible price model that's based on the energy spot market. They claim "you might even get paid to consume power". My car charger can interface with them, and do exactly what you suggest. In theory you "just" need smart controllers for the systems. The idea is similar to 1980s "Storage heaters", which would use cheaper nighttime power; but using fossile electricity this is very inefficient and thus bad for the environment - when exclusively using excess regenerative energy that's different though. Same for AC. The problem is when there is no excess energy for a long time; so I'd personally go with a hybrid system for heating (regenerative energy when available for a heat pump, local solar thermal energy for "base load" heating/warm water - not sure if fossil fuel for winter is necessary with that, but that depends on your climate).