Does anyone know a way of calculating the amount of heating I need to maintain an average temperature in terms of kWh of heating per 24 hours? Ideally one taking into account weather conditions.
I have a pretty big Home Assistant setup which includes switches for individually controlling all the (electric) heaters in my home. I’m also using an electricity supplier that changes the amount they charge every 30 minutes to reflect supply and demand. Given these rates are published at least 24 hours in advance I can currently choose a number of hours to run the heaters per day and have an automation automatically select the cheapest periods. I’m paying less per kWh for heating than I would if I was using a gas boiler. Plus, it’s all from renewables, so working out that number of hours is the next step.
Why not just use standard thermostat functionality: set the target temp a bit higher when rates are low and a bit lower when rates are high. It won’t be perfect but it’ll stay more comfortable and you don’t have to over complicate things.
One thing you don’t mention is whether you have any way to store heat, to even out the times when your heat is off. Some of this is thermal mass in the room and maybe that’s all you can do. My parents house when I was a kid had thermal storage radiators that worked really well. The heating elements were on a timer, so only came on overnight when rates were lower, but only heated the bricks or oil or whatever storage medium was inside. The radiators were essentially an insulated box so were cool to the touch. Then, during the day, the thermostat simply controlled a fan circulating air through the radiator to pick up heat as needed.