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Does anyone know a way of calculating the energy needed to heat a home/room? (feddit.uk)

submitted 10 months ago by [email protected] to c/[email protected]

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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.

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[–] [email protected] 2 points 10 months ago (1 children)

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.

[–] [email protected] 2 points 9 months ago

Thanks for your response.

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.

That was my original idea and it actually works pretty well, but since the cost of power spends most of the day at industry average rates electric heating gets pretty expensive which is really what I'm trying to minimise.

One thing you don’t mention is whether you have any way to store heat

I don't, but I really, really wish I did. The place I'm in is rented so I'm loathe to make big changes like installing storage heaters (installing relays in the walls behind the current radiators doesn't count, shush) but I had old-fashioned, 1980s storage heaters exactly as you described in my old place and I loved them for the exact reasons you described. They weren't active with a fan, but even just having a very heavy, very hot thing in the corner of the room was enough to maintain the temperature and given my electric rates regularly get below 5p/kWh and sometimes even go negative overnight my heating bill was basically negligible. Consider me a member of Team Storage Heaters.

As you suggested, what I'm trying to do is turn my walls, floors and furniture into the thermal mass of a storage heater, by making them toasty when it's cheap in the hope they'll keep the room slightly warmer when it's expensive.