Hi kitana, sorry I missed your post earlier.
In my case, this seems to be cheapest/most predictable method, but your conditions may vary as you're a good bit further south than me. I used to thermostat before the dome, uncovered, and at the time I felt it was just the same as tinkering, but I'm not so sure now. Its hard to tell because the cover also makes a big difference.
What I've settled on so far is as follows:
Right now, night temps have been in the 20s and day temps hovering around 30 mark.
To get back up to 95 degrees for physio by 7:30, I needed to run heater from midnight to compensate for days prior loss. Before this week, i had it scheduled fir 1:30 am, but it wasnt quite getting to temp as the temps dropped further. I achieved the desired heat in that time...but leave heat running til about 9 am because its nice to have the jets have warmer water while I'm In when the temps are lower.
Inside the dome right now, the air is about 52 degrees, but it was closer to 40 when I got up in the dark
My timer shuts down the heat and my schedule slows the pump rpm at 9 am. In 3 hrs I've lost about .9 degrees, but if I feel like a swim later, I'll just manually override the time on my remote and start heating because 92-94 is still okay for a regular swim. If I'm having people over for a night swim, I'll run it up a bit more beforehand.
I guess if you were Thermostatting to a particular temp, you might end up using the same amount of energy, but then you're also having to leave the pump at higher rpms. I could maybe try this for a day and compare energy use roughly to see.
The speed of heat depends on the btu of your heater, the gallonage and the air temp differential.
In my case, I do lose some extra heat when heating because I divert the water from one of my 3 returns and run it through the air warmer unit you can buy with the package. In my climate, attempting to keep the in-dome air above freezing is important or the zippers freeze and its hard to get out. That happened once or twice to me on sub-zero days
But the effect of running the warm water through the coil s the equivalent of a chiller, so that reduces my heating capacity and retention.
Enjoy and et me know what you find from any experiments. I might see what happens tomorrow if I thermostat.
you could generate you’re own personal cloud inside the dome :angel:
