The best system would have 0 at a mild, comfortable temperature, and go up or down by 100 degrees per one degrees Fahrenheit.
But mild and comfortable is different for different people who are acclimated to different weather.
We need a defined ‘mild’ temperature. i vote for 70F/21C.
It’s a bit chilly for the warm weathered folks and a bit warm for the cold weathered folks. Seems reasonable but I’m open to suggestions.
it needs to be a range, you can’t really just have a single point, something like 50f to 70f would be good. Some people like a little below, some people like a little above, the 60s are generally pretty comfy all around though.
We also need to consider clothing as well. Which i do in this case.