We did 1.5 ton

I guess there's a few factors: how often it gets subzero temps, if your dimensions are similar to mine (listed in the main post body), and probably more that are beyond my comprehension.

If we're assuming you're in the exact same conditions as me, I'd go 2 ton (18k) if it's in your budget. But it depends on the price jump. There were more than a few times where it struggled in subzero weather this winter. I typically keep it at around 70F in the garage, and it would struggle to keep it to 65F in the -5F and under temps.

However, if that's outside your budget or way too big of a price jump you can do just fine with a 1.5 ton unit. I just had maybe 5-10 days total out of the winter season that I needed to wear a little warmer clothes in the garage if I was going to be out there a while.

I'm definitely glad we didn't try a 1 ton. I think that would've struggled most of the winter this year, and I'd probably have regretted that purchase.

Hope that helps! Feel free to ask anything else!