He means you could replace the 12 gauge wire if you had conduit.
Maybe you do. Do you know if you have conduit or is your feed direct burial?
Ahh ! ok now I get it...... Yes it is run out of the hose through conduit, then pops up right next to the garage through conduit.
The guy I had over seemed like a nice guy, but didn't really go over any options with me. He just said it would be illegal to change the double 20 to something larger, and if I ran as is, it would be too much of a draw and probably trip the breaker over and over again, and that I needed 10 guage instead of 12. He left, and I thought about calling someone else for a second opinion, but winter is almost over, so I figgure I'll just sell my heater, and if it doesn't sell, I'll get someone over when the snow melts and go from there.
It's one of those things, that I assume can be done, and be done correctly, he just didn't seem like he wanted to do it. Heck, I was paying him, it's not like I asked a buddy to come over and do it for free.