I have zero experience to go on but if row covers, wall of waters and cold frames allow people to get a early jump on the season, then I don't see why a heated Earthtainer with top wouldn't do better than those. Well I guess that's assuming that you insulate the containers a bit.
A couple things I think will be worth looking into:
- Some kind of variable vent for the IncuTainer so the temperature can be controlled a bit.
- A plastic cover for Ray's new pea fence supports to allow increased warmth after the IncuTainer top has to be removed.
I should do some experiments this winter to test the thermal performance. I just need to track down the right containers, I seem to find everything but the 31 gal Rubbermaids that Ray recommends and with the pea fence supports the size will be more important to get right.