yes, 120v is more than enough to maintain temps.
step mashes will be slow.
my RIMS tube is 1600W.
I was mashing at 1.5qt/lb.
I was using an insulated mash tun in FL (think 80*F - 100*F ambient).
recirculating with a little tan solar pump, it would take me 10 minutes to raise the mash tun 10...