Gas + Electric

I'm trying to build a partial e-herms where my system is partly gas and partly electric. This is the beginning of an eventual switch to an all electric computer controlled herms. Currently, I'm heating my HLT over gas, but I'd like to add a heating element so I can control the temperature during the mash. Since I don't have a 240V outlet with enough space around it, I'd like to install the highest power element possible that I can eventually switch out to a 5500W element when I move to a house with an outlet for it. I'd wire a new outlet up myself, but I'm renting, and I don't think my landlord/roommate would appreciate it very much. Any suggestions for 120v heating element that can be swapped when I'm ready? This would be a weldless addition.

I was running a gas/electric in the garage awhile back and I used a 120v 1650w heating element in the rims tube. If you have a 20a 120v circuit you could get away with a 2000w element max. When you say "swapped", if you mean same hole size as a 5500w, then yes all screw in residential hot water heating elements are standard.

Exactly what I was looking for. Thanks for the response.