Yes, definitely install a 30 Amp service for your Hi-Lo ... especially if you want to run anything in addition to your AC which is on a 20 Amp circuit breaker in your Hi-Lo, your Refrigerator is also wired on a 20 Amp circuit breaker ... at least they are on my 2207.
Thus you are safe running just the AC or the Refrigerator on a 20 Amp Garage Circuit because you can not push more than 20 Amps through the Hi-Lo circuit breakers for a significant time or the Hi-Lo circuit breaker will POP. Now if your extension cord is 500 ft long and only 16 gage you will lose some of the 120 Volts over the wire (called "IR" loss in the text books) causing the wire to heat up and voltage starve your appliance(s) ... not a good idea.
Until the budget allows for that 30 Amp service installation, invest in a good 12 gage 25 ft extension cord (about $50.00 at Home Depot), park your Hi-Lo close to the garage, use a 20 Amp circuit without any additional load and limit the AC load in your Hi-Lo.
If you attempt to use the AC and the Refrig at the same time (chancy) turn the AC on first (because of motor startup current demand) and once it is going turn on your Refrig (only a fan and heater) and cross your fingers ... if the demand is too much your garage 20 Amp circuit breaker will pop and it will be time to ask the Wiffey for an advance on your allowance so you can pay the electrician for the 30 Amp service installation.
Good luck, you should be fine!
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