Probably marginal at idle. You've got the condenser fan load, the evap fan load, and the clutch on the compressor. This assumes an electric fan on the condenser. But if you put a volt gauge in (or have an ammeter), you can always turn it to low or off if your stuck for an extended period. Moving, with the engine speed up, you'll be fine. A/C and power accessories had a lot to do with the change from gen sets to alternators.