Install a sub panel inside, thats what we did. Got a used 200 amp Square D panel mounted by the door, it was full of breakers too. Check craigs list and eBay for used panels. Makes it easy to add more circuits in the shop, you feed it with one large cable, cuts down on multiple long runs of smaller wire. Since installing the shop panel my 80 gallon compressor starts much quicker. Less line loss for sure, easy access to the breakers inside the shop. The local electric company engineer and an electrician friend helped us with the design and wire sizes. We upgraded the house power too, running the electric clothes dryer, air conditioning, a lathe and an air compressor etc. at the same time was really taxing the original house breaker. Our power company hooked up additional meter can for zero cost, they charged us nothing for the upgrade. We now have two 200 amp meters/breakers feeding the house on separate cables from the transformer. We were maxing out the cable from the pole. The monthly added meter fee is cheap. Now we can add a pool and sauna someday! We don't pull the house lights down when the compressor kicks on anymore. I was expecting the power co to charge for install but, they even set a new pole and cleared brush for free. The house service is all new, they disconnected us for about an hour to run new cables to the new pole. Maybe its a rural thing, we live out in the sticks.