I wouldn't sail anymore without a auto-pilot. On our Capri-18, we had the Autohelm ST1000. Worked GREAT, sailed once to and from Catalina Island, took just over 6 hours each way and all we had was a group-24 size battery, no problems. On our C-22, we bought the ST2000 model due to the faster response time. Works better keeping up in following sea's. Just returned from an 8 day trip and we were under the Autohelm for most of the 217 miles during the trip. Power useage fairly minimal, we have a group-27 size battery on the boat with a limited battery charger on the Honda outboard. We motored 9 hours across to Catalina Island runing the Autohelm, VHF, and GPS, and the battery was fully charged upon arrival, (the Honda maximum output is 3 Amps according to their spec's). Hope that helps....
Don