Charging by the hour is tough. You make more when you bid jobs right? So why not bid all of them? A good transition would be to stop charging by the hour for anything other than troubleshooting. Once, you get a feel for biding service calls and repairs, go flat rate on troubleshooting as well.
For residential and some commercial we use flat rate, better known as contract pricing, flat rate is just a fancy twist on words, and misunderstood by many, because not many know how to apply flate rate pricing, they think there is some magic book that they pull a price from, when in fact the books are just guide books, not price books, once you learn how to master the guide books to arrive at an on site quote you on you way to sucessful pricing and winning more jobs at better then average earnings.
If you looked at any service business with trade skills, you would discover their average service rate is somewhere from 150 to 200 an hour, and many have dispatch fees that range from 39 to 99 and most of hese are small guys from 1 to 4 employees, not large at all, they are easy to find, they have professional lettered trucks, professional yellow page ads that stand out, and they stand out as neat and clean when they deal with the customer. It takes the same effort to work as one of these guys as it does plugging along just making it, the only real difference is a willingness to learn more and earn more.