"Zapped" Your time on site is irrelevent regarding what you charge. You have tools to buy, gas, truck repairs, insurance, blah, blah & blah to pay for to stay in business.
We charge a service call fee of $85 which includes up to one hour. That hour includes travel to the job. However if all we do is reset a breaker or such have only 15 minutes invested I charge a $55 "Limited" service call. There is more to everything than meets the eye, ie office people keying in your mans invoice data etc.
If you feel you are ripping people off charging them $85 for twenty minutes driving and twenty minutes work you need to get a job and give up contracting.
You are providing a service to people and could save someones life or burn their house down depending on your workmanship. Your work demands more than a landscaper or roofer and you need to charge accordingly! Just don't rape people just because you can.