Leland, I would say as long as you are doing permitted work, and your insurance is up to date, you'd be covered. the only con of having only liability insurance is that it does not cover workers comp, that's a seperate policy through my insurance anyway. So that being said work "alone".I'm also a stickler for not allowing anyone to touch any wiring on a job i have the permit for. make sure you spell that out.
A good question for you agent. I have read that some companies don't cover work not paid for. I think the reason is some base the insurance price on the EC sales. Someone suggested in the past to charge something for this reason, such as $1.
Perhaps you should spell out your warrenty on parts and labor. Maybe the typical used car one "As-is, no warrenty". I'm sure you would make good on things if there was a problem, by why leave yourself open. An example would be damages resulting from a power outage (non utility). A basement floods, food spoil, emergency repair by other EC, etc. resulting from a defect in the electrical system can be costly. Just seems sometimes like the less you make the more things come back to bite you.