I just don't want to say something that is way too low for that work.
Who decides what is "too low?" If your shop rate does not cover your overhead plus wages (including your own), that would surely be "too low," because you are below your breakeven point. On the other hand, if your overhead and wages are covered, and you have included a profit margin, can anyone else tell you that you are too low? Perhaps you are just more efficient. There is nothing wrong with that.
If you must add one-time expenses because installation is not part of your routine, I would think it unlikely that you are going to seriously undercut the prices of others. This is especially true if you remember to include all the time associated with an install. For example, if you rent a lift, the cost of the rental is not the only expense. You may need to go get the equipment and then return it. If that adds an effective two hours (or whatever) to the job, it may be unlikely that you will be too low on the selling price. And what about loading and unloading your truck? This is part of installation time, too, right? And then there may be time involved to procure a permit, in addition to the cost (and markup) of the permit fee. If you drive to city hall and kill an hour on the permit, somebody needs to pay for that time, right?
Liability insurance may be the main thing you should worry about, as others have mentioned. Your accountant may advise that you carry liability insurance whether you do installations or not. In some of my early years, when everything I did was "cash and carry," I believe I still had some kind of minimum liability.
Insurance is a monthly expense, of course. So it is part of overhead and will be part of your hourly shop rate.
Unless...you can get insurance on a job by job basis. You know, like flight insurance. Is that even possible?
If someone tells you that you are "too low," ask them why they say that. After all, there are no pricing police. If someone is simply annoyed that you are cheaper than they are, that's not necessarily a cause for concern, unless the one telling you that you are too cheap is your accountant. Of course, it can be helpful to know if your prices vary significantly from your competition. For example, if you are routinely half the price of your competitors, you should know why. Is it because you don't mark up materials, or because you pay yourself a small salary, or because you have little or no profit margin? Knowing why can make you smarter at pricing.
On the other hand, mindlessly charging what others charge (not that you do this) is not a good business practice. My accountant calls it a form of Russian roulette.
The main thing, though, is to have fun.
Brad in Kansas City