Depends on whether you're in a workshop setting or just a handy guy. With a professional repair shop you have a facility, equipment, parts inventory, employees, etc. so the hourly rate reflects that scale of business. Just like with installation where you vehicles, employees, tools, parts inventory, etc.
If you're just a handy guy then it's mostly your time you're charging for.
There is scarcely anything in this world that some man cannot make a little worse and sell a little more cheaply. The person who buys on price alone is this man's lawful prey. - John Ruskin