Silly question I guess,
But having and maintaining your test equipment (I'm not talking about an old beaten up multimeter).
Some EC's carry quite a lot of Test gear, like a Megger, Fault Loop tester, some even an Oscilloscope and how about them Fluke Scopemeters.
IMO you should be charging for thier use, even if it is just for the recharging of the batteries.
It takes skill to use this stuff, we are a skilled trade, we have more skilled tools than plumbers.
People pay for your expertise, not your time, that's why you are there, not to hold the carpet down.
