How reliable is site electricity?

Chrisl300

I am new to caravanning.  I use a CPAP machine, (a mains-powered compressor medical device to help me breathe when I am sleeping).

If the power trips out overnight it's going to wake me up, and can leave me with a day-long headache. If I had to wait till morning for the electric to be reset I could be left too tired to drive the next day, or at least leave me tired and irritable.

So I am wondering, how reliable are site electrics? If they trip how long does it take to get them back on again?