"I too have been amazed at how little electrical power actuates these switches.
Not really. You open the valve by pushing with your finger. Then the solenoid only has to hold the valve open."
This has been one of those 'Ah!' moments, I've wondered for years how those things operated and now I know.
Now a few words of caution.
A few decades ago I was living in a shared house with some students, the idea was that we purchased a wreck of a house then fixed it up enough to sell it at a profit when we graduated, using the profits to pay off our loans. We did all of the repairs except for the gas pipes because in the interests of safety we needed a professional here. So, the guy comes in and fits new copper pipes for the gas throughout the building, he then goes down into the cellar and pressure tests the installation, the conversation went something like this:
German_EE How dangerous is this stuff? I've soldered copper pipe for the water and it was easy, gas should be the same, right?
Gasman Well, suppose there was a leak right here and the gas kept coming out until there was a layer 30cm (12 inches) deep throughout the cellar at floor level, then someone turned on the light and there was a spark. You'd take out your house, two houses to the left, two houses to the right and the house across the street. Sign here please.
I signed, we paid the bill, everyone was happy.