OK, your setup is different than mine (not surprising since mine is 2007). I also have 2 switches, but neither has a light. The light for gas not igniting is between them.
So, I wonder if a prior owner did a bad wiring job on yours? The electric should most certainly not heat the tank if the switch is off. That's a good way to burn the element out if the tank is empty. AND, since the switch itself lights, I'd say it should be lit when turned on, and not lit when turned off. That just about makes me think the gas switch should be lit when gas is turned on to heat too. And, it should be unlit when turned off.
I haven't been able to find a wiring diagram that shows that setup. But, this kind of switch is commonly found in an automotive store, such as Checker, Pep Boys, etc. It's a lighted rocker switch. It would probably come with wiring instructions that show how to connect the light DC feed and the circuit you are controlling. It is probably a DPST kind of switch.
I'm going to guess you could look at the wiring colors at the hot water tank to figure out which wires at the switch end turns on the heating for electric and gas. I believe the ground (at the tank) will be white for both. There would probably be identical wires at each switch position. There would also be a battery feed for each switch and I suspect they would have a common, but different color than the ones at the tank. A third wire you should see at the switch area would be for the lights.
It's also possible the OEM switches were never lit in this setup. In that case, you'd have only two wires at each switch position (battery feed and tank load) and you'd install a SPST type switch. However, thinking about this, I believe there ARE SPST switches with internal lights. If you had only two wires, these would light when the circuit is on.
Here's a link to an explanation of these kinds of switches, in case I'm confusing you. (I may be confused too, *grin*):
https://www.littelfuse.com/technica...ehicle-technical-center/poles-and-throws.aspx
Edit: I AM confused - see Post #6!
- Jack