We recently bought a new to us home that has 2 gas water heaters and one electric water heater.  The master bathroom wing (sounds stupid I know) has one gas and one electric water heater in the attic above and the wing with the 2 guest bedrooms/baths, 1/2 bath and laundry room has another gas water heater.

I'm getting quotes to have a transfer switch installed to power the 7kw gas powered generator that we just bought 2 weeks ago.  

I'm trying to figure out if I need to plan for any power consumption to keep the hot water flowing in the event of a power outage.

So does my gas water heater require any electricity to operate?

Maybe



http://www.cleverdude.com/content/8-benefits-of-electric-water-heaters-over-gas-water-heaters/

Check and see if they are plugged in/ wired.  Most water heaters are power vent models, which require electricity. Some older ones had pilot lights and required no power.

Also keep in mind that even the old ones used electric thermostats.

Well I do know for sure that the pilot light is manually operable because we had to go up and re-light it last weekend.  We're on city water so no well or pump to supply water.

The old ones had thermoelectric pilot controls. The heat from the pilot flame kept the safety shutoff open. If the pilot went out the valve closed. These heaters, still common today, require no outside electric power source. The cost to run the pilot is probably less than the cost to run power to and operate the electric ignition.

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mine has an AC powered vent

does it have a cord?  that there might be a big clue.  ive wondered about mine as well, but have been too busy/lazy to look.

Nothing obvious but I didn't check behind it.

I have a new gas water heater that uses no electric (uses pilot light, has manual built in igniter).

Even if it requires electricity I would imagine that the load required would be rather small, so your generator should have no problem powering the electric portion of the gas water heater.

As others have said maybe. Depends on the unit.

I know mine does. It was nice to have at least a hot shower when power was out.

3 water heaters in one house though? I wonder what the hell they were thinking?

Just replaced mine.  No electricity at all

Doesn't the pipeline system that delivers the natural gas to your house require electricity?

mine is 3 years old and needs no electric either

I have a gas, power-vent model and was able to easily run it during a recent power outage from a deep-cell battery and 400/800 watt inverter.

I used to work for a major water heater company providing tech support to plumbers and hvac techs.

Gas water heaters don't use any electricity at all except for powervent as someone else said but they aren't the most common at all they're actually so uncommon we only had about 10 people dedicated to that type but about 600 people for standard direct vent. They also cost about twice as much as direct vent.

Also the ignition system isn't powered at all even if you have the new smart gas models that actually have a computer on the front that gives off codes. The pilot powers the computer, when it goes out so does the computer.

The igniter, like I said, is self powered and sparks when you click it. We actually removed them and used them to shock each other around the office. And I still have a few that I mess with my wife and kids with and one in my go bag for fire starting.

If you have a power vent you'll have a blower looking thing on top of the water heater so it'll be fairly obvious. A generator should be able to power that though as it doesn't use much power.

Word of advice also, all gas water heaters below 75gal are sealed combustion and have a vent on the underside of the heater called a flame trap. That needs to be vacuumed out once a month otherwise the unit will shut off. That's this biggest problem everyone had so I figured is throw that out there lol.

Oh and multiple water heaters are common in large houses that have to run alot of water lines where the water might cool before it gets to the bathroom or sink. Pairing electric and gas is weird though.

Bottom line gas water heaters use no power at all what so ever even the ones with smart boxes, unless its a powervent.

That's how mine works... the one that was in the house when I bought it blew up 3-4 years ago and the replacement works the same. There's no electrical wiring anywhere near the water heater.

Possibly.

EPA regs that changed @ 2006 or 2007 made it extremely difficult for gas companies to get permits for gas powered turbines to pressure the gas pipeline.

Newer pressurization stations are likely to have electric power from a utility provider.

Remember the power supply issues in TX last winter?  Followed closely by a natural gas shortage in NM?

Muni water supply may also be dependent on electricity depending where you live.  Not all have back up generators for water delivery or treatment.  YMMV

my tankless has a little dynamo that powers the ignighter when the water flows through it . no power vent either . So long as I have water pressure and gas I have hot water .

mine will

yours may or may not

look for a power cord

I have (3) 'Paloma' on demand propane fired water heaters, they work without electricity.
the oldest has been in use since 1989, no problems.