I have am looking for space in my circuit breaker panel to do an upgrade. There is a 30 amp dual pole breaker labeled "water heater". Our water heater was upgraded to a tankless about 6 years ago and has a standard 3 prong power cord that plugs into the wall. Does that mean that the 30amp breakers are free now, or does my water heater use both the plug (maybe for the controls; that would seem odd but my old water heater didn't have digital controls). On the other hand, I don't remember the old water heater having any electrical components. The old water heater had a tank, and was installed some time before we moved in 15 years ago, though I don't recall the age.

Is there a way to figure out if that 30 amp circuit is being used? We turned it off and nothing seemed affected; the water heater still seemed to work. But maybe there is some internal component that is directly wired?

  • I should add that both water heaters were gas. It's likely the old water heater was not original to the house, which was built in 1976. So it's possible that there was an electric water heater before the gas model was put in?
    – Tami
    Commented Dec 11, 2014 at 1:36
  • Neither a gas tank or tankless WH would need 30A@240V. A gas tank WH without digital controls typically has no electrical hookup.
    – DoxyLover
    Commented Dec 11, 2014 at 2:08
  • 1
    Keep in mind the label might be wrong. Do you have central AC or electric dryer or stove that might be using it instead?
    – Grant
    Commented Dec 11, 2014 at 3:46
  • I do have central air. It has a circuit outside though. Would it have an additional circuit inside? The dryer is gas. Oven is electric, so I'll check that, but I am almost positive it's on a different circuit. <em>almost positive</em>.
    – Tami
    Commented Dec 12, 2014 at 4:08

1 Answer 1


Yes, it seems quite probable that there was an electric water heater at some point, and if the last two were gas, that circuit is probably unused. Leave it off, and check for anything not working; and/or follow the wires if visible, or look for a junction box near the water heater location that has a cable going in and no wire coming out.

  • 1
    Just a follow up, but we never found anything that seemed to be connected to it. I am assuming at one point there was in fact an electric water heater that was replaced with a gas water heater. I also found one more circuit that doesn't seem to go anywhere. However, there was no evidence of a capped off electrical system, so I'm not sure where the wires went.
    – Tami
    Commented Apr 10, 2015 at 0:37

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