I'm shopping for a new gas water heater and looking at possibly purchasing a more efficient version with electric ignition. However, I'm curious as to whether some of the savings will be offset by the electric usage. Does anyone know how many standby watts (or estimated annual KWh) are used by the electric ignition? The specific model I'm considering is linked here, but I am interested in anyone's measurements for similar type of water heaters.
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5I'd be willing to bet that it's so insignificant that no one has ever bothered to measure it. You're trading off running a pilot light 24/7 for a few seconds of electrical sparks every now and then.– StevenFeb 9, 2015 at 2:31
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If it's well designed, I would agree with you. I have definitely seen devices that leech power for no reason, however. I'm also planning to attach it to an uninterruptible power supply (typically used for computers) so it will operate during a power outage, so that will also use a little bit of power on an annual basis.– KyleLFeb 9, 2015 at 2:42
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2I second it's insignificance. If it pulled enough power to warrant measuring, they'd probably have to state in in it's energy usage. Specifically, the exact answer would vary on local rates and such. You're charged by the kWh so (simplistically but pretty close due to its efficiency) it'd have to pull 8.33A for an hour to equal ~0.16 in my area. If it takes 2 seconds to ignite you've get 1800 ignitions but I think it'd be much lower than 8A. Standby could be 0 if it's a thermal switch; if not still very low.– ChiefTwoPencilsFeb 9, 2015 at 3:36
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2Spark gaps are typically very low current devices. They use tens to hundreds of thousands of volts, but very low current. If you're worried about that level of efficiency, your pipes and the tank itself would first have to be insulated to the point that they loose no heat to the environment. Steven is right, you're using more energy to keep that pilot light lit.– Tester101Feb 9, 2015 at 12:09
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For what it's worth, I have a gas furnace that uses a resistive heating element (think: electric stove element) to ignite the gas. I imagine this thing uses a lot more than a spark generator. But still insignificant.– William S.Apr 24, 2015 at 20:10
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1 Answer
I ended up getting a Rheem XG40T12DM40UO instead. According to my Kill-A-Watt it uses the following amounts of power, depending on the state of the water heater:
- Standby, Idle: <= 1 Watt
- Damper active open/close: ~4 Watts (lasts about 10 seconds or so)
- Active burn: ~4 Watts