Hybrid - Heat Pump / Cheaper to operate than Gas in SoCal?

If someone offered to pay for the install of either a Hybrid or a Natural Gas Heater, which one?

  • Hybrid/Heat Pump 50 gallon

    Votes: 0 0.0%
  • Old School Natural Gas 50 gallon

    Votes: 0 0.0%

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Wandering_Burr

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I am looking at replacing my 50 gallon NG Water Heater and aside from the up front costs of electric/condensate line/capping the gas and vent (which are not small), the EPAs calculators appear to show a significant savings over ten years versus Natural Gas. Despite my searches this topic doesn't seem to come up so I am here to get a sanity check.

First the basic check of the US Govt Energy Guide sticker. Rheem 50 gallon natural Gas (XG50T12HE40U0) $288/year. Rheem Hybrid (XE50T10H45U0) $104. So ten years is a $1804 savings using national averages on use and utility pricing.

Plugging in my local pricing using the formulas here https://www.energy.gov/energysaver/...cy-storage-demand-and-heat-pump-water-heaters
using my SDG&E blended rates of $1.90/therm on gas and $0.29 for kWh I get between $1050 and $4500 savings over ten years depending on how much my solar array contributes.

Family of four in a four bath house and one oversize tub. We never have had issues with hot water even with large populations of guests. Would run the Hybrid at 140 with a tempering valve and think we'd be ok with supply but this is mostly based on others online saying it supplies enough water.

SDG&E gives a $500 instant rebate and Feds give $300 so a Rheem 50 gallon unit would be a couple of hundred less than a NG one out the door. So if installation costs aren't outrageous seems like the way to go.

Better for the planet. Cheaper to own over time. If I run it at 140 degrees seems like the rate of recovery would be good enough to keep us ok for 3-4 showers over a couple of hour period. What am I not considering?
 
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Reach4

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What am I not considering?
For rates, you want to use the marginal cost rather than blended, unless you would discontinue gas service if you got rid of the gas water heater. There are no blackouts with gas, although many of the newer WHs require electricity to operate.

Marginal electric rates in California are often higher than blended rates, aren't they?

I did not check any of your numbers.
 

jadnashua

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An electric WH, whether just resistance heaters or hybrid version, have lower standby losses because there's no uninsulated flue running up the middle. The recovery rate on a NG WH will be considerably faster than a hybrid, and if you use a lot of water, the hybrid tends to turn on it's resistance heaters, so you don't get the multiplication factor from the heat pump. In resistance mode, 1W in, 1W goes to heat...in hybrid mode, is more like 1W in, 3W heat to the water, give or take a bit. So, your hot water demand volume and schedule can make a big difference in your total efficiency. The goal is probably to have that tank large enough so that you'd never trigger the backup heater to be needed.

The hybrid WH will also cool the space, as that heat needs to come from somewhere, which could lessen the heat load and save some on a/c costs, but in the winter, if you're running the HVAC for heat, you may need a bit more to compensate...depends somewhat on where all of those devices are. A typical furnace room tends to be warm, and that waste heat ends up in the tank of a hybrid system.
 
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