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Thread: replace gas with electric water heater

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    DIY Junior Member young707's Avatar
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    Default replace gas with electric water heater

    I have a leaking 40 gallon 40000 BTU/hr gas water heater in garage open area, at home for 2 adults in San Jose, CA.
    I am looking into to replace with 40 gallon 4500W electric water heater.
    So I need to run 220AC extension for around 5 feet, wall socket, and breaker. I also like to add shut off timer so that I only run the heater 12 hours instead of 24 hours every day. So far, I do not find this timer at Home Depot.
    What kind of work time and approximate cost for electrician to do this work?

  2. #2
    In the trades Dana's Avatar
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    Replacing it with another gas HW heater would have far lower operating expense than an electric HW heater in your area (unless you went with a heat-pump hybrid type at much bigger upfront expense, in which case the operating costs might be comparable.)

    Turning off an electric HW heater for 12 hours/day with a timer has almost zero impact on the amount of power used. Electric tanks have very good insulation and very low standby loss. To get a significant reduction in standby loss and savings would require a big drop in the water temp during the "off" period, but an electric tank set to ~125F would typically lose less than 1/4 degree per hour, so you'd still be over 120F at the end of your 12 hour period. The vast majority of the power use is for raising the 55-65F incoming water up to the 120F-140F setpoint temp- the difference in standby power use between water with less than a 5F average difference is truly in the statistical noise- low single-digit percentage savings on the overall power use at best. Only if you can get a rate reduction on your electricity bill for heating water only during off-peak hours would a time-of-day approach make any economic sense.

    Whatever heater you install, you get pretty good payback on 5/8" wall closed cell pipe insulation on all the near-tank plumbing (including the first 6-10' of the cold-feed closest to the heater and the temperature & pressure overflow valve & outflow plumbing), as well as any hot water distribution plumbing that is accessible. For a primer on how to do it, see: http://www.leaningpinesoftware.com/h...er_pipes.shtml

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    DIY Junior Member young707's Avatar
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    Dana, Thank you. Please help me with rough estimate comparison between gas & electric water heater.
    In San Jose area, 2 adults, single family home, hot water usage is roughly around (shower + faucet + dish washing + laundry ) 32 gallons per day, is this number close, or I should use half for heated water?
    How much cost between gas & electric water heater operating cost?

    So, in this areas, you think 12 hours shut off timer will not save much in energy?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Shutting off an electric WH via a timer will cost more to install than you'd likely ever recover...it just doesn't cost much to leave it on. With the insulation, with no use, the tank just doesn't cool off enough to require it to turn on much (if at all) during that 12-hour period. Now, if you lived in say northern Minnesota and had the thing in a garage that got to just above freezing most of the winter, that's be another issue, but then, if you did turn it off, it would likely freeze the lines!

    1KwHr = 3400BTU
    1 Therm of NG = about 100,000BTU

    Now, the NG WH isn't as efficient as electric, but say the electrical unit ran for 1 hour/day = 40000/3400 = 11.76KwHr.

    If the NG WH had to run an hour, with the same sized burner, it would use about 1/2 a therm - giving that it isn't as efficient as electric. Some designs are better, some are worse.

    Price your electric and NG and you can get your localized numbers. Around here, that 11.76KwHr would cost around $2.11 verses a 1/2-therm of NG for about $0.75. Do you really want an electric WH? If you had to run a new gas line or even start up a new service, that initial installation cost could be quite a bit, but since it's already there, it rarely is more cost effective to go electric when NG is present.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member young707's Avatar
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    understand.
    So you are saying, given same amount of heated water, electric will cost 3 times more compare to gas, correct?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    That's true where I live, but we have high electric rates...your results may differ. You can easily tell by looking at your bills and comparing. Plus, typically, a NG WH will have a quicker recovery rate, and if you do need even faster recovery, you can get one with significantly larger burner. A larger burner just needs to run less time - that doesn't mean it uses more (although it may, but it's not linear). Whle you may not use a lot of hot water, a fairly typical use pattern is lots all at once...the same sized electric may not be large enough as a NG one. Having more available, though, may tempt you to use more.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member Runs with bison's Avatar
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    I agree with what the others have noted. I'll add this: with nat. gas prices very low for the past several years and electric rates rising, the one time I can see switching to electric making economic sense is if your only use of nat. gas is for water heating. If you can shut off the gas altogether, then getting rid of a high monthly fixed cost for being connected to the nat. gas grid could easily pay for the additional electricity cost.

  8. #8
    In the Trades Gary Swart's Avatar
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    Where I live, electricity is quite reasonably priced. That said, natural gas is far more economical. I would suggest a water heater that does not use a standing pilot light.

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    In the trades Dana's Avatar
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    Without your actual retail-delivered electricity and gas rates it's hard to say how much more the electric tank will cost to run, but unless you have 5 cent electricity or $2/therm gas it's definitely less expensive to heat hot water with gas than electricity.

    At a buck a therm gas (typical US average- yours could be more), in a hot water heater with an EF rating of 0.60 (not the highest, not the lowest) for every buck of fuel you get (100,000BTU/therm x 0.6=) 60,000 BTUs of heat into the water (more or less- depends on how much water you use), which is 1.67 cents/1000BTUs.

    At 12 cent/kwh electricity (about the nat'l average), in a tank with a 0.90 EF rating (not the highest, by any means) every kwn delivers (0.9 x 3412=) 3071 BTUs to the water for 12 cents, which is 3.9 cents for every 1000BTU. That's 2.3x the cost of heating it with buck-a-therm gas in a standard gas HW heater.

    If you replace the gas HW heater with a ~0.90 EF condensing version like a Vertex, with $1/therm gas you'd be at 1.1 cents/1000 BTU of water heating. If the gas lines to the existing tank are big enough to handle a 76,000BTU/hr burner (probably true, unless it's a very long run from the regulator), the installed cost of installing a Vertex would likely come in at about the same as the electric tank heater that would need the extra electrical work. There may be state and utility subsidies available for going with a condensing tank heater too, which could make it even cheaper.

    32 gallons/day of hot water would be on the low end of usage for 2 adults, but not impossible if you only take short showers, and have EnergyStar clothes & dishwashers, etc. At 32 gallons /day use the EF of an atmospherically drafted gas water heater falls off by quite a bit (they're tested at roughly twice that daily volume), but not as much for an electric tank or a condensing gas-fired tank.

    IIRC you can't even BUY appliances that have continuously burning standing pilots in California (and many other states) these days, most have an electronic ignition, even though the electronic ignition only strikes a (temporarily burning) standing-pilot that lights the main burner.

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    Plumber jimbo's Avatar
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    Quote Originally Posted by Dana View Post
    IIRC you can't even BUY appliances that have continuously burning standing pilots in California (and many other states) these days, most have an electronic ignition, even though the electronic ignition only strikes a (temporarily burning) standing-pilot that lights the main burner.
    Furnaces went electronic a long time ago. Just as of July 2012, no more standing pilot stoves allowed ( this is all Federal, NOT just CA). As far as I know, water heaters not affected yet, but I am sure it is coming! Even the ultra-low-nox ( burner looks like a flux capacitor) units mandated in several CA counties, they are still standing pilot.

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    In the trades Dana's Avatar
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    jimbo: Thanks for the detailed update on the CA-state of standing-pilot ignition! I'm a bit surprised that they are still be allowed on water heaters, given the general trend.

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    DIY Junior Member young707's Avatar
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    OK, we are in San Jose, Northern California. So what is the electric vs Gas cost comparison.

    Also, the water heater listed in Home Depot is GE "Ultra Low NOx Gas" 40 gallon, GP40T06AVR/187-918, 32 KBUT per hr, 32.3 Recovery in G.P.H. 90F Rise, 73 First hr. Del. G.P.H., Energy factor 0.59. $497.

    Lowes is Whirlpoot, 40 gallon, 6 yrs, $418, #333578, 125lb, 62"x18" dia,

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by young707 View Post
    OK, we are in San Jose, Northern California. So what is the electric vs Gas cost comparison.

    Also, the water heater listed in Home Depot is GE "Ultra Low NOx Gas" 40 gallon, GP40T06AVR/187-918, 32 KBUT per hr, 32.3 Recovery in G.P.H. 90F Rise, 73 First hr. Del. G.P.H., Energy factor 0.59. $497.

    Lowes is Whirlpoot, 40 gallon, 6 yrs, $418, #333578, 125lb, 62"x18" dia,
    YOU have your utility bills, and thus know what your local utility rates are! We can only tell you what OUR rates are. Most places, NG WH is cheaper to run than an electric one...run the numbers using YOUR rates, and you'll know!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    General Engineering Contractor ballvalve's Avatar
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    One thing to remember is that PROPANE is a rip off and then the electric looks great.

    I hate to see gas in any house from a safety standpoint. Every year many end up looking like the twin towers.

    I do not believe there are ANY pilots in California. Hot surface igniters, mainly.

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    Moderator & Master Plumber hj's Avatar
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    You do NOT connect an electric water heater with a "5 foot extension cord receptacle, and breaker", not do you use a "plug in timer" to control the heater. The only time a timer saves electricity is if you use ALL the water in the tank, and can wait until the timer turns it back on to reheat the water. In the meantime, you will only have "cold" water. A 40 gallon elecltric heater is almost a dinosaur these days because 50 gallon heaters either cost about the same, or in some cases less, than a 40 gallon one.
    Licensed residential and commercial plumber

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