Gas to Electric conversion because of remodeling limitations?

Discussion in 'Water Heater Forum, Tanks' started by ktc, Oct 13, 2012.

  1. ktc

    ktc New Member

    Messages:
    3
    Location:
    Seattle, WA
    Hi there,

    I'm a first-time homeowner and also decided to tackle on a remodel project, and hit a dilemma that I was hoping to run by all you experts :confused:

    We have a master bedroom in the basement and an unfinished adjacent room where there is currently a 3-year old Rheem Fury 50-gal, and we're converting this space into a master bath. Unfortunately, our plumbing inspector is requiring all combustion air to be supplied by the outside, and based on the nearest wall being >30 feet away, my choices are limited to getting a power direct vent system or a direct vent tankless. So that is likely going to be $1200-1500 hardware cost, plus perhaps another $500+ labor for my plumber to get the ducting done. Then I'm assuming potentially the blower may be loud (the WH closet will be near the door to the bedroom), and there may be blower repair costs, and annual maintenance/cleaning costs for a tankless.

    Would going to a 50-gal GE electric WH be logical in this case? Based on prior similar threads on this forum, right now my electricity is $0.0987/kwh. Per GE's approximation of 4622kwh/year, that's $456. Based on my last gas bill, it's approx $1.58/therm, so in comparison:
    A) Rheem tankless 95DVLN burning 159.3 therms/year will be $252/year. Plus ~100/year for cleaning, it ends up being a $104/yr savings over a GE electric.
    B) Rheem PDV50 tank burning 223.3 terms/year will be $353/year. So it ends up as a $103/yr savings over a GE electric, as long as the blower fan doesn't require any repairs.

    Both of these units will probably cost an additional $1,500-2k over the GE electric for the complete install, and based on the scenarios above it would take 10+ years for the cross-over price advantage, unless the cost of Seattle city electricity increases substantially. Plus, the electric tank storage has the advantage of a completely silent, zero risk of gas emissions, and 1 less hole in the side of my house ;)

    Can you guys provide your opinion on this scenario? Perhaps my math is wrong? I would need to make a decision soon for our remodeling to move forward...

    Many thanks,
    ktc
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    Before considering a tankless, what is your expected max draw and what is the coldest incoming winter water temperature? The max gallons listed in the big print on a tankless assumes some fairly warm incoming water compared to some places in the US. Mine can be barely above freezing during a cold snap in the winter, and to get any decent volume of hot water would need a huge tankless. You may need to upgrade your supply and almost certainly the line to that WH to go tankless to be able to supply it properly. A too small gas supply line will compromise the operation substantially.

    If you're planning a large soaking tub or a multiple jet shower arrangement, 50-gallon electric (and probably gas, too) is too small.

    While it's nice to have the WH close to the bath for speed of hot, with the addition of a recirculation system, it can be relocated to where it may be more convenient. Why take up space in your new bath for the WH?

    But, the easiest conversion would be to just go electric. Keep in mind that the recovery rate is lots slower than your current gas unit, and that may affect your sizing decision - a direct swap in size compared to the gas unit may not suffice.

    Forget about an electric tankless.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Electric tankless are very wimpy, and the manufacturers suggest never installing one above the Mason/Dixon line. As far as an electric tank, your rates are below the cost in most areas, so you just need to consider capacity, due to very slow recovery rate compared to gas. You might want an 80 gallon. You do also have to condsider the cost of the install. Will your house service support a new 240 volt/30 amp circuit/??
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    Does your indicated electric rate include all of the line charges, distribution charges, and taxes? I wish my rates were that low, they're at least double if that's the delivered rate.
  5. ktc

    ktc New Member

    Messages:
    3
    Location:
    Seattle, WA
    Thanks Jim and Jimbo.

    Seattle electric is very reasonable: http://www.seattle.gov/light/accounts/rates/NUand25CitiesRateTable.pdf
    It is surprising, but apparently my $0.0987/kwh is the current highest delivered total rate, all-inclusive. The first 10kwh/day is even less. As such, I think using an electric here in Seattle is quite reasonable, albeit still more expensive than gas.

    Our cold water supply temperature is approx 48F according to http://www.pacinst.org/resources/WECalc/WECalc_data_and_assumptions.pdf . I don't know too many people in Seattle who use an electric water heater but would imagine 48F is not too far from the norm.

    I'll see what my plumber comes up with tomorrow... we're also getting the electrical guys to make sure we can support a 30A line for the 4500watt electric tank heater... it probably shouldn't be an issue and we already have the ceiling opened up for the rest of the remodel. We do have a 3/4" gas line right there in case we want to go Tankless, but again I think the venting is really where it gets expensive for our unique situation. We're also talking to them about an external tankless and see if it would be more cost-effective to just run a gas and water line outside instead... the other thing I didn't mention in the original post is that currently it's just 2 people in this household, and we might move out of the house in 6-7 years. Perhaps if by then, tankless / other technologies would be even more advance, and we can upgrade then?

    Any suggestions for reliable and cost-effective electric tanks? There's a big flurry of anti-Whirlpool posts from a few years back but perhaps the latest electric ones are ok?

    Thanks,
    ktc
  6. Dana

    Dana In the trades

    Messages:
    2,922
    Location:
    01609
    Look at a winter gas bill for a more representative $/therm average. $1.58 seems a bit on the high side, and may reflect a high fraction of the summertime bill being the monthly charge just for being hooked up to the gas-grid.

    Even an a 0.55EF gas fired tank you get ~55,000BTU/therm applied to the hot water. In a 0.90EF electric tank you get (0.9 x 3412= ) 3071 BTU/kwh. So the rough equivalency is it takes 17.9 kwh to get the same amount of hot water as you get out of a therm. So even at 9 cents/kwh that's like heating the water with $1.61/therm gas- roughly equal. At 10 cents/kwh it's measurably more. But if you swap in a power-vented condensing take like a Vertex or similar you'd be running 0.85 EF or better and cost dramatically less. Unless you have a monster-tub to fill there's no real advantage to going with a gas-fired tankless, but a condensing gas tank offers a HUGE improvement in recovery time and first-hour gallons over any electric tank, and don't have as many maintenance issues as a tankless. (Blowers are pretty robust- it's mostly the other stuff on a tankless that adds to maintenance issues, and the controls of a condensing tank are dead-simple compared to a modulating condensing burner like a condensing tankless.)
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    In ten years you will probably have to replace the tank type heater, but from your parameters, I think the electric would be the way to go. You should not even consider a tankless electric, although that did not seem to be one of your options.
  8. ktc

    ktc New Member

    Messages:
    3
    Location:
    Seattle, WA
    Thanks for all the feedback.

    I can't find any threads on specific electric water heaters that are recommended. Are there any specific ones you guys have put in that you would recommend? Is a 50-gal appropriate for a family of 2 or 3?

    Appreciate your thoughts,
    ktc
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