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Hybrid water heaters?

Post in 'The Green Room' started by latichever, Nov 4, 2011.

  1. latichever

    latichever Member

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    Any experiences or recommendations with hybrid water heaters?

    Since I got my pellet stove, I've cut way down on fuel oil for heating. But I just got a fuel oil delivery for almost $600. Last topped off in June, so most of that must be going for hot water that is headed in our ancient tankless system.

    While looking into solar, I came across mention of hybrid heaters at Consumer Reports:

    "As recently as last year, replacing a broken water heater meant paying a few hundred dollars for a relatively inefficient storage-tank unit or spending thousands to eke out energy savings with a solar or tankless system. But smarter new heaters are changing that.

    "Three we tested saved enough energy to pay for their roughly $2,000 cost in about five to seven years rather than decades. Known as hybrids, they have a conventional electric storage heater paired with a heat pump that extracts heat from the air and uses it to help heat the water. Models from GE, Rheem, and A.O. Smith used almost 60 percent less energy than standard electric heaters, which account for roughly half of all water heaters sold. That's a $325 savings per year, based on national average costs for electricity."

    To that they add savings from tax incentives, although a federal tax credit ran out last year.

    Thoughts? Thanks.

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  2. woodgeek

    woodgeek Minister of Fire

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    Lots of threads here is you search on the product names. If you have a space to put them, they seem like a good deal.
  3. jimbom

    jimbom Combustion Analyzer

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    They are compared to standard electric water heaters in the consumers report. Perhaps should be compared to all options for hot water available to you using your energy rates at your house.

    I looked at one of these a year or two ago. Couldn't get the energy consumption data when the heater was in heat pump mode. Since each home will use hot water in a different manner, I wanted to see how it would work for my climate/situation. So I passed on the purchase due to lack of that information. Stuff like this that I buy has to pay back or I don't get involved.

    The payback seems to be sort of like EPA auto mileage. If you drive like the EPA test, you will get the EPA mileage. Otherwise, your mileage depends on how you use the car.
  4. maple1

    maple1 Minister of Fire

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    I've got my eyes on Geyser, and fully plan to get one & incorporate it into my system overhaul next year.

    From my checking, they put solar ROI to shame.
  5. woodgeek

    woodgeek Minister of Fire

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    I guess you are talking about 'Hybrid Mode' where it uses an electric coil if it thunks its going to run out of water....you don't want to run to close to the first hour rating, or eff will suffer. Posts by owners on this board, however, suggest that 'straight HP' mode works fine for them--they switch to hybrid if they have a houseful of guests, and then switch it back afterwards....

    For the geospring, the rated 'Efficiency factor" is EF=2.4 in HP mode, compared to EF=0.85 for a conventional electric tank. IOW, its operation cost in HP mode is ~1/3rd that of an electric tank (0.85/2.4). For most folks that's an operating cost of a 250-400$ a year. Gas might be competitive, but everything else is probably more expensive. If the OP is filling his tank 2x a year for DHW, and doesn't have a gas option, then the HP a great solution, that will save him nearly $1000/yr, for a decent payback time.

    He should def crunch the numbers, however. In my case, my space is semi-conditioned, and probably too cold for HP mode 3 mos of the year. This will hurt my payback a little (I too have a tankless coil), but I will pull the trigger when work slows down a little...
  6. jimbom

    jimbom Combustion Analyzer

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    During the heat pump only mode, the energy consumption in kW and/or the output in BTU/h would be very interesting to me. I have possible application for my radiant flooring. Performance information would tell me the number of days in the spring and fall this might work. For instance on a DD=20 day with no sun, I can maintain indoor comfort with about 5,000 BTU/h. If this unit could handle that, I could figure how many months in the year this unit could be used for our hot water and space heat.
  7. woodgeek

    woodgeek Minister of Fire

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    Sooo, during the shoulder season you would feed the coil outside air and dump DHW into the radiant. The input/output would depend on the temp of the air you are delivering to the coil....
  8. DBoon

    DBoon Minister of Fire

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    I have a geyser heat pump water heater connected to my Marathon hot water heater. I have day/night metering, and I used to run my electric resistance water heater at night, so I could estimate my consumption pretty accurately at 200 kWh/month. With the Geyser in the summer, I would run about 90 kWh/month. In May (when I installed it, and when the basement was about 50 degrees F), it used about 105 kWh/month. So it cut my electricity use for hot water heating by about half.

    I was also able to avoid running a dehumidifier most of the summer because it dehumidified the air while heating the water. That saved me about another 100 kWh/month as well.

    I liked that the Geyser was an add on to my existing hot water heater. It was about $1000 vs. $2500 for an integrated system. The extra $1500 wasn't worth it for me for an integrated system, though these will be more efficient since there aren't the exposed hoses as with the Geyser. There are hoses to the HW heater to the Geyser and from the Geyser back to the HW heater. These must be insulated really well or the efficiency will go way down. I used rubber insulated tubing - you have to cover every exposed surface.

    I've never used an electric resistance backup. The Geyser handles all my needs.
  9. Jaugust124

    Jaugust124 Feeling the Heat

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    Been pondering this same question as OP ever since I read that Consumer Reports article some time age.

    Right now, I believe in NY that the total rebate is $700, which makes it more appealing. My problem is, I can't quite figure out the pay back. We currently heat our hot water with an oil fired boiler and I'm not sure how to compare it to electric. Obviously our electric bill will go up, but not sure by how much. Around here we pay about .16 cents per kwh. Its just the wife and I and we do not use the dishwasher. I went on the A.O. Smith website and at .16 it said it would cost us just over $200 per year for dhw. Don't know how accurate that is.

    We just got an oil delivery and the last one was in June. Based on that, we use 20 gallons of oil for dhw, probably a bit more in the colder months since the shower is probably hotter and maybe a bit longer shower. The price was $3.55 / gallon, so at 20 gallons / month that equates to $71 / month or $852 annually. If it cost around $200 / year with the new water heater we would save over $600 / year not including the cost of the added electricity. Seems to be worthwhile with a short payback period of about 3-4 years dependent on the variables.

    One other thing, I have heard that the boiler sitting around unused all for 5-6 months can lead to problems.

    If anyone has any thoughts on this whole thing, I would love to hear them.
    Thanks.
  10. woodgeek

    woodgeek Minister of Fire

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    Your numbers look a lot like what I got--but my DHW and oils standby are both higher. As for shutting down for the summer, it might be a problem, but I think a lot of folks do it. IN my case, I will get my boiler torn out as soon as I have a DHW solution....

    On a BTU basis, 15 cent/kWh is the same as ~$4.60/gal oil (assuming 100% for the elec, 80% for the oil). So, with a COP of 3, a BTU on the HP is less than half as expensive as $3/gal oil. BUt the big savings are in reduced standby.
  11. DBoon

    DBoon Minister of Fire

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    I agree with the previous calculation - I calc'd it a while ago with a night rate of 0.10/kWh and my oil break even rate was $2.75/gal or so. If you don't use a lot of hot water, the HPWH will be more efficient since you won't have the low efficiency cycling of the oil burner.
  12. Jaugust124

    Jaugust124 Feeling the Heat

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    Thanks for the replies. I am also looking into the whole solar thing. From what I understand, the solar hot water can also be used in baseboards or as radiant heat in flooring. Hmmm. Seems a bit more interesting and may make the payback period a bit shorter. Probably just all really a dream at this point, but might consider something in the not too distant future. More research needs to be done on my part.
  13. jebatty

    jebatty Minister of Fire

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    A piece that usually is little discussed when energy efficiency is the topic is the value of low-tech conservation and high payback, from things as simple as low-flow faucets and showers, to additional insulation, to heat traps, to plain reduced usage. I love high tech, especially when it is economical. The best solution for our DHW situation, all electric, was no more than: 1) raising the hot water heater off the floor on a 2 x 4 frame; 2) insulating under the hot water heater and adding 6" of fiberglass insulation around the sides and top; 3) adding effective heat traps on the hot and cold water lines to prevent thermal siphoning; and 4) insulating all the hot water pipes that we could get to. Total cost of all of this was about $50-75, and the reduction in electric usage was 50%. Of course, we also have all the low-flow devices as well, we don't stand in the shower for lengthy periods, and we are moderate in our use of bath water and other uses of hot water.

    Purchasing a HP, hybrid, or any new hot water heater for energy savings just doesn't add up when nearly the same savings can be had for $50. But, if a new hot water heater is in the picture anyway, then purchasing one without also implementing other conservation is akin to throwing the baby out with the bathwater.

    I definitely will consider a heat pump hot water heater when it is time to replace our electric resistance hot water heater. Since we already have implemented conservation measures, the significant area of savings with the hp hot water heater may be summer-time dehumidification in our basement, a big expense which I do not otherwise know how to reduce, if sufficient dehumidification can be provided. Right now the energy star rated dehumifier runs nearly constantly most of the summer and it is on the "less dry" setting, and at this time I doubt a hp hot water heater can do the job.
  14. woodgeek

    woodgeek Minister of Fire

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    Research (and quotes) are always good. Be aware that the solar output will be highly seasonal--typically there is will be excess during the summer months (that many systems have ways of automatically dispersing to avoid damage), and during the winter it may run short requiring a good amount of backup heat. In the northeast, this is more a function of lots of winter clouds and clear summer days, rather than any engineering of the system. If we were out west, it would be another story.

    My point is that in your climate its unlikely that a Solar DHW system will have excess heat in the winter to provide for radiant heating. It will likely have excess in the summer that could be used to heat a jacuzzi.
  15. DBoon

    DBoon Minister of Fire

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    jebatty has very good advice on conservation - that is always the cheapest way to go. First, cut hot water usage and insulate your tank really well. Then make another investment. You may find that conservation and insulation does all that you need.

    My hpwh add-on mostly kept my basement dehumidified, but I don't have a wet basement. I used to run a dehumidifier about 7 hours a day in the summer, and the hpwh runs a little less than that now per day. If you had a wet basement, you would probably still need a dehumidifier, but it would run less.

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