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Join Date: Feb 2010
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Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/23/2010 4:52 PM

I need a new hot water heater. My old one was a conventional gas, in my basement. I'm considering

-tankless unit,

-"hybrid" from Rheem,

-solar, or

-"Vertex" from AO Smith.

I'll probably install it in the basement where the old one was. Too many choices.

I'm so confused. I'm not a tech guy - I need advice! Thanks!

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#1

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/23/2010 5:15 PM

It all comes down to user preference as many pieces of equipment do. I will tell you I am absolutely 100% satisfied with my Rinnai tankless propane heater (different models with different jets can use natural gas of course). It has to heat the water on demand so you won't get hot water as fast, but we don't notice a large enough time and flow difference. I grew up in the SW and my dad purchased a solar hot water heater in 1976. I remember in the early 80s when I was in engineering college discussing his notes he kept (those engineer dads) for a number of years after his purchase to document the cost benefit, electrical use now and then, and how well the system worked (and paid for itself after 7 years). If it was me, I'd check into solar ones too.

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#2

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/23/2010 7:11 PM

Come on you coward. You don't need to be a tech guy. Gather some spec's and do some evaluation. It might be fun.

I don't know anything about them, either.

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#3

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/23/2010 7:25 PM

It comes down to usage.

How many people are living in the house? Don't forget guests, Klingon's and sundry associates who regularly use the facilities....

Are any of these people teenagers with long hair? It doesn't matter if male or female.

Instantaneous heaters are good in homes with minimal "traffic" but if the water usage is high then so will the operating costs.

In an "average" household with teenagers the larger the storage tank the better be it conventional or solar system.

The thing with the solar hot water system is that if you have a couple of days with cool temperatures and no sun you will need to run the booster. Even in Oz, during winter the booster in my house switched on more than not. But its overall power usage was significantly less than a conventional electric hot water heater.

Note: An electric hot water system only draws power when its heating the water up to temperature. A larger tank may take longer to heat initially but will maintain that temperature for longer than a smaller tank. Not exposing the tank to the elements also helps.

Similar for a gas fired one, you would need to compare price of gas to electricity to see which one would work better for you.

My house up until recently had 2 adults and 2 teenage girls as the main complement, added to that on the weekends, was a cast of about 8 sundry associates and Klingon's. This used to test the efficacy of the solar hot water service with the 500litre storage tank. Being an early riser I never had a problem, some of the klingon's on the other hand, well that was their problem...

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#4

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/23/2010 11:17 PM

Instantaneous electric units may require a large amperage power circuit. We have had some at work that rarely worked correctly. Not sure why. Because of that limited experience I cannot recommend instant electric.

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#5

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 12:39 AM

You can probably rule out putting a solar hot water heater in the basement :D

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#7
In reply to #5

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 5:28 AM

Actually my solar hot water heater (tank) is in the basement.

For some strange reason the installer insisted on placing the panels on the roof though.

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#6

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 1:08 AM

I'm with Matt Skywalker: "I am absolutely 100% satisfied with my Rinnai tankless propane heater."

Bang for buck, nothing beats them.

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#8

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 5:34 AM

One comparison chart I came across for costs over 13 years - assumed energy costs are at the bottom.

From this the heat pump type of hot water heater has the best costs but that depends on the escalation of power costs.

Hot water heater operating costcompared to
typeefficiencyinst costann energy costlifecost over 13 yearscost per yearkWh/yearheat pumpkWh/month
conv gas storage0,6$850$35013$5.394$415131%
hi eff gas storage0,65$1.025$32313$5.220$402127%
condensing gas storage0,86$2.000$24413$5.170$398125%
conv oil fired storage0,55$1.400$6548$11.299$869274%
min eff elec storage0,9$750$46313$6.769$5214.874164%
hi eff elec storage0,95$820$43913$6.528$5024.621158%440
demand gas no storage0,8$1.600$26213$5.008$3852.758121%
elec heat pump2,2$1.660$19013$4.125$3172.000100%278
solar w/elec backup1,2$4.800$17513$7.072$5441.842171%477
eleckWh$0,09540%
ngtherm$14,0025%
oil$2,401155$109,75
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#9

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 7:39 AM

I purchased a Rheem Marathon electric water heater. It is plastic, and comes with a lifetime guarantee. I am going to reinstall my roof mounted solar system to it this year. The Marathon was the highest efficiency WH I could find 4 years ago. My WH is mounted outside, and I was replacing them every 3-4 years.

As a side note, solar and gas powered WHs do not mix well as the exhaust venting allows too much heat loss when now warming water.

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#10

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 9:42 AM

As most of the respondents, I am speaking from personal experience. I have electric instantaneous hot water heaters and they are slow. The gas models are much faster. However that having been said, I am adding a solar thermal panel outside and hooking that up to the instant hot water heater. I am also adding in-ground hot water storage, and a lot of it. The results should be that my electric bill will come down dramatically.

The theory behind my decision is that if I can keep my water going into the instant water heater warmer than the lowest setting, It will not kick in at all. I have two of the largest units that Sets manufactured 6 years ago and even together I cannot get enough heat to fill my large tub without filling it very slowly. I am sold on solar thermal and in-ground storage.

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#11

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 9:53 AM

I have three Schuco panels and a 325 liter tank with electrical backup.

The power was on for 16 days in February and will be needed sometime in November - probably late in the month.

The system pump uses an average of 780 watts per day based on meter readings over a period of time.

We don't have access to natural gas where we are and LPG is priced as road fuel so not attractive.

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#12

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 5:18 PM

When I lived in Florida I had a new heat pump HVAC system installed in my house. This system included a Heat Recovery Unit, which took the 'free' waste heat from the AC and sent it to the hot water tank. For about 9 months of the year I had 'free' hot water -- and lots of it.

During the 3 cool months when I was running the heat pump in heating mode, the same system 'stole' some of the heat and sent it to the hot water tank. This hot water wasn't exactly 'free' but it was cheaper than the electric resistance heat used when normally running the hot water. The $$ saved in not having (or seldom having) to heat water practically paid for the new HVAC system in 5 years.

Best money I ever spent. Here's a link to some info, though this was not the system I had.

http://www.trevormartin.com/hru.asp

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#15
In reply to #12

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/25/2010 12:37 AM

Free hot water - partially. When the AC unit is running and I suppose in Florida that is much of the time.

I didn't turn on the AC this year and had the heat pump on for three months so not such an interesting deal.

From the Trevor Martin document in the link above: Generally speaking, you need to get above 14 SEER before you even have to worry about the hot refrigerant temperature being too low to enable the heat recovery to work.

So if a new heat pump is one of the energy efficient models the desuperheater for heating DHW is of no use.

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#13

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 7:27 PM

When it comes to water heaters, No Tanks!

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#14

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/24/2010 11:20 PM

I'm with Tommm. Except preheat is an excellent idea. Use black pipe or whatever and let the sun do the preheating.

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#16

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

09/25/2010 12:37 AM

Using tankless water heater may be ok for saving, but just make sure your water is not hard water or it will have lowered efficiency after sediments accumulate in it. Or worse, you will need new one after a few years.

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#17

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

10/02/2010 8:14 AM

Tankless water heaters have much to be said in favor of them.

However, ask the question to someone who has installed one in a natural gas equipped house: In your experience was the natural gas piping sufficiently large or did the demands of the instantaneous water heater cause the piping size to have to be increased? Is the burner manifold pressure in an instantaneous water heater 3.5" w.c. like conventional gas appliances?

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#18

Re: Which New Hot Water Heater Should I Get? Tankless? Hybrid?

10/05/2010 4:10 PM

My apartment building has a common hot water tank, and sometime back in the day I worked out how the owner could benefit from purchasing solar collectors and tankless gas heaters. I could not see any downside, even though the gas water heater tanks are still in good shape. (The pay off for even a single collector was rapid, since I assumed that the maintenance crew would do the install without the vendor's labor markup, and they would use the existing tanks for thermal storage - a big savings.)

So, if you are willing to invest similar "sweat equity" and you can handle the plumbing if not the "tech", I hope you jump in with both feet. If your tank is not leaking, I suggest you replace the "sacrificial anode" and use it as your first solar thermal storage tank!

If you are going electric then a "hybrid" heat pump is better than tankless; if you are going with gas or propane then tankless is better than tanks.

The "hybrid" electric heat pump may be less expensive than gas (do-the-numbers); but also consider whether the electricity is from coal or a more benign fossil source. Here in Pennsylvania, I personally prefer to use a natural gas source as a backup to solar because electric is coal-based.

p.s. (off topic - but important) You need to feed your "inner tech-guy": Be sure to learn how proportioning valves work; they are an important feature when combining solar and conventional heating, and many installers get it wrong or omit them entirely. For example, I wouldn't feed a high-efficiency tankless gas heater from a preheated solar storage tank. That would sabotage the efficiency. Instead, install a proportioning valve's cold inlet directly at the solar storage outlet and run the hot inlet to the tankless gas heater. (I know, I know, someones hackles are rising!) When the stored solar heated water gets below 130F, the tankless system will take over fully, using icy cold tap water to pry every possible BTU from the flue gas. Run a line from the same solar storage outlet to a second proportioning valve's hot inlet to provide tepid water to all the cold water faucets instead of icy cold water. This will squeeze every last BTU possible from the solar collector, saving on fossil fuel and stretching the capacity of the backup system.

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