tankless electric water heaters, any good?

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electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
Occupation
Electrician
I have always told people to stay away from these. I admit my experience with them is somewhat dated and of a relatively low sample size, but I have found them to be finicky with holding a steady temperature, particularly as flow rate changes. sometimes they dont even kick on if the flow rate is too low. I have a family member who is considering one. In this case it would draw about 120 amps and would be mounted very close to the electrical panel. I havent installed the service yet, but this thing would not change how I would do the service, other than possibly maybe running 250 instead of 4/0 from the meter, depending on the distance and what the numbers look like. Anyway, so just from a performance standpoint, Are these things any good now? Any direct experience? Come on I know there is someone on here who has 9 teenage daughters who all take showers at the same time :ROFLMAO:
 
The first one I installed at my grandmother's house 20 years ago kind of sucked with low flow. It finally went out about a year ago. I have one at my house, my sister's house and a close friends house. They have all been really really good. Oldest on those is about 6 years. They are newer with variable fire rates. However they are all LNG and not electric. At my house I have what is called a NaviCirc under the sink and it uses my cold water pipe as a return and maintains that water to 95* and will get hot (120*) in 20 seconds. No more waiting for hot water.
 
SSDriver said:
The first one I installed at my grandmother's house 20 years ago kind of sucked with low flow. It finally went out about a year ago. I have one at my house, my sister's house and a close friends house. They have all been really really good. Oldest on those is about 6 years. They are newer with variable fire rates. However they are all LNG and not electric. At my house I have what is called a NaviCirc under the sink and it uses my cold water pipe as a return and maintains that water to 95* and will get hot (120*) in 20 seconds. No more waiting for hot water.
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He specifically asked about electric, not gas.
 
I've installed them in shops with a shower that worked but every home that used them that I wired ended up changing to a couple standard heater with recirc pumps. At higher usage the tank type will be more efficient than lower usage. 1 shower a day makes the tankless way more efficient than a 50 gallon. The 9 teenager example would be hours of showers in the house with multiple bathrooms. Honestly I think the solar heat exchanger with booster water heater or a heat pump tank style are the best options out there now but the solar system is expensive and use propylene glycol that requires more plumbing and retrofitting but if it's new construction I'd push for that now vs later if ever the costs were high enough that I'd care about the 4000kwh a year that a tank style uses.
 
I dont care about efficiency. Electric tanks are pretty efficient and besides we need heat 2/3 of the year here anyway so there is hardly any net loss. Heat pump or solar hot water isnt worth it in this case as Ill be putting in a PV system at a family rate so electricity will be covered. installation is no biggie cuz its right next to the panel. I just want to know if they perform satisfactorily. Im just worried abour lack of steady temperature. This will be a well so pressure will vary.
 
letgomywago said:
Go standard tank then.
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I have an idea I might try at my house for The Best of both worlds. I currently have a 40 gallon tank which is fine most of the time. It is perfect 95% of the time, but I have an outdoor shower that I use even in the winter and that takes a lot of hot water and probably would start to cool off if there were two showers in a row. I thought why not get a small tankless water heater that would go before the tank heater to feed it with warm or hot water. I wouldn't need truly endless hot water so it wouldn't need to be sized very big, just so it's not feeding cold well water into the tank and cooling it down as quick. But then I've got the tank so temperature will be consistent and steady.
 
electrofelon said:
I have an idea I might try at my house for The Best of both worlds. I currently have a 40 gallon tank which is fine most of the time. It is perfect 95% of the time, but I have an outdoor shower that I use even in the winter and that takes a lot of hot water and probably would start to cool off if there were two showers in a row. I thought why not get a small tankless water heater that would go before the tank heater to feed it with warm or hot water. I wouldn't need truly endless hot water so it wouldn't need to be sized very big, just so it's not feeding cold well water into the tank and cooling it down as quick. But then I've got the tank so temperature will be consistent and steady.
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That's probably work and if it didn't help atleast it would hurt as bad as a straight insta hot system. I've just seen so many issues when they don't get perfect flow rate and it makes them just shut off the elements.
 
letgomywago said:
That's probably work and if it didn't help atleast it would hurt as bad as a straight insta hot system. I've just seen so many issues when they don't get perfect flow rate and it makes them just shut off the elements.
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Yeah looks like you can get a 240-40 AMP one which will do a couple gallons a minute at a 35° rise for only $250. I'm sure that would greatly extend the run time of a 40 gallon tank. Another thing you could do is rewire the tank and run another circuit to it so both elements run at once.
 
electrofelon said:
Yeah looks like you can get a 240-40 AMP one which will do a couple gallons a minute at a 35° rise for only $250. I'm sure that would greatly extend the run time of a 40 gallon tank. Another thing you could do is rewire the tank and run another circuit to it so both elements run at once.
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I solved the runtime problem of my shower to indefinite by cranking the thermostat up a few degrees on the hot water heater I already have. I don't know how long the hot water will last but I've taken some pretty long showers
 
@electrofelon : Do you have a plumber that you could have a power lunch over and talk this situation out?

I have a Timer on my electric water heat so I tend to use it when I know the water is hot! I have considered a
water circulation system, but the farest point is across the house and on the second floor. and not really conducive since
the water heater is in the basement.(again on the opposite side)
My understanding is that one is to apply the circulation piping to the farthest point in the system, and that's where
the temperature sensor/check valve goes, is but I've been mistaken before.
 
@electrofelon What are you hoping to solve by going tankless?

You mention that efficiency isn't a factor since tank losses heat spaces that need it.

You mention particular concerns about temperature stability and low flow cutoff.

Are there space constraints, or a need for extended run time?

Jon
 
electrofelon said:
I dont care about efficiency. Electric tanks are pretty efficient and besides we need heat 2/3 of the year here anyway so there is hardly any net loss. Heat pump or solar hot water isnt worth it in this case as Ill be putting in a PV system at a family rate so electricity will be covered. installation is no biggie cuz its right next to the panel. I just want to know if they perform satisfactorily. Im just worried abour lack of steady temperature. This will be a well so pressure will vary.
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That is one reason I don't think the electric tankless is worth installing in northern areas. The tank will lose heat so that is an inefficiency, if the tank is in the conditioned space that heat loss is more load for when you are cooling but is less load when you are heating.

Incoming water temp is also a consideration. colder the incoming water the higher capacity unit you need at a particular flow rate - the larger the service may need to be to handle this as well. On a new system the larger service cost maybe still offsets cost of needing to install gas service if you have no other need for gas. Existing installation that you are converting that may not be the case though, Chances are you only need to add regulators and run the main lines at higher pressure if gas is already existing vs installing an entire new system.

A "pre-heat" tank is a good idea regardless of what kind of heater you are using. Even just an unheated storage tank can bring incoming water temp up before it hits the actual heating unit, of course this essentially increases load on your heating system as it is absorbing heat from the ambient around it, but is taking heat away from the cooling system when it is in use. But if you have 55 degree incoming water and let it stand in a tank long enough to warm it up 10-15 degrees that's less heat the element needs to put into that water "on demand"
 
electrofelon said:
Yeah looks like you can get a 240-40 AMP one which will do a couple gallons a minute at a 35° rise for only $250. I'm sure that would greatly extend the run time of a 40 gallon tank. Another thing you could do is rewire the tank and run another circuit to it so both elements run at once.
Click to expand...
If you're doing solar anyway then using this as a preheater sounds like a fair idea. In general, if your electricity comes from the POCO, gas is a more efficient way to go. While electric resistive heat is close to 100% efficient for water heating, that electricity threw away about 60% of the heating value of the coal or natural gas that was used to create it, and 60% of the electricity in the US was generated by fossil fuels.
 
cadpoint said:
I have a Timer on my electric water heat so I tend to use it when I know the water is hot! I have considered a
water circulation system, but the farest point is across the house and on the second floor. and not really conducive since
the water heater is in the basement.(again on the opposite side)
My understanding is that one is to apply the circulation piping to the farthest point in the system, and that's where
the temperature sensor/check valve goes, is but I've been mistaken before.
Click to expand...
What about the type of pump that goes under a sink and pushes the water from the hot supply into the cold?
 
gadfly56 said:
If you're doing solar anyway then using this as a preheater sounds like a fair idea. In general, if your electricity comes from the POCO, gas is a more efficient way to go. While electric resistive heat is close to 100% efficient for water heating, that electricity threw away about 60% of the heating value of the coal or natural gas that was used to create it, and 60% of the electricity in the US was generated by fossil fuels.
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Yeah i believe there will not be any gas onsite.
 
LarryFine said:
What about the type of pump that goes under a sink and pushes the water from the hot supply into the cold?
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Circulation loops I'm familiar with do a feed and return to the hot water tank to reduce the lag for hot water at the sink or shower or whatever. I can't see you feeding back into the general cold water supply.
 
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