Electric water heater: Any insight/experience?

skoobus

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Joined
Sep 16, 2021
Messages
29
Hey all, just wondering if anyone can share any insight or experience on using an electric water heater.

The one I'm looking at is a small 2.5 gallon bosch mini says its (max?) wattage is 1440. Probably just enough for dishes and whatnot.


I'm just kind of hoping somebody can share about how much power in a day one can expect to be using in real life experience, obviously everybody's situation is different.

I don't think it runs at 1440 watts all the time, but considering I only have a 3000 watt inverter it sounds a little sketchy to me but maybe I could make it work with careful use. Hopefully you guys are much smarter than me and you can set me on the right path.

Pretty scared about propane, we're going to be in a vehicle and with the bad reviews for like every single rv-style water heater both propane and electric.. I'm hoping to go electric because while it can flood I don't think it can really go boom.

Thanks in advance y'all.
 

Groscout

Knowledge Versus Understanding
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May 2, 2021
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Good morning @skoobus, My personal experience is that what you’re talking about works within reason even though the general consensus is no.

I have a 110v/propane 6 gallon water heater with a 1500 watt element(it pulls between 1400-1600w depending on water temperature).

It heats a cold tank with about 10ah @ 48v/ 480-500Wh.

It re heats the tank with about 8ah @ 48v/384wh if I recall correctly (re heat may take less I’m still looking for my records on this). What I mean by re heat is when it cools off by itself without running any water and has to bring the water back up to temperature. I found that it ran like six times per 24 hour period without running any hot water (this test was done in summer time outdoor temperatures, this is relevant because of the nature of vented gas water heaters). Keep in mind that the water heater you listed will cool down slower than what I’m using due to it not having a gas vent constantly cooling the water heater off with outside air.

I was also using a 3000w inverter.

Also keep in mind I’m pulling water from inside storage that stays around room temperature as to reduce the water temperature delta so YMMV. 70-72f to 120f is different than 50f to 120f

You will definitely want to turn it off at night or when not in use while boondocking.

If you’re using electric water heating on solar only, you’re probably going to want to do most of it during the day or during peak sunlight hours.

The propane side of operation of my water heater works great and has never been a problem with automatic ignition (NO pilot light that’s always blowing out!!), it totally takes care of itself. Although I totally understand not wanting propane at all.

Just remember plugging or improperly discharging the temperature and pressure relief valve can create a bomb. Just watch the myth busters episode on exploding water heaters.
 

740GLE

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Apr 30, 2021
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635
Propane on demand? Lots of small portable units, you can mount externally to avoid concerns with saftey.
 

Frick

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Mar 20, 2021
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119
If you mobile, and have propane on board, the rv water heaters are good. Heat fast, reliable, generally problem free. I used to have a suburban 6g propane with electric 120v element. I could run either method to heat, or both for faster recovery.

depending on your set up, you may not be able to run anything heat related off solar. AC, space heater, hot water, stove. They all consume vastly more power than anything else. An induction stove is at least efficient and many run those for light cooking.

also, when Calculating water usage, dishes is something that surprises people at how much they actually use, usually many times more than they guess. With a low flow shower head (critical) two people could have a nice shower without feeling rushed on a 6gal water heater. Dishes though used all of it, and then more later when it recovered.
 

skoobus

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Sep 16, 2021
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29
I guess the consensus is pretty much "it might work *maybe*, but propanes way better" lol

for only about $150 I think I might give it a try for now and continue looking into more about the propane units. Most likely I'll upgrade later on and keep this little guy as a backup. All my other appliances are 12v, so hopefully at least I won't risk overloading my inverter -even if I do drain the battery bank.

Thanks again everyone for being super helpful!
 

Kdkool

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Oct 17, 2021
Messages
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It really depends on your battery bank. I have a 2.5-Gallon water w/ a 1500W heating element in mine. It really depends on how often you're depleting your hot water. The absolute worst case scenario for us is that everyone (4 of us) has to shower on a cold night where we all deplete the hot water for each of our showers while we're boondocking.

My math came out to a little under ~19 mins of water heater run time to heat 10C water to 50C for (40C delta) each person. This would mean I'd need at most ~75 minutes of running the inverter at 1500W to accommodate all the showers.

In all actuality, it's nowhere near that much usage. If we all took showers long enough to deplete the hot water tank every time, we'd be out of water. I timed my water heater to take about 5 mins of heat up time in between each shower with outside temperatures at ~10C. I have a 24V 3000W inverter with 310aH lithium cells. I have plenty in the budget for my use case.

I took out my propane tankless water heater and replaced it with an electric one. We had worlds of problems with the flow rates to trigger the hot water heater. Especially with low flow rates in attempt to save water. It also sucked that inlet water temps was always different throught the seaons on how much we needed to adjust our hot water flow. It helps if your camper has separate hot / cold knobs. Those faucets that combine hot and cold are not a good use case for saving hot water.

Hope that helps.
 
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Short_Shot

Photon Sorcerer
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The electric only folks will use low wattage heaters in addition to the high wattage one, which doesnt save you energy but saves on the draw.

They will then just turn the thing off until just before they need to use it, and use it as a solar dump load and the high wattage unit on shore power (or generator, or right before using it).
 
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dakine

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Sep 21, 2019
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Northern California
I have the Bosch ES4 (a little larger) for a booster hot water heater in my house and connected to a sink. We use it 8-10 times a day for hand washing and quick rinsing off. Similar to what glentaylor said, ours uses about 1.2-1.3kWh per day, and probably spikes up to ~1400W when heating, but it seems to heat quickly due to the size of the tank.
 

efficientPV

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Sep 24, 2019
Messages
482
I've used an ECOsmart6 which is a decent heater insulation wise. I now use a 50L one from China which is enough for our needs which includes a dishwasher. Insulation is terrible and I had to wrap mine. 1500W, but there are versions which can switch to as low as 800W. Make sure because many of the three way switches are dummy.
 

cotswoldstony

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Jul 4, 2020
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Cotswolds South West U K
Here in the UK we have low wattage water heaters 800w fitted in motorhomes and caravans and propex low wattage water heaters 8/10 litres on conversions.
To use these on solar you need the same size wattage solar array minimum and only turn the water heater on when your battery bank is fully charged normally after midday.
The water heater will then be almost running directly from the solar array and the water will remain hot for the afternoon and evening.
I heat the water on 2 caravans this way from one solar generating system/3kw inverter.
 

Henrysangret

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Joined
Dec 5, 2020
Messages
37
Hey all, just wondering if anyone can share any insight or experience on using an electric water heater.

The one I'm looking at is a small 2.5 gallon bosch mini says its (max?) wattage is 1440. Probably just enough for dishes and whatnot.


I'm just kind of hoping somebody can share about how much power in a day one can expect to be using in real life experience, obviously everybody's situation is different.

I don't think it runs at 1440 watts all the time, but considering I only have a 3000 watt inverter it sounds a little sketchy to me but maybe I could make it work with careful use. Hopefully you guys are much smarter than me and you can set me on the right path.

Pretty scared about propane, we're going to be in a vehicle and with the bad reviews for like every single rv-style water heater both propane and electric.. I'm hoping to go electric because while it can flood I don't think it can really go boom.

Thanks in advance y'all.
You do understand that they have been putting propane HW heaters in RV’s for over 50 years so I am sure they have the bugs worked out, AND they use them inside homes as well. Propane is better than electric for batch heating, but I use electric as a propane HW heater water preheater run off my solar excess when batteries are done charging.
 

kuranaga

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Joined
Sep 24, 2021
Messages
164
what I did with me electric water heater:

it has 2 heating elements, both 900W/230V. It can be setup via buttons to use either one or both of them (if water is hot already it will only reheat using one element, but if it is cold it will boost it using two). So now what I did I put both elements in series and setup the heater to use generally only one element. Then connect the two series into the first heater port and I get an electric heater heating with only 450W ;)

yeah if you put that into the formulas two 900W/230V elements in series running at 230V will just give you half of the power of one element.

takes long to heat the 80L tank but it will not kill the batteries. I also added a programmable timer so it only heats during sun time.
 

circus

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Jul 8, 2021
Messages
271
I know my coffee maker works and it could be a water heater. In a pinch, I could pour it's content into a basin with cold water for what ever reason. Not as nice as on tap but, for 20 bucks, worth a try.
 

svsagres

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Nov 14, 2021
Messages
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We have a 5,3 gallon Isotemp hot water heater on our 27’ sailboat. It’s dual heat capable (750W electric heating element plus a heat exchanger for engine coolant). Right now, our engine is raw water cooled, so we’re purely electric. If we repower to a freshwater cooled engine, then we’ll hook that up.

Anyhow, the key thing is that the heater heats the water to about 90C (200F or so) then uses a mixing valve to mix that dangerously hot water with cold water and bring it down to safe levels. This means that 5.3 gallons lasts almost double. Also, the the isotherms are so well insulated that we can easily have hot water for dishes 18 hours after leaving the dock.

We’re in the process of doing an electrical upgrade on the boat, and will probably add a victron 2000W inverter/charger and connect it to the hot water tank through a breaker. There should be enough power of our our alternator to run the tank while we motor in to our anchorage.
 

kuranaga

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Joined
Sep 24, 2021
Messages
164
We have a 5,3 gallon Isotemp hot water heater on our 27’ sailboat. It’s dual heat capable (750W electric heating element plus a heat exchanger for engine coolant). Right now, our engine is raw water cooled, so we’re purely electric. If we repower to a freshwater cooled engine, then we’ll hook that up.

Anyhow, the key thing is that the heater heats the water to about 90C (200F or so) then uses a mixing valve to mix that dangerously hot water with cold water and bring it down to safe levels. This means that 5.3 gallons lasts almost double. Also, the the isotherms are so well insulated that we can easily have hot water for dishes 18 hours after leaving the dock.

We’re in the process of doing an electrical upgrade on the boat, and will probably add a victron 2000W inverter/charger and connect it to the hot water tank through a breaker. There should be enough power of our our alternator to run the tank while we motor in to our anchorage.
you must be very careful about your piping! if the mixing valve malfunctions it will kill your pipes. even cpvc is risky at 90°C. I hope you have copper pipes
 

svsagres

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Joined
Nov 14, 2021
Messages
57
you must be very careful about your piping! if the mixing valve malfunctions it will kill your pipes. even cpvc is risky at 90°C. I hope you have copper pipes
Be design, mix valves will fail safe (ie cold). This is a safety critical system as 90C water would be exceedingly dangerous coming out of a tap or shower head.

That said, all the hose we use for our plumbing system is rated for 90C.
 

Short_Shot

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Jul 13, 2021
Messages
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You do understand that they have been putting propane HW heaters in RV’s for over 50 years so I am sure they have the bugs worked out, AND they use them inside homes as well. Propane is better than electric for batch heating, but I use electric as a propane HW heater water preheater run off my solar excess when batteries are done charging.
Yeabutt.

Propane is annoying to get refills for if you have enough space and money for batteries.

Personally I'd use a diesel heater with heat exchanger that can double as an engine heater. If it were on an rv rather than a trailer anyways.

Might still consider it for a trailer too.
 
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