[amaxonor]

Hi everyone,
Shortly I'm going to be building my own cabin out in the middle of no where for some off the grid living. At the moment I've got a 300W solar panel kit, which I'm assuming will be enough, but I can always add to it need be. I'm also going to be purchasing around (6) 35aH batteries for a total of 210aH. Again I will add more if need be. I'm trying to figure out a solution to hot water. I will be drilling a well, so that'll be my supply, but I'm wondering if I can go with a tankless heater. The smallest one I've found seems to be a 3kW model. That being said, do I simply have to purchase a 3kw inverter and I'll be all set? I was thinking about buying two inverters, one for the lights, fridge, etc and one strictly for the water heater. I'm thinking that the heater will only be on for maybe a total of 20 mins per day (showers and hot sink water) so if thats the case, do I simply have to buy an inverter with a wattage rated for that of the heater? Or is there more to it than that. Thanks for all your help!

 

[Stick]

Black barrel on roof in sunshine.

 

[amaxonor]

And that'll still work even in the dead of winter in Pennsylvania?

 

[Stick]

Naw, probably as well as it doesn't work here in winter, either. I have three, one hundred watt solar panels, too, but only three marine batteries. When fully charged, I can get a few minutes of TV out of them. Mostly just runs lights, radio, phone, laptop, and amp for my harmonica. I just don't know about the feasibility of generating solar electricity for heating water...seems like you would lose energy somewhere along the line there, between solar panel, cable, controller, battery, inverter, heating element, when the sun is right there. There are ways to accomplish your goal...others more knowledgable than me will be along, I'm sure. In summer, the sun gives me all the hot water I want, but since I haul my water 12-50 miles, that ain't much. A black five gallon bucket works fine. This time of year the black bucket of water in the sun just keeps it from freezing so I don't have to leave it on the stove so long to heat. Half a bucket hot water, half a bucket cold, stand in a tub and shower with a canteen cup. Do your dishes with the leftovers (after the Lab has rinsed them good). It isn't Motel 6, but it works. And by the time you get to where you want to go through all that hassle, it really feels good. I was looking at those propane-powered in-line shower water heaters for camping, last year. Got distracted by trying to come up with a homemade outfit, then summer came along and didn't have to worry about it. Sigh, and here comes another winter, but this year there is the wood stove for keeping a pot of water hot. Luxurious. I guess a lot has to do with how much you're going to need how often.

 

[HuntingHawk]

You really need to do some serious research because you are really off on everything you are saying. IF you have a well dug how are you getting the water out of the well?

Why are you planning to use baby batteries instead of larger deep cycle batteries. Do you know that batteries shouldn't be drawn below 50% charge or you will kill their life cycle? A 125AH deep cycle battery will only give you 62.5AH available power.

How much power do you expect to get from 300watts of solar panels per day in the winter? Plan to keep snow off them? Adjust panels monthly for the angle of the sun? Sun varies by 5 degrees every month.
Best case scenario you will get 15AH from your panels & that won't be consistent threw the day. Even in summer it takes time to evaporate the dew off the panels before they start working well. Even humidity in the air will slow down solar. Best case scenario in winter you might get 45AH out of those 300watts of panels.

Do you understand an inverter takes 12VDC & changes it to 120VAC? With a highly efficient inverter that is 10:1. So for 1 amp of 120VAC out of the inverter you are drawing 10 amps from the batteries.

 

[Mad Trapper]

Put a large container on the woodstove that has a tap so you can draw water off as needed.

Showers will consist of gettting wet and soapy followed by a rinse. Lived this way for several years when it was too cold to just use the brook. All water got preheated on the woodstove for cooking, dishes, or laundry.

 

[graynomad]

Not a chance, even people with huge solar systems seldom do jobs like heating and cooking with electricity. It can be done of course, but I've never seen anyone do so.

3kw x 20mins is 1kwh, in theory your 300w panel would replace that in ~3 hours but 300w panels are never really 300w (most manufacturers multiply the open-circuit voltage by the short-circuit current which is cheating). Better to look at the current produced by the panel at the max power point, then divide that into the 25A required by the heater and get a better idea of the solar time required to replace the power (then add 10-20% or more for loses in the system, for example if you take 1Ah from a battery you have to add a lot more to get back to equal, maybe 1.1Ah, it depends on the battery type).

(6) 35aH batteries for a total of 210aH.

Why not buy a single 210Ah battery?

 

[HuntingHawk]

I've a 520watt solar panel system & live in Florida. Three 125AH batteries. System has been running for a little over three years. It operates a 5cuft chest freezer plus some lights & a TV. Very seldom in the chest freezer as its for emergency supplies & to be able to make ice in the summer. Panels angles are adjusted once a month for the sun's angle.

I'm at 30 degrees & the angle is adjusted between 15-45 threw the year. 5 degrees per month angle change is roughly 16-50% possible loss per month versus fixed angle panels.

 

[Kauboy]

Anything with an electric heating coil is going to be too much to maintain on solar alone.
Sad, but true. The amperage draw just doesn't play well at all.

Your best option will be to use fire. Simple, abundant in most places, and usually cheap.

There is a vid on YouTube of a guy who rigged up a copper pipe coil to a water tank.
He wrapped the coil around his wood stove's chimney, or place it inside, can't remember.
As the temperature rises, it siphons the water through the pipe, heats up in the coil, and goes back into the top of the water tank.
The entire system used zero electricity and brought an entire water tank to proper temperature in less than an hour.
I'll see if I can find it and post the link.

EDIT: Found it. There are a lot of examples out there, but this one is the particular one I liked:

 

[paraquack]

First off, as an avid RV'er, the idea of a bunch of small batteries I don't understand unless you have to backpack them into the cabin. As HuntingHawk said, the 105 AH golf cart batteries will much more reliable. I had the same set in my RV for close to 13 years.
As far as heating water, that's going to be a real dilemma. I think you're going to have to learn to take sponge baths. The only other solution I saw but on a small scale was and old fashion oil cook stove that had a water tank built into the top. The heat going up the chimney would heat the water. It had a spigot on the side. Along the idea of what Kauboy was talking about but factory made.

 

[James m]

The first thing I thought of was the instant hot water dispensers for under the sink. 2/3 gallon tank and 110 volts. For 200 degree water. Some are over 1,000 watts but some are 500 watts. No I'm not going to make that math problem work in my head.

Next thought was the hot water from a water cooler. The parts mostly. I think those go up to just above boiling.

My third thought was to wonder how many batteries it would take to run my 240 volt well pump and hot water heater down stairs. Then the Tennessee valley authority.

 

[HuntingHawk]

12V solar system to operate a 240VDC well pump is mind boggling. First, you have a 20:1 ratio & that isn't figuring any inverter losses. My sta-rite pump uses 11amps at 240VAC. Simple math, it uses 220AH from the batteries. Figuring 5amps from a 90 or 100watt panel, that would be 24 panels to keep up with it.

That is a sta-rite 2hp, three stage, 240VAC, 11amp pump drawing from 117ft on a 2" well.

 

[HuntingHawk]

BTW, the inverter I would need would cost $500+

 

[James m]

Just duct tape a few hand warmers to one of those solar shower bags.

 

[HuntingHawk]

An option for a shower is one of the 3 or 5 gallon solar water showers. Winter, you can add cold water to it & then mix some hot water off your heat source & hang it in the shower.

Cistern or water tanks in the basement for water storage. Fed from the roof (rain collection system). Might need a window access to add snow or ice in the winter if you run low. Then a simple 12VDC shurflo water pump like used in a RV to move the water. You will need a filter system for palatable water.

 

[Gunner's Mate]

Electric is the worst or least efficent way to heat water an on demand propane Water heater would be the most effficent way of heating water cheaply, quickly and econmically, the second would be a DIY wood fired bolier system which could also heat your cabin this does require firewwood, I have a friend in ohio that heats his entire home and his water and has converted a dry to the system to be able to dry clothes, FYI a really smart guy could also use it to run a steam engine which could run an Altenator/Generator to charge your baterries.

 

[Dubyagee]

Bury a long hose under a compost pile. Or black hose on the roof.

 

[amaxonor]

Well after reading what's been said on here, I think I'm going to opt out of trying to use electricity to heat my water. I'll probably just wind up heating some water on the wood stove in the beginning while I look for some other methods of heating, be it hoses under compost or on the roof, etc. I still have to figure out what appliances I'm going to have in the cabin. The one that I can't see any way around is going to be a fridge/freezer so I still have to do some math to figure out how many batteries I will need+solar panel upgrade to be able to power the fridge/freezer and some lights.

 

[Wildguide]

I did a good deal of climbing in Ecuador SA and the locals would use the large water tub with black hose on the roof and it worked pretty good.

 

[James m]

Maybe look into a mini fridge made for a camper. I don't know if they run off of 110 volt or 12. Know my uncle had one but I don't recall how it was powered.

12 volt coolers for use in a car. Option #2.

You said Pennsylvania. I live there now. Abouts how far ya going out.