Realistic off grid system?

Ethan Brush

I have a family member who is considering buying a piece of property and building a house, however they will not be able to get grid power there.  I am trying to make sure they have the full picture of off grid living and not having grid power.  Its a bit of a red flag to me, someone who is thinking of going off grid just because they cant get grid power, not because they want to. I lived off grid for 10 years, but am now grid tied with solar.  So I feel that I know what its like and am telling them to proceed with caution and trying to make sure they are fully informed about what they are getting into.  I may help them design and build the system if they go thru with it.  I just want a reality check on a few things.  Like I said I lived off grid for years and have done some small simple systems, but I havnt really done any larger scale off grid homes. They talked to a solar contractor who is saying they can use mini splits for heating and that they should be able to only need about 10 gallons of generator propane per year.  This is central NY state.  This seems very unrealistic and throws up some red flags on this contractor.  Am I off base?   Sure we would be talking a large array, probably 10-16 KW, but I am skeptical of heating with mini splits off grid during those short dark winter days.  Sure sometimes, but I dont think you can count on it.  Thoughts?

wellbuilt

10 gallons 🤣 the solar guy never tells you about the snow . 

 I am 50 miles west of Kingston in ny 
  The solar panels 
 last year I used 15 gallons of gas this year was 5 gallons a week for 10 weeks the solar was iced in . 

So 50 gallons
 it’s possible to clear the panels of snow but up here it just snows every day 
 and it takes all day for a inch of snow to melt off 🤷🏻‍♂️So  I just fire the Honda every morning before coffee . 

 I use about 15% of my battery over night so I’ll just charge a little every day and give it a good charge every 4 days or so 
 I use 16 golf cart battery’s a out back flex power 1 3648 inverter charger 120volt 4500 watts of solar mounted on a iron ridge 1000 . 

 I have a radiant heat floor  and there is no need for A/C the hose stays 67o all summer long . 

  I just heat with wood now I see a lot of -0 and high wind and being on the top of a mountain 
 

 

 

Photowhit

Sounds very unrealistic to me.

I think you have a good handle on it.

Starting from scratch, you CAN build a very efficient home. I don't use generators, but heat with wood. Suggest they look at heating with gas...

Ethan Brush

So let's get out of the way that anything can be done off grid,  it's just a matter of how much it costs.  So let's say this is a smallish house (1500 sq feet?) .  New construction with spray foam and good windows. Lets say cooking is gas, and hot water is gas  (but diversion used in times of plenty.  For heat, just a quick and dirty estimate from my house which is heated by electric now, say it needs 6kw of electric heat. That's about a 1.5 ton mini split.  Now calculating the batteries to run that - and assuming we can tolerate some wood stove and/or generator running during the worst days - is the hard part.  I will say this guy said 30-50k for the system. Does that change anyone's position?

Photowhit

Ethan Brush said:

So let's get out of the way that anything can be done off grid,  it's just a matter of how much it costs. 
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Does that change anyone's position?

So trying to figure costs will get very difficult, December with an array with great orientation, you get 3.24 hours of direct sunlight a day.  Long storms of 3-4 days with little or no charging.

Loads of 6 kWhs and some other fridge and water heater, light add another 3-4 kWhs, Say 10kWhs, in 3-4 days of no sun, you can look at 40 kWhs out of storage down to 50% for a 80 kWh battery bank? That's some huge battery bank....

...or you run large forklift battery with support generator when you do a very large 48 volt forklift battery common ones top out around 60 kWhs ($10.5K +/- don't really want to price out 60 kWhs in lithium or even AGM) and charge when you reach 50% State of charge or when the bank has been below 75% for more than 48 hours. Now there is a lot on interaction for 'new to solar' people. It can be automated a bit but I suspect this is going to use a lot of gas and we are still only using 'pretend' loads.

wellbuilt

Well my system cost 10k ? I had to put it in my self . 

 I allso have 4500 watts of extra panels and a second fm80 charge controller That I bought and is not installed yet . 

  I think that the Utilities for home are costly and it’s not really worth building a 1500sf house . 

 The home should be around 2000feet . 

 My place is 2800+  The cost for the extra 500sf is marginal  . 

  I’m pushing 60 years old and I’ve never lived in a house with Central heat  I’ve been splitting wood for 50 years . 

 I would just use 2x8 walls and r 30 bat insulation you could add Dow board on the out side .
 R60 insulation in the ceiling . 

 I insulated 3600 ft.² for about 1000 bucks in insulation and plastic sheeting.
 It took us 3 days . 

 Spray Foam is very techy and cool but way to much money . 

 The spray foam guy wanted 10k 0for 2” of foam in the walls and 3” on the bottom of the roof . 

 

  Electric heat in ny is not going to work. 
 I get 2.5 sun hours  a day at best in December .  And nothing when it’s snowing AND ITS ALL WAYS SNOWING . 

 It seams to me the price go’s up by 10k 
 my system is 3600watts  I can double it for 7200 watt and 20k in material . 

 My battery’s where cheep 430 amp hours for 1600 bucks 
l16s with 760amp hours cost 2880 at the time . 

  My system charges with a 2800watt Honda . 

 My inverter charges @1700 to 1900watts 
  15% of my battery’s is 3300watts so if  I charge for 2 hours I get all most to full .  

   I’m not sitting in the dark huddling under a blanket 
 I burn about 15 /20 splits a day the house stays 70/75 o day time I don’t burn over night 
 in the morning the house is 65/68o  
  I could not of put the power system with out the guys on this forum 👍 
 where in ny you’re are you  it make a big difference in the amount of sun you get 

706jim

In short: Panels are cheap, batteries are expensive.

MrM1

Sounds like a job for DIY LifePo4 ... LoL

wellbuilt

Hey your set up looks really good , I just looked thru your build picks since I just can’t sleep 💤👍

Ethan Brush

So I am an hour west of Albany, near cherry valley/sharon springs.  Yeah the sun hours in December is awful.  

So just to be clear, That 6KW figure I threw out was for resistive heating, but with a good mini split the COP would be somewhere around 3 so its only taking 2KW of power to make 6KW of heat.  Using a mini split for heat does seem like a good idea, but only for when you have energy to burn, which presumably will be any sunny day.   But of course you will need something for the night, and dark snowy days, and some sort of control scheme if you dont want to just turn it on and off manually.

Dave Angelini

You are on the right path for heating! A split is great, but becomes a secondary source where you live for alot more than December.

wellbuilt

O cool, I built some homes in Cherry  Valley in  1983 we stayed at a hotel there ( the only one ) spent a lot of nights in the little bar down stairs .
 Cherry valley has a lot more sun then my place. Im about 40 min south of you .

I think if you built on a insulated slab with radiant heat you won’t need over night heat my floor hold heat over night . 

 I don’t even load the stove up before  bed . 

 I don’t have a heat source for my floor yet . 

  In our area we have ok sun till around thanks giving after that its really dark until the last week in January . 

   We get Lake affect snow witch means it snows every night 1 or 2 “ and it takes until 100 pm to melt it off  , so it kills 
  Production. 

   I don’t need a/c at my place in fact I’m opening the doors to warm the place up in July 
    You may not need ac in your location I burn wood 10 months a year. 

      What Seams to happen is people install a wood stove for temporary heat and emergencies and then they get hooked . And they just keep burning. 👍

BB.

If you split your array (and/or slightly oversize it) to 1/2 facing south east, and the other 1/2 facing southwest, you can get "more hours" on charge vs just one full array facing south.

Ideally, each array plane should have its own MPPT charge controller (so each MPPT tracking circuit/controller is dedicated to each array).

You can play with one of the array calculators and see how much overall harvest you lose with SE/SW arrays vs all south (it is usually not too much over sizing):

http://www.solarelectricityhandbook.com/solar-irradiance.html
https://pvwatts.nrel.gov/

Very nice when time gets short in winter--Lead acid need time on charge (absorb phase) to complete charging. Lithium Ion charge pretty much to 100% Sate of Charge on nearly 100% current... And absorb time is either near zero or less than 1 hour (check vendor specs.).

FLA batteries need time to charge (10-13% or so), plus 2-6 hours absorb (50% depth of discharge ~ 6 hours of absorb).

Can also go with 2 axis trackers (longer time on sun and more harvest per x,xxx watt array)... Dave A. likes those very much--And his experience is a couple squirts with a grease gun once a year in the actuator Zerk fittings keeps things working.

-Bill

wellbuilt

There you go , this is for  west Albany it dosent start looking bad until nov  then January is looking better.
  This is facing south @ 47o  we get more sun in the morning . 

 My number are not that good

   
 

Ethan Brush

Cool, thanks for the input.  Yeah I think the radiant slab idea is a good strategy to hold heat during the night.  Also like BB's idea of the split array, presumably this would be very "over paneled" so and of course being off-grid annual energy production isn't really the goal. I know this is a very general discussion, I'm just trying to get a feel for inconvenience versus cost to give them a realistic idea of what they can expect living off grid.  Like I said, I am just very cautious of people whoare thinking of living off-grid not because they want to but because they have to

That guy said a 30 to 50 k $ system, which could be a pretty serious system, but still seems a little optimistic considering his talk of using mini splits for heating, heat pump for heating domestic and 10 gallons of propane per year 

Dave Angelini

I think if there is a firewood source, one would be a bit crazy, living offgrid, to not install a quality EPA woodstove. You already will be tied to a genset and the only way to minimize it is not using much electricity in those bad months. Once burning temp is up, there is very little smoke. We walk a mile around our place and never smell it unless it was just lit. Being tied to propane for heating is not Offgrid in my opinion. I use the Offshore Cruising mentality of 3 back-ups for each of the important systems offgrid.

 Over paneling can help but there will be days where we are talking about 8KW of solar and more to get any benefit. Virtual tracking in winter is a losing game compared to a real tracker that can be in the right spot for an hour of the short day. Pointing south is going to be 2nd best in your location no matter what the charts show for winter. At my home we get the winter special, and the last hour of solar, a cloudy sky clears and the KWH's are there for harvest. I say this as you really do not know what a particular location will do unless you study it for a year, first! The charts often measure in the wrong location. Useful but....

If you use a spit, it needs to be the best model in the make to minimize electricity use. Most of the 100's of offgrid homes I help out on use a 9,000 to 12000 BTU from the best. Brands like Mitsu, Fugitsu, LG and other name brands. Look for SEER of around 30+ and that will indicate how well it can heat. The Fugitsu is 3+ times more efficient than resistance heating. HPSF of 14.2. Not cheap but amazing at sipping current.
 https://www.acwholesalers.com/Fujitsu-09LZASH1/p106472.html

You are right about the folks that are living offgrid for the wrong reasons. It can often end in disaster and I call it Offgrid Squalor. Out west because of the wildfires, Fire and Building departments and enforcing code on properties that they use to look the other way on. You can't live in a trailer more than 2 weeks in a 3 month period is the law in many places that can enforce.

Do not forget property value if not mentioned. Offgrid will be less when it is sold. Build something that is marketable to many people.

Take a look at them and make sure both eyes are open