I'm in the preliminary stages of getting an off-grid system put in (hoping to have it up and running in September) and just have a few questions regarding battery storage capabilities.

I'm looking at a 12-panel pole mounted system which guarantees 4800kWh/year. Right now, I average about 500kWh/month, but, admittedly, I waste electricity like it's going out of style. So I could, with a little discipline, easily get that below 400/mo which should be covered by the above system without a problem.

I'm curious, though, how many batteries I would need at a minimum and if I can simply just add more batteries for increased storage for winter time when we occasionally get socked in with inversions.

When setting up these systems, do the contractors take things like weather into account and that's how they estimate how many batteries are needed?
How much juice do those batteries hold? Are they Lithium ion? Standard deep cycle?

I'll be able to get these answers from the contractor when he comes out to survey my place, but I wanted to get a little information beforehand so I don't sound like too much of an idiot and also so I don't get taken by a salesman (not that I don't trust the guy).

i don't have the info you need. But just a question. I assume you are wanting independence from the grid. Probably still use it though. It is not about saving $, right.

I am pretty sure it is way cheaper to conserve as best you can and stay on the grid. Verse's spend the kind of $ you are going to invest to try to power a fully functional modern home.

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Originally posted by old rugged cross:
i don't have the info you need. But just a question. I assume you are wanting independence from the grid. Probably still use it though. It is not about saving $, right.

I am pretty sure it is way cheaper to conserve as best you can and stay on the grid. Verse's spend the kind of $ you are going to invest to try to power a fully functional modern home.

Several goals actually. Ultimately, it will save money, but that'll take a decade or two. Primarily I want it for peace of mind. After reading Ted Koppel's research, I don't trust our grid as far as I can throw it. I want/need the ability to be independent from it.

Shorter term, we have more power outages around here than any place I've ever lived. At least once a month there will be an outage lasting anywhere from a few minutes to hours. I do have a dual fuel generator set-up and enough propane to survive probably for a few weeks, but quite frankly it's a bit of a PITA, and noisy as hell.

An off-grid solar set-up will solve these problems. I'm looking at roughly $19K right now (before rebates and tax credits of approximately 30%). So, yeah, it's somewhat spendy up front, but never being without power is comforting and worth the cost to me.

Don't discount the maintenance, expense to maintain and headaches. Combine those and $19k will be cheap.

While I understand. The power grid is dam reliable. 20 years to pay back. Come on. Think about the technological advances coming in that time frame.

I mean, sure. Go for it. The guy pedaling it is counting on you. But it is really a crazy idea and what a waste of money.

Now if you did not have access to grid power then I could understand it.

Or if you want to set up a tiny back up system for lights and minimal electricity, fine.

To each his own.

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The power grid is dam reliable.

And, no...it's not.

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Originally posted by Gustofer:
To each his own.

Amen brother. Good luck with it.

Right off the bat, there's the fact that at night, during cloudy weather, and during very cold weather, performance will be nonexistent or highly diminished.

PV panels are typically rated for output at 80°F, and typically lose about 50% of that rated output by simply reducing the temperature to 40°F. Output continues to drop as temperatures do, so you'd want to size the system for that scenario for it to do you much good in the dead of winter, which to me, would be the time you'd really need it to back up the grid. Most other times of year, no power is an inconvenience, but in winter in the north, it's a lot more serious than that.

If you were someplace like Arizona with a ton of sunny days, a more southern latitude (getting you more daylight hours available in which to produce electricity), and likely an overall warmer climate, it might start to make sense. In Montana, probably not so much. Wind might be a better idea to harness there than the sun.

Then there's the maintenance: keep the panels clean for peak efficiency, blah blah... Don't forget the extra expense of specifically insuring them.

I actually considered installing a system here in lower Michigan, but running the numbers, even with the sizable discount I had available, tax credits, and other things, I still couldn't get a sufficient ROI to justify it.

Yep, well said sandman.


It is not reliable? According to who, Ted?

For every idiot who say's it isn't. I can find two who say it is.

Gustofer, what's the wind like on your property? They make small wind turbines. If I was off the grid, I think I'd want more than one source of power.

I looked hard at solar here when we built this house. The ROI is not there in my mind, then add in maintenance, battery replacements, etc... the whole house system was just not worth it.

I do have a couple of smaller panels, a couple of Marine batteries (they also get used in the RV) and ran wiring for 12 volt lighting. It won't run the AC or the heat, but we will have lights.
I have a duel fuel Generator for the well pump, water heater and a window unit if we need those and put in a wood burning stove for heat in the winter.

Paging member offgrid. As I recall he has experience in wind and solar, in Colorado. There used to be a post that showed his windmill and a thread or two where he discussed.

quote:

Originally posted by Gustofer:

Shorter term, we have more power outages around here than any place I've ever lived. At least once a month there will be an outage lasting anywhere from a few minutes to hours. I do have a dual fuel generator set-up and enough propane to survive probably for a few weeks, but quite frankly it's a bit of a PITA, and noisy as hell.

We were in the same boat. We used to lose power at least once a month, sometimes for a couple of days at a time. We are also on a well so when power goes out we're without water also. Additionally we had some family members who were not in great health and couldn't deal with loss of electricity easily, oxygen generator, etc. Our solution was to purchase and install a 30kw propane generator that handles everything in the house. It automatically switches on when we lose power and once a week it runs for about 20min as a maintenance routine. I don't remember the cost exactly but it was a good bit less than $19k. I think it was around $13k but that was several years ago.


As far as solar goes, it really amounts to what you want. Running a modern house with all the modern amenities is hard with solar. I have a friend who could easily make it on a small harbor freight sold system, but to call his lifestyle spartan would be a gross understatement. He lives in a very temperate region, is retired and hikes an enormous amount of miles in a year, doesn't use AC, and since he's often asleep by 8pm most nights anyway, rarely needs much lighting.

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Originally posted by 46and2:
Paging member offgrid. As I recall he has experience in wind and solar, in Colorado. There used to be a post that showed his windmill and a thread or two where he discussed.

I remember that thread,

very good write up with pics to show what he had going on

quote:

Originally posted by Gustofer:
I'm in the preliminary stages of getting an off-grid system put in (hoping to have it up and running in September) and just have a few questions regarding battery storage capabilities.

I'm looking at a 12-panel pole mounted system which guarantees 4800kWh/year. Right now, I average about 500kWh/month, but, admittedly, I waste electricity like it's going out of style. So I could, with a little discipline, easily get that below 400/mo which should be covered by the above system without a problem.

400kwh Month = 13.33Kwh per day. Now do an energy audit and see if you can make it on that. You might be surprised.

https://www.cpi.coop/my-accoun...ne-usage-calculator/

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I'm curious, though, how many batteries I would need at a minimum and if I can simply just add more batteries for increased storage for winter time when we occasionally get socked in with inversions.

There are a couple of ratios out there for batteries to panels and it really depends on what zone you are, system voltage, depth of discharge(very battery dependant), and battery voltage. It also isn't panels to batteries, it is more like watts(panels) to amp hours(batteries) with voltage in the mix too.

https://www.wholesalesolar.com.../battery-bank-sizing

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When setting up these systems, do the contractors take things like weather into account and that's how they estimate how many batteries are needed?
How much juice do those batteries hold? Are they Lithium ion? Standard deep cycle?

Battery choice is relative to all of the above and will be sized to your panels, charge controller, and inverter. As long as your charge controller and inverter can handle it, you can ass more batteries and panels. Everyone has their opinions on lead acid vs. AGM vs. Lithium. For now the Lead acid and AGM are the most affordable. Many people like lead acid because you can monitor them mechanical with a hydrometer. Many like AGM because of the no maintenance aspect. Everyone wants lithium, but they are extremely expensive.

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I'll be able to get these answers from the contractor when he comes out to survey my place, but I wanted to get a little information beforehand so I don't sound like too much of an idiot and also so I don't get taken by a salesman (not that I don't trust the guy).

I would do a metric sh1t ton of research and due diligence before signing any contract.

I'm moving in 15 month and will be off grid in the middle of the AZ high desert. I have got two quotes from different outfits on negligibly identical systems. Their prices pre-installation are about the same, but their individual components vary wildly. Neither seems to have a good answer for why. OTH, I can source all the components from the quoted systems myself for significantly less from two places on the net.

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Originally posted by Sigolicious:
I can source all the components from the quoted systems myself for significantly less from two places on the net.

Can you tell us the names of the two places you prefer? My biggest issue is in finding sources I can trust, and in getting far enough up the supply chain so DIY makes sense.

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Originally posted by deepocean:

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Originally posted by Sigolicious:
I can source all the components from the quoted systems myself for significantly less from two places on the net.

Can you tell us the names of the two places you prefer?

I could use any of the following to get anything I will need, but I would prefer the first two as they have great people who will answer questions.

http://www.backwoodssolar.com/

https://www.solar-electric.com/


Never spoke to either of these two, but they have good selection and pricing.

https://www.wholesalesolar.com/

https://www.bluepacificsolar.com/

Thank you for posting those links.

Yes. While we have 12KV three-phase running down the valley supplying the wells, the barn, and the entry gate, our house is off grid solar. We're too far away from the 12KV line to pull 480V up to run the house ~3,000', and it would be ugly and a maintenance hassle running 12KV overhead. Undergrounding would have been roughly $300,000, so that was out of the question.

In the process, I learned a lot about off grid solar. I wouldn't describe what I think you are looking to do as off grid solar, at least that isn't what I'd do in your shoes. I'd put in a grid tie system with battery backup.

In no particular order, here are the things I learned about off grid solar:

Most contractors don't know jack about off grid systems. They do a whole lot of grid tie, as that is where the rebates are, but they don't do off grid systems. If they claim to know off grid systems, I'd ask to see off grid systems they have installed and talk to some satisfied customers.

Lead acid batteries don't make anything like rated power when you hit them with a high current draw. It sucks them down really hard, more than simple math would lead you to believe. Supposedly, Lithium Ion batteries are coming and they are going to be the best thing since sliced bread, but last I checked, they weren't there yet. They may be now. LI batteries can and do put out full output without suffering like lead acids do. This matters to you if you have high current loads.

When you add new lead acid batteries to an existing bank of lead acid batteries, they get sucked down to the level of the old batteries. I don't know if this applies to LI batteries also, or even if LI batteries are an option yet. If you think you are going to need more power, put it in up front

There are some slick systems out there, both Outback (what we have) and Xantrex that I am aware of. There may be others.

A transfer switch is a beautiful thing. I ended up wiring a manual one in between our Kohler 8KW propane powered generator and the generator input on Outback system. On the other side of the switch is a 240V 50amp four prong outdoor outlet and I built up a cable with the male version of that plug on both ends. One end stays plugged into the outlet. Typically the cable is hanging looped over the transfer switch. When needed, I can bring our arc welder/10KW generator up, plug the cable into it, throw the transfer switch, and we are in business.

Being your own electric company, water company, and waste disposal company can be a pain, but it does have its satisfactions. More than once we have heard about local power outages from friends that we'd have otherwise been clueless about. Also more than once, the first indication of power problems has been when the front gate wouldn't open.

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Originally posted by slosig:
I'd put in a grid tie system with battery backup.

I think this may be the better option for now. I just want the ability to be off-grid if need be.

As I understand it though, there are different inverters for the two. Do you know if this is correct?

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Originally posted by Gustofer:

quote:

Originally posted by slosig:
I'd put in a grid tie system with battery backup.

I think this may be the better option for now. I just want the ability to be off-grid if need be.

As I understand it though, there are different inverters for the two. Do you know if this is correct?

There may be, but the Outback system that I have can use line power if it is available. It also automatically starts the generator if the battery voltage gets below configurable set points. When I was trying to put together a 240V UPS for the front gate (PG&E was really flakey for a while there) I found a Xantrex unit that basically did everything out Outback system does all in one box (which would better fit the gate application) the problem was it was a 60amp system which was a lot more than what I need for the gate. The 60 amp 240V Outback system does a nice job running the house. The only time we run into a problem is when we try to run the hot tub (which pulls 5KW when heating) and it isn't a good sunny day.

ETA: The Outback system has logic to not backfeed the generator. I suspect that it will backfeed the mains (sell power) and I'd guess that is what you would want. I'd think you'd want a disconnect between the mains power and your solar system. Normal situation it would be connected, you'd sell excess power back to the power company when making power once the batteries were topped off and pull off the mains when not making power. When there was a power outage though, you'd disconnect so you weren't backfeeding the mains and your system would automatically use batteries when not making power (or not making enough power).