14.4 KW solar, 40.96 kWh backup, 2 solark 15k inverters, off grid family home, doable or delusional?

[ksmithaz1]

2 cents:

I'd get three (3) 240v/50a inverters in parallel such as the EG4 or Sol-Ark Units, purely for demand/redudancy. The EG4 units currently do not support staying on when one is down. If the Sol-Ark's do that is a consideration verify that part of the operation. By the time your project gets going this may change. You'll want 90 KWH of batteries, and around 20KW of Solar panels. I would design a small-ish outbuilding to hold all the solar/battery/electrical and a 10KW generator. Run 2/0 feed wires in conduit up to a 150A "sub"-panel on the house. Build high-efficiency as you have outlined. Leave room /plumb for another 60KWH of batteries in your outbuilding ( 5 equipment racks ), and another AIO (These beasts are pretty big). Get your propane but feed it to the generator. I'd run a pellet stove(s) inside for emergency / aesthetic heating Maybe in the L/R and Bonus Room, or perhaps LR and garage) or a wood fireplace if it gets too cold for a modern heat pump.

You may need to bump your solar panels for battery fill considerations, cover the roof figure out a ground-mount location for some extra as needed. I'd go all-electric appliances, including the dryer and an electric traditional 50Gal tank style HWH, and an induction range. As far as the Low vs High Frequency my pair of EG4's seem to work just fine starting a crappy Goodman 4T HVAC with a Magic Start. It worked without the Magic Start but really dimmed the lights, so HF should be fine if you engineer for it from the get go. The well pump will be the trickiest but I don't think it pulls as much on start as my HVAC did when it was 120 outside this July and no magic start. You might look into a smart electrical panel at the house.

Don't over-think it. You can also build it lower and scale it, just plumb for the extra. You could start with 2 inverters, and 60K of batteries maybe 10K of panels, and see how it goes. You can add panels if the batteries are not getting charged on lower production days, add a rack of batteries if your overnites start kicking on the generator too often.

Sounds fun, good luck. I finally kicked the grid habit a week ago with an additional 30KWH of batteries (see my sig) But I do HAVE the grid if I need it.

 

[Tamooj]

We live in South Louisiana, but are planning to build a house in North Louisiana on owned property, if...

This is very similar to our setup, (we're in East Texas) so here's some thoughts to consider. Your mileage may vary.

1. Go with a dual fuel hvac. Heat pumps/inverters are amazingly efficient but suck when it gets below 35°. Also, if it's cloudy for a few days they will drain your batteries fast. Whereas propane heat as the backup only needs the 400W blower.

2. We have 36kwH of storage and I'd double it if i could.

3. If you're going with a pedestal consider getting a two axis tracker. That basically adds 35-45% to our PV production, and we've never regretted it.

4. Get a system you can monitor and control locally (ie when there is an internet outage).

5. Your batteries will need to be protected against heat and cold, which means good insulation and a minisplit. I used a shed for the inverters+batteries, which I've had to upgrade several times to keep the batteries healthy. On the plus side it's a great place to keep plants during the winter - just add a growlight and timer.

6. Geek out on monitoring: Nothing sucks more than the lights suddenly going out on a cold day and wondering why.
We have dual SolArk inverters and wired them to a local device that displays power usage and state of battery charge on colored LED lights in the kitchen (and a graph on our phones) This lets us yell at the kids when they run the dryer when it's cloudy or at night.

7. Consider a smart electric panel which lets you turn on/off circuits as needed.

Good luck!

 

[ksmithaz1]

We have dual SolArk inverters and wired them to a local device that displays power usage and state of battery charge on colored LED lights in the kitchen (and a graph on our phones) This lets us yell at the kids when they run the dryer when it's cloudy or at night.

I considered this, and may need to revisit this summer on the weekends. Was this a commercial device or something you home brewed? I'd love to have a red-light/green-light setup in the laundry. It's so darn sunny here in the desert it's rare to have to go more than a day without significant sunshine, but the electric load in the summer is just brutal, and I'm not sure 60KWH is going to make it thru the night unless it's 100% at 1700. It's this or another 30KWH of batteries, or perhaps just lock up the little woman... She pulled a "one more load" at 1800 yesterday after I charged the car. Pulled the batteries down to 11% before solar started to help out. Not a problem this time of year.

 

[wheisenburg]

A few things:

1. Consider going with 2*6 construction on the outside walls. This allows for nearly twice as much insolation. The extra money you spend there will be more than made up for by not having to build as big of a solar / battery system.
2. Switching to a gas drier now will also save you money. The additional inverter power / battery needed to run a power hungry electric drier is more expensive than getting a new gas drier.
3. You might consider Schneider inverters. Even though they might have a lower watt rating, their ability to handle surges and out of balance loads means it is nearly impossible to trip these offline. On my system the three 100 amp batteries will trip before the inverters. If you are running large motors for your well and air conditioners, the Schneiders will easily handle the required surge current. You should get a soft starter for your A/C units in any case. The Schneiders are very reliable as far as the hardware. The software works fairly well for off grid. Some of the features like grid sell are difficult to setup, but not relevant to you. Their PDP panel allows the inverters to easily be stacked and wired together. Two should easily run the house you are considering.
4. With 500 gallons of propane, and the need for generator back up, spend the money required for an auto generator start system. The kind of generator permanently installed on a pad. It is perfectly acceptable to occasionally run the generator for an hour or two a day on cloudy days to charge the batteries. This will be far cheaper than adding the insane amount of batteries required to get through a week of low solar production.
5. Consider getting two smaller A/C units (2 ton) rather than one large one (4-5 ton). First it will give you some redundancy. It seems like it can take weeks now to get an A/C or furnace fixed. If one unit goes down, the other can at least keep the house livable. A couple of box fans can easily circulate air from one part of the house to another. Also it reduces the amount of startup current needed.
6. As some people mentioned, you can get ducted mini-splits that are installed in attics. One issue with some of these items is that while they are cheap, they are basically disposal. There may be no replacement parts or trained service techs available. If they quit working, you need to replace them. Often, professional HVAC people aren't going to want to work on these. They prefer to sell you the expensive high margin products that they normally deal with.

 

[ksmithaz1]

1. Switching to a gas drier now will also save you money. The additional inverter power / battery needed to run a power hungry electric drier is more expensive than getting a new gas drier.

Because the price of propane is going to be stable for the next 20 years? Or because you found a woman that doesn't throw her clothes in the dryer first thing on a cold winter morning to warm them up before putting them on?

IMNSHO if you are going solar, I'd go all the way electric and only run propane/other as a last resort. $500-$1000 for a gas appliance. $1500 for another 25A inverter to meet demand. The battery is the big deal, but even though the thing really uses juice, I'd roll it and plan for some extra battery. Panels are cheap. The idea is to not pay the Gas company or the Power company.

 

[wheisenburg]

IMNSHO if you are going solar, I'd go all the way electric and only run propane/other as a last resort. $500-$1000 for a gas appliance. $1500 for another 25A inverter to meet demand. The battery is the big deal, but even though the thing really uses juice, I'd roll it and plan for some extra battery. Panels are cheap. The idea is to not pay the Gas company or the Power company.

I have a grid tied system with full net metering. So for me, yes I do have an electric drier and I have no plans to replace it. Driers along with water heaters are energy pigs. Now your situation in Phoenix is better than mine. You are farther south and there are very few long periods of cloudy days. In Louisiana the situation is probably somewhere between us. Because this is a fully OFF GRID system, just pulling a few KWHs from the grid to dry a load of laundry is not an option. Putting off laundry for a week because it is cloudy may not be an option either. For someone trying to live a normal life in an off grid home, running out of power because you needed to do laundry really isn't an option either.

My situation is different. With full net metering I can push power to the GRID during the day and pull it back later for free. My batteries are there just to get me through power failures without extreme inconvenience. If we get a longer outage during the winter when my PV generation is consistently less than consumption, I will need to run a portable generator once or twice a day to top the batteries off. Yes pulling out and hooking up a portable generator is a pain, but this works for me. It is a situation I can live with if I have to in the event of a power failure at the worst possible time. I don't think this is acceptable for someone fully off grid.

For someone fully off grid and just looking for a feasible system, I think what makes the most sense is to design the system such that it can supply your house 95% of the days. Then supplement that with a generator about 15 days a year. Getting to that 95% is going to be significantly cheaper if the overall load on the system is less, so reducing overall consumption is part of the solution. This is especially true with batteries. I would make sure the system has plenty of KWs of inverter capacity, especially surge current if driving a well. For battery storage, I would make sure I had 1 day of storage for a winter day, and maybe a little more to make sure I can run A/C after we lose PV production in the evening. In summer you get better PV production and if it is cloudy A/C consumption also drops, so I wouldn't size this for one day of the highest energy use. Let's say we go with 30 KWHs of storage and that gets us through 95% of days without needing the generator. If you have sized the system to meet the power requirements 95% of the days, you will run the generator 15 days a year.

Now lets say that instead we double our storage to 60 KWH. That might cover us for 98% of the days. We would still need to run the generator about 6 days a year. So doubling storage will cost us about $9000 and save us from 9 days of generator use.

The cost of generating 1 KWH on a natural gas generator is about $0.20. The cost of storing 1 KWH in a battery is about $300.00. Yes the battery can be used more than once, but you won't break even until you have completed 1500 cycles. It will take you more than 150 years to recover the cost. My idea is to not pay more overall for a comfortable off grid life style.

Now if the system is undersized, the only down side is that the generator will run more than you planned. Based on experience, you could add either more solar or more storage depending on where the system is falling short. Adding more panels and possibly a charge controller or more batteries shouldn't be a big deal.

 

[ksmithaz1]

If you are off-grid, you are talking propane, not NG, but I digress. I'm on grid the next 3 days because there is no sun, and I can't go that long on 64KWH. None-the-less I still dry clothes off the batteries, because most of the time, its energy I don;t have a place to store anyway. If I was fully offgrid, I would look for 200+KWH of batteries, and a 10KW genny. The genny kicks on to charge batteries if they get below 20%, not to run the house, per-se. I would always have inverter capacity to meet demand for the house. Averaging out the Dryer and HWH in the overall scheme it's not really that significant for me, summertime AC pretty much runs 24x7, but obviously would be in a more moderate climate.

Off-grid for ~ 2000sqft I'd have ~150A of inverter to go with the 200KWH of batteries. I'd have a propane generator, and if the climate for the area demanded it, an alternate heat production system (pellet,wood,etc). You'd want about 40KW of panels, I'd go to 60 depending on the sunshine situation, and the space constraints getting them up. The objective in my case would not be 'saving money', though the checkbook does have a bottom. The objective would be independece and self-sufficiency without sacrificing my quality of life.

Frankly if I didn't charge cars or run the air my average day is maybe 40-45KWH. Even on a crappy day you generally get some solar, but it does depend on where you are. I'd really want to be all-electric. If you get enough panels at some point your batteries are full and you are producting more power than you can use and store. I think that is where you want to be, so 95% of the time you can just ignore it, but periodically you may have to run the generator if the sun refuses to shine for an extended period. Just avoid laundry when the generator is running, which should be a relatively small window here and there.

 

[ksmithaz1]

As a side note, extra panels can make up for some battery if it can either supplement enough when production is awful, and recharge enough when production is good. Extra battery can make up for fewer panels if you have enough battery to carry you through when production is low. At some point battery becomes the limiting factor.

 

[wheisenburg]

Averaging out the Dryer and HWH in the overall scheme it's not really that significant for me, summertime AC pretty much runs 24x7, but obviously would be in a more moderate climate.

For most solar systems, summer is not the time you come up short. Yes, the A/C runs a lot, but PV production is very high. I am consistently exporting power in the summer. It is winter when my system produces less than I consume. So during winter a hot water heater and electric drier really would be a significant portion of electricity use. Every time I do a load of laundry my KWHs per day spikes. Now you may be suggesting that @Themillpondhouse buy $60,000 of batteries rather than minimizing his electricity use by buying a $1000.00 drier. I think most people are looking to be a little more practical.

Yes, I know off grid people use propane. I just don't have a good estimate on the cost of generating a KHW of electricity from propane. I am quite certain it is less than $300.00.

​

 

[Zwy]

If you are off-grid, you are talking propane, not NG, but I digress. I'm on grid the next 3 days because there is no sun, and I can't go that long on 64KWH. None-the-less I still dry clothes off the batteries, because most of the time, its energy I don;t have a place to store anyway. If I was fully offgrid, I would look for 200+KWH of batteries, and a 10KW genny. The genny kicks on to charge batteries if they get below 20%, not to run the house, per-se. I would always have inverter capacity to meet demand for the house. Averaging out the Dryer and HWH in the overall scheme it's not really that significant for me, summertime AC pretty much runs 24x7, but obviously would be in a more moderate climate.

Off-grid for ~ 2000sqft I'd have ~150A of inverter to go with the 200KWH of batteries.

Insane

I'd have a propane generator, and if the climate for the area demanded it, an alternate heat production system (pellet,wood,etc). You'd want about 40KW of panels, I'd go to 60 depending on the sunshine situation, and the space constraints getting them up.

Insane

The objective in my case would not be 'saving money', though the checkbook does have a bottom. The objective would be independece and self-sufficiency without sacrificing my quality of life.

Conservation always pays. The money spent on Insane systems mentioned above would be better spent on conservation.

The quality of life can actually improve with conservation and allow for independence and self sufficiency without spending enormous amounts of money.

Frankly if I didn't charge cars or run the air my average day is maybe 40-45KWH. Even on a crappy day you generally get some solar, but it does depend on where you are. I'd really want to be all-electric. If you get enough panels at some point your batteries are full and you are producting more power than you can use and store. I think that is where you want to be, so 95% of the time you can just ignore it, but periodically you may have to run the generator if the sun refuses to shine for an extended period. Just avoid laundry when the generator is running, which should be a relatively small window here and there.

Considering your location and you don't have a large heating load during short winter days with limited PV, you really need to look more at conservation such as hanging clothes outside to dry or purchasing a heat pump dryer.

 

[wheisenburg]

You're wise to consider expansion. You can start with a minimum system and just run the generator more often the first year. Then use that data to decide if you need to expand the array, the batteries or both.

I think this is good advice.

Unless you have buckets of money, it is going to be far cheaper to supplement the solar with occasional generator use than to size the system for a worst case scenario. A properly sized system should make all the power you need on sunny summer days. It is perfectly acceptable to size things such that your generator runs once or twice a day on dark winter days to supplement the solar. Now if you install a heat pump for heating, rather than a propane furnace you will be drawing a lot more power during the time of year with the smallest solar production. You would need to take that into account. I image your winter solar production is going to be better than mine, so maybe this is feasible for you.

Part of my issue is that my HOA and roof design means my panels are East and West facing so Nov, Dec, and Jan solar production is really poor. I have a lot of west facing panels that generate far into the evening in the summer. My production actually peaks at 3 PM. I get far more production than needed for the A/C so I am exporting all afternoon. Another hint I have is that if you can design the system with say 8-9 East facing panels, 8-9 West facing panels, and the rest facing South, that will minimize the number of hours a day where you depend on your batteries. If you are going with a ground mount, you could also look into vertical bi-facial panels that run north south rather than the East West Panels. A broader, flatter power production curve means you can consume more power as it is produced. Each time you go into and out of your batteries, you lose efficiency. Each hour you can extend your production is one less hour that you need to store energy for over night. For a grid ties system with full net metering, having all panels facing south makes the most sense. For an off gird system getting a flatter power production curve is helpful.

You are really going to need a generator anyway. Trying to minimize generator run time, is really an exorcise in diminishing returns. Getting to 90% energy independence without the generator might cost X. Getting to 95% might cost 2x. Getting to 98% might cost 4X. At some point, it is time to quit throwing more hardware at the problem and just run the dang generator.

On generators there is something you should be aware of. There are really four main choices:

1. A portable generator that you roll out of the garage and plug in to the house and manually turn on. I don't think this is adequate. First these portable generators aren't designed to run in bad weather. When will you need your generator most? Also you need to change the oil once a day if you are using it continuously.
2. An air cooled standby V-twin 3600 RPM generator. This generator is going be like a Harley Davidson running at full throttle.
3. An liquid cooled standby 4 cylinder 1800 RPM generator. This generator is going be small auto engine running at highway speed.
4. A diesel standby generator. These can run for thousands of hours and are very reliable.

#2 is designed to run for a few hours a year in an emergency for a grid tied home. They are designed to last for about 40 days of continuous use if you change the oil once a week. #3 is going to be OK if you need to run it for a week or two while your inverter is repaired. If you run it 300 hours a year (30 MWHs) it should last 10 years. #4 you could run it non-stop for a year as long as you shut it down occasionally to change the oil These have a service life of 10,000 hours or more.

I think #3 might be the sweet spot especially since you already plan to have propane. These are going to be more expensive for the same KW rating than the air-cooled, but they should be more reliable, have a longer service life, and and be quieter too.

 

[wheisenburg]

Conservation always pays. The money spent on Insane systems mentioned above would be better spent on conservation.

The quality of life can actually improve with conservation and allow for independence and self sufficiency without spending enormous amounts of money.

Exactly

 

[wheisenburg]

My husband has a few years of electrical experience as a journeyman, but not with solar. He is familiar with industrial installations as well and very mechanical savvy. He feels pretty confident in the install. He also thinks I am crazy and overthinking this. I think for new build construction permitting in our area, a licensed electrician may have to make the final connections or inspect the system (our builder is willing to help us figure this out).

It ain't rocket science. A few YouTube videos and a case of beer and I gotter done. (Having a general understanding of electrical systems does help, but your hubby has far more of that than I do).

My biggest concern was making sure that the system "looked" professional. I didn't want to have wires running all over the place and stapled to the wall. I ran everything in 6" gutter boxes and 2" metal conduit. I bought all the proper tools like a hydraulic crimper and a hole punch system. I made sure all the wiring is properly sized. With the Schneider inverters and the PDP panel (that's the one without the green screen) , the Schneider PDP panel contains all the required breakers and connection points to hook together the multiple inverters. The PDP panel is pre-wired with one wiring harness for the first inverter. You just need to hook the wires (which are labeled with ferrules pre-installed) into the 1st inverter. The second inverter and wiring kit has a pre-made wiring harness that connects the second inverter into the PDP panel. For a DC coupled system, you would also need Charge Controllers. If one Sol Ark was enough, that would be great. With two of them, hooking everything together is going to be an issue. A bunch of connections will need to be made. For example the incoming generator wires have to Y into each inverter.

The Schneider system can easily expand to include additional inverters and charge controllers without all kinds of external wiring. It is actually a very slick system.

 

[anuccite]

I didn't fully read everyones reply... But let me add, with the well situation, you could go with a large storage tank, and "automate" the pump to fill your storage tank during the day, when your demand is lower and the sun is shining .. I think if you have the cleared ground space, and have a good southern exposure, you can make it work. The overnight / cloudy days will be the costly part because of batteries.... Can't wait to hear more about your decision / progress

 

[ksmithaz1]

For most solar systems, summer is not the time you come up short. Yes, the A/C runs a lot, but PV production is very high. I am consistently exporting power in the summer. It is winter when my system produces less than I consume. So during winter a hot water heater and electric drier really would be a significant portion of electricity use. Every time I do a load of laundry my KWHs per day spikes. Now you may be suggesting that @Themillpondhouse buy $60,000 of batteries rather than minimizing his electricity use by buying a $1000.00 drier. I think most people are looking to be a little more practical.

Yes, I know off grid people use propane. I just don't have a good estimate on the cost of generating a KHW of electricity from propane. I am quite certain it is less than $300.00.

​

I keep forgetting about the free propane that comes with the gas dryer. This is not about being efficient. Insulate, High seer HVAC systems, etc if your building. Dumb not to. Off-Grid, the solar infrastructure is CAPEX not OPEX. To me I'd want to pay up front and make my OPEX as low as possible. I want to be self-sufficient. The more batteries you buy the less you need to rely on a generator. You have to buy enough to get you past your average daily load +10% times the number of days of ZERO solar production you are willing to tolerate before relying on the genny. Get a gas stove and dryer, and you lower that load, but it won't get you out from under the gas bill. Pick your poison, at some point you rob Peter to pay Paul.

If your winter solar production is that abysmal and you can't overpanel to make up for it, then you need to decide if a few months of propane to run a generator making up for missing solar output to run an electric dryer/stove is more/less than running your dryer/stove on propane 12 months a year. Definitely a valid discussion.

You could have two stoves and two dryers, one of each. Swap them out with DST. You could probably get by with 120KWH ~ $25K of batteries, at the expense of fewer days of no solar thus a bit more propane to run the genny. Depending on what the boss is willing to tolerate, you don't have to do "optional" laundry during a full week of no sun. Again it does depend on where you live. If the folks here are to be believed, the abysmal period is ~11/1 until ~3/1, maybe 3-4 months. Even at that they report good days, weak days, and bad days for solar. I just don't think electric appliances are really going to beat you up that badly in the winter vs burning propane year round.

 

[Banjoman]

If you're going to be in a well, look for a solution that has a low surge. Like the grundfos pumps.

I wouldn't get Mr cool units. Get a regular mini split and a $120 vacuum pump and gauge kit. That way you can shorten the lines as needed

I sell Grundfos. They also make solar powered well pumps: https://product-selection.grundfos.com/us/products/sqflex?tab=explore

But I sell to heavy industrial/chemical users so no I cannot sell directly to you. Easy enough to find online though.

 

[Danke]

I have a grid tied system with full net metering. So for me, yes I do have an electric drier and I have no plans to replace it. Driers along with water heaters are energy pigs. Now your situation in Phoenix is better than mine. You are farther south and there are very few long periods of cloudy days. In Louisiana the situation is probably somewhere between us. Because this is a fully OFF GRID system, just pulling a few KWHs from the grid to dry a load of laundry is not an option. Putting off laundry for a week because it is cloudy may not be an option either. For someone trying to live a normal life in an off grid home, running out of power because you needed to do laundry really isn't an option either.

My situation is different. With full net metering I can push power to the GRID during the day and pull it back later for free. My batteries are there just to get me through power failures without extreme inconvenience. If we get a longer outage during the winter when my PV generation is consistently less than consumption, I will need to run a portable generator once or twice a day to top the batteries off. Yes pulling out and hooking up a portable generator is a pain, but this works for me. It is a situation I can live with if I have to in the event of a power failure at the worst possible time. I don't think this is acceptable for someone fully off grid.

For someone fully off grid and just looking for a feasible system, I think what makes the most sense is to design the system such that it can supply your house 95% of the days. Then supplement that with a generator about 15 days a year. Getting to that 95% is going to be significantly cheaper if the overall load on the system is less, so reducing overall consumption is part of the solution. This is especially true with batteries. I would make sure the system has plenty of KWs of inverter capacity, especially surge current if driving a well. For battery storage, I would make sure I had 1 day of storage for a winter day, and maybe a little more to make sure I can run A/C after we lose PV production in the evening. In summer you get better PV production and if it is cloudy A/C consumption also drops, so I wouldn't size this for one day of the highest energy use. Let's say we go with 30 KWHs of storage and that gets us through 95% of days without needing the generator. If you have sized the system to meet the power requirements 95% of the days, you will run the generator 15 days a year.

Now lets say that instead we double our storage to 60 KWH. That might cover us for 98% of the days. We would still need to run the generator about 6 days a year. So doubling storage will cost us about $9000 and save us from 9 days of generator use.

The cost of generating 1 KWH on a natural gas generator is about $0.20. The cost of storing 1 KWH in a battery is about $300.00. Yes the battery can be used more than once, but you won't break even until you have completed 1500 cycles. It will take you more than 150 years to recover the cost. My idea is to not pay more overall for a comfortable off grid life style.

Now if the system is undersized, the only down side is that the generator will run more than you planned. Based on experience, you could add either more solar or more storage depending on where the system is falling short. Adding more panels and possibly a charge controller or more batteries shouldn't be a big deal.

You can get an all-in-one washer/dryer heat pump unit. That would take less energy than a regular electric dryer. Also, you can still do some essential laundry on cloudy days if your wardrobe is minimal. Just hang the clothes up to dry.



Not as effective, but you can hang clothes up inside too.

 

[wheisenburg]

You can get an all-in-one washer/dryer heat pump unit. That would take less energy than a regular electric dryer.

These heat pump dryers are more efficient. They also cost twice as much and they are far more complex and hence more unreliable. The same can be said for heat pump hot water heaters. Also, for a family, it does mean that it will take at least twice as long to do each load of laundry since you can't have both the washer and dryer going at the same time.

You may save energy, but is it enough to make up for everything else?

 

[wheisenburg]

I keep forgetting about the free propane that comes with the gas dryer.

It's not free. If you double your batteries from 30 KWHs to 60 KWHs and use an electric Dryer you might reduce your generator days from 15 to 6. Instead you go with 30 KWHs and a gas dryer, so you save $9000 in batteries. Instead you will generate say 30 KWHs of additional electricity from the generator for 9 days each year. So 270 KWHs at .20 at KWH = $54.00 a year for the extra propane. The estimated annual cost to run a propane dryer is about $100. The combined cost of additional propane with my suggested configuration is $158.00. That means it will take you about 58 years to break even on the cost of your additional batteries. Most (not insane) people will look for a payback period of under 10 years to consider a project financially viable.

Do you think you could find any investors if you pitched them a project with a 58 year payback?

Now you are free to do what ever you want with your money, but if you are advising other people that they need 120 KWHs of batteries as a "Starter off grid system", you have some duty to know what the hell you are talking about.

 

[Madcodger]

I don't want to get into a battle with anyone, but I have to say that I think @wheisenburg is giving some great advice here. Keep the system size reasonable, and just plan for a reasonable amount of generator use from time to time. You're not gonna destroy the planet with occasional, overall-infrequent use.