Suggestions for whole house off-grid system?

timselectric said:

I personally would be looking at off grid AIO's for an off grid location.
Hybrid AIO's just add expense for unneeded features.

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Yeah I was thinking the same thing. The Midnite AIO coming soon would be worth a look.

ksmithaz1 said:

If you are building from scratch, to be "off-grid", I'd likely skip the pretty batteries, and grid tie inverters, lots more options these days. Till I'm blue in the face, what matters on your inverter front is your peak DEMAND. Multiple 6000XP, or look into some of the 10KW units showing up out there. I'd get a tall rack of RUiXU's (10x5KWH = 50KWH, $14K).

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I get it... I agree, I need to 100% focus on the demand aspect first then figure out everything else. Otherwise it's a big waste of time! I like the idea of using 3-4 6K XP's. They are stackable, meant for off grid use, and I am already familiar with them.

ksmithaz1 said:

Over-plumb an outbuilding, build it with room for extra inverters, and a couple of extra tall battery racks, maybe room for 4, plan on buying 2, maybe start with 1. Run 240A AC feed wiring back up to the house run a nice 200-240A panel with lots of breaker slots. (On the off chance you get a couple three EV's or something). All electric 2400sqft home, you will need around 100A as a minimum, High demand items: 5T-HVAC is 25A + HWH 20A + DRYER 20A + RANGE 30A = 95A), I'd shoot for 150A of inverter ~ 36KW, 30 (3x10) would probably work, leave room for one more, could start with 2 and see how it goes.

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Again, I need to back and figure out what the load will be before I can do anything else. No EV's, not a chance. We would be using a good propane powered combi unit for the heat and hot water (Viesman or Bosch). Dryer and fridge will be propane powered as well if at all possible. Everything else, well pump, all other appliances, and general house use (lights, outlets, tv, etc) would be powered by the panel. I love the idea of having a large panel too, plenty of room for expansion. Even if the demand is not there immediately, having the option down the road is really good.

ksmithaz1 said:

They make variable / multi-stage compressors for central air, expensive but do it right, it will reduce your current draw/spiking, or engineer for mini-splits as you see fit. Assuming you plan on heat-pumping, with propane backup for heating / generator, leave yourself room for the genny/venting, and figure out a nice big tank and the feed lines. I'd build it with block, minimum 10x12 or something, lay it out, inverter wall, then 4 racks 2ft wide 4 deep. I'm working on this now, I've already commited to the 18K's, at the time I wanted to make sure it would start my 4T-HVAC, they demo'd that on a video. I had lower end units that fell over I had to replace, annoying, but it's only money.

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I would like to have a good quality ducted mini split system to provide cooling only. (I have a lot of research to do on this still to see how it could be done on a timber frame house.) We will be installing radiant forced hot water heating systems on the first floor and baseboard heaters on the second floor.

At the end of the day, we want an efficient, comfortable, and off grid house in the woods. I am determined to do this at this point, now it's just a matter of when and how

JBoffgrid2022 said:

baseboard heaters on the second floor.

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Hot water not electric, correct?

JBoffgrid2022 said:

I would like to have a good quality ducted mini split system to provide cooling only. (I have a lot of research to do on this still to see how it could be done on a timber frame house.) We will be installing radiant forced hot water heating systems on the first floor and baseboard heaters on the second floor.

At the end of the day, we want an efficient, comfortable, and off grid house in the woods. I am determined to do this at this point, now it's just a matter of when and how

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I would not be so quick to dismiss the heat side. I've not seen a mini-split that does not heat as well, and they are getting to where they work down near absolute zero (well maybe not that low). I get the "gas heat, gas stove, gas, hwh, gas from beans, (er... too much blazing saddles)", but my problem with it is, now you have to buy gas. Now some of the folks here were talking propane at $0.50/gal. Ok then for now that's sort of a no-brainer, but personally I adore my induction cooktop, and despise gas ovens. If you can just build out your solar to handle it why buy gas? I'd probably build a ranch, not a 2-story and dig it in. You will probably do whatever your teenage bride likes . The in-floor / pex stuff is pretty good/efficient. Make sure you engineer multiple redundant loops with some bypass manifolds. They do sometimes fail, ( and floor cores suck ) and I'd look at a dual electric/gas heating system for it. Same thing for your HWH.

The thought crossed my mind you could put in both a tank for electric, and a gas demand hot water. Pass the electric heated water thru the demand system, put a sensor with a short delay and turn on the demand system if the electric is not pushing hot water. DIY dual setup. Lather, rinse repeat for the in-floor setup, if you can't find something that already does something similar. Of course, if you have the solar, it's bloody silly not to use it, but when it turns to sh*t, your gonna be using gas anyway, likely at some point to run a genny as well so. . .

Maybe split out to two panels a true "critical loads" panel for all the critical loads (Lighting, fridge, gas system controls, etc), and a high load panel for mini-splits, electric heating stuff, the EV you are not going to buy, whatever eats it up. The High load panel de-energizes with say 40% SOC on the batteries, depending on how agressive you get with battery purchases. The critical panel stays hot all the time, and the inverters turn on the generator as the SOC drops to 15% or something, let it charge the batteries to 30% and turn off (Below the high load cutoff) , keeping the lights on, and all the controls working. I think the EG4's also support generator assist now, so you you don't have to buy a ridiculous generator, just something that is a little beefier than your average usage on the critical panel. I think all that is doable with minimal fuss, and won't really break the checkbook either.

I hope it all goes well for you, be sure to keep us posted.

Quattrohead said:

Hot water not electric, correct?

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correct

ksmithaz1 said:

I would not be so quick to dismiss the heat side. I've not seen a mini-split that does not heat as well, and they are getting to where they work down near absolute zero (well maybe not that low). I get the "gas heat, gas stove, gas, hwh, gas from beans, (er... too much blazing saddles)", but my problem with it is, now you have to buy gas. Now some of the folks here were talking propane at $0.50/gal. Ok then for now that's sort of a no-brainer, but personally I adore my induction cooktop, and despise gas ovens. If you can just build out your solar to handle it why buy gas? I'd probably build a ranch, not a 2-story and dig it in. You will probably do whatever your teenage bride likes . The in-floor / pex stuff is pretty good/efficient. Make sure you engineer multiple redundant loops with some bypass manifolds. They do sometimes fail, ( and floor cores suck ) and I'd look at a dual electric/gas heating system for it. Same thing for your HWH.

The thought crossed my mind you could put in both a tank for electric, and a gas demand hot water. Pass the electric heated water thru the demand system, put a sensor with a short delay and turn on the demand system if the electric is not pushing hot water. DIY dual setup. Lather, rinse repeat for the in-floor setup, if you can't find something that already does something similar. Of course, if you have the solar, it's bloody silly not to use it, but when it turns to sh*t, your gonna be using gas anyway, likely at some point to run a genny as well so. . .

Maybe split out to two panels a true "critical loads" panel for all the critical loads (Lighting, fridge, gas system controls, etc), and a high load panel for mini-splits, electric heating stuff, the EV you are not going to buy, whatever eats it up. The High load panel de-energizes with say 40% SOC on the batteries, depending on how agressive you get with battery purchases. The critical panel stays hot all the time, and the inverters turn on the generator as the SOC drops to 15% or something, let it charge the batteries to 30% and turn off (Below the high load cutoff) , keeping the lights on, and all the controls working. I think the EG4's also support generator assist now, so you you don't have to buy a ridiculous generator, just something that is a little beefier than your average usage on the critical panel. I think all that is doable with minimal fuss, and won't really break the checkbook either.

I hope it all goes well for you, be sure to keep us posted.

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I love it, and really appreciate the in depth response and viewpoint. I'm a firm believer that there are more ways to skin a cat (or chicken, why the hell would we skin a cat? Gross.....). I have used gas stoves to cooking and will not budge on that one but I understand why people like them. No teenage bride here, just an amazing 35yo bride who is down for the ride!! (Way more useful than a teenager )

I will look into the redundant loops on the radiant flooring. We will have a good old fashioned wood stove as a back up heater. I'm also thinking of having dedicated panel/battery setup for a DC heat pump system instead of AC powered. Maybe it would use less energy thus eliminating some of the overall energy needs.

I appreciate your explanation of the loads but unfortunately I am very lost by it! I will need to spend some time when I'm not falling asleep and look it over in more detail.

I will keep this post updated as I make or break progress and thank you all again!! And yes, I am a very gassy son of a bitch! (My wife is asking me to sign a contract to not fart in the new house....Um, that's a no go honey)

JBoffgrid2022 said:

No teenage bride here, just an amazing 35yo bride who is down for the ride!! (Way more useful than a teenager )

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You should constantly remind her she is your lovely teenage bride, and looks just like she did at her prom (or some other appropriate photo of her as nubile young lady of youth).

For years i was never a SOL-ARK fan ... I always leaned toward the EG4 side of the house on the major things ... BUT recently we have been using these SOL-ARK 15s for the last 6 months and they have simply made all of our lives easier -- the system is bullet proof ... PLUS more importantly - or at least as important - is the customer service we are getting out of their guys in Dallas .... they have worked with us on getting our stuff up and running in some of the most austere and remote locations -- and when you call them -- THEY ANSWER - and their guys seem to know how to troubleshoot ... not trying to beat a dead horse but complete night and day difference between Signature Solar and them ... SOOOO if youre not married to EG4 stuff -- you might want to look at the SOL-ARK 15 stuff ...

We have ZERO relations with SolArk or any of their distributors .. BUT will have to say thanks to "Unplugged Texas" (YOUTUBE) and "Engineer 775" for making their YouTube videos so convincing that we tried out a system and never looked back ... being able to plug in 19,000W of panels into one single device makes our lives out here much easier ...

For batteries we just go the cheapest route -- right now our go to is either EEL or DOCAN .... at this point in the game its all starting to smooth out as to what everyone is offering and you just go with the lowest cost that you know has historical performance ...

I'd say we're trying to do something similar to you, @JBoffgrid2022 . Building a house (and a separate barn with guest quarters) in Maine this year, and very likely to keep it off grid because I'm tired of all the rapid on-off hammering of my equipment from CMP every time a branch somewhere taps a wire. At this point we've decided to go all-electric for everything except the radiant hydronic (in-slab) heat and possibly the dryer. We've had an induction cooktop in the past and my wife liked it even better than gas, so figuring that into the mix. House will have ~R40 walls and R60 ceiling, very tight,, so BTU requirement for heat will be well under 20 per SF.

For heating, I've convinced myself to go with a propane boiler with buffer tank to start, but keep the domestic hot water separate, primarily to simplify the system. I had a friend whose combi-boiler went down last year and it took the service guys forever to get parts. I figure I can always swap out the water heater quickly with a quick trip to a big box store, but that's not possible if it's tied to the heating system. When the price of air-water heat pumps comes down in a few years (a bet I'm making) I plan to put one in. That'll allow us to have both it and the propane as heat sources. For now, a couple of inexpensive air-air mini-splits will provide cooling and shoulder season heat, along with backup heating if the boiler goes down.

I built a 1300ishsqft offgrid semi-underground house in the woods.
It sounds like you are basing your usage on former homes. You don't like that life, that's why you want to move to the woods. Don't take that life with you or try to replicate it. You want peace, quiet, simplicity.
After designing the house and choosing appliances for efficiency, we average about 6kwh/day outside of summer ac usage. This also meant replacing the dryer with a carousel clothesline, which has worked great. Anyway, spend a lot of time with the energy audit before you buy anything. And have fun with it!

Madcodger said:

We've had an induction cooktop in the past and my wife liked it even better than gas, so figuring that into the mix.

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We're also fans of induction (the wind blew the gas flame around so much that the gas cooktop was unusable), pretty efficient in just heating the pan just the exact amount you need, but everyone has preferences. Plus a 20# propane fill is like $80, so we even use the sous vide for most grilling too.

wpns said:

Plus a 20# propane fill is like $80, so we even use the sous vide for most grilling too.

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I guess because you're on an island.
And it makes propane fueled generator much less attractive.

In the US, we can buy an already filled tank for $68 (think it was under $50 not long ago),
or exchange empty for full for $22

We use 3 of those propane tanks per month for ODHW and cooking. 2 Adults

ghostwriter66 said:

For years i was never a SOL-ARK fan ... I always leaned toward the EG4 side of the house on the major things ... BUT recently we have been using these SOL-ARK 15s for the last 6 months and they have simply made all of our lives easier -- the system is bullet proof ... PLUS more importantly - or at least as important - is the customer service we are getting out of their guys in Dallas .... they have worked with us on getting our stuff up and running in some of the most austere and remote locations -- and when you call them -- THEY ANSWER - and their guys seem to know how to troubleshoot ... not trying to beat a dead horse but complete night and day difference between Signature Solar and them ... SOOOO if youre not married to EG4 stuff -- you might want to look at the SOL-ARK 15 stuff ...

We have ZERO relations with SolArk or any of their distributors .. BUT will have to say thanks to "Unplugged Texas" (YOUTUBE) and "Engineer 775" for making their YouTube videos so convincing that we tried out a system and never looked back ... being able to plug in 19,000W of panels into one single device makes our lives out here much easier ...

For batteries we just go the cheapest route -- right now our go to is either EEL or DOCAN .... at this point in the game its all starting to smooth out as to what everyone is offering and you just go with the lowest cost that you know has historical performance ...

Click to expand...

I will look into SOL-ARK as an option. I have a budget for the project at $50k all in. We may end up never using that full amount (which would be amazing!) but I want to at least plan for that amount. I am partial to EG4, but not Sig. Solar due to the same issues most people have, shipment damage, customer service, etc. They have made a good attempt to help rectify my issues but in no way, shape, or fore have been helpful in the designing or technical assistance aspect. Quite honestly, I was very disappointed when I first attempted to get our camp setup with off grid power. Customer service referred me to their "design team". When I emailed them asking for their help on this, they replied that their company doesn't offer design services lol. Wowza. Anyway I appreciate your input!

Madcodger said:

I'd say we're trying to do something similar to you, @JBoffgrid2022 . Building a house (and a separate barn with guest quarters) in Maine this year, and very likely to keep it off grid because I'm tired of all the rapid on-off hammering of my equipment from CMP every time a branch somewhere taps a wire. At this point we've decided to go all-electric for everything except the radiant hydronic (in-slab) heat and possibly the dryer. We've had an induction cooktop in the past and my wife liked it even better than gas, so figuring that into the mix. House will have ~R40 walls and R60 ceiling, very tight,, so BTU requirement for heat will be well under 20 per SF.

For heating, I've convinced myself to go with a propane boiler with buffer tank to start, but keep the domestic hot water separate, primarily to simplify the system. I had a friend whose combi-boiler went down last year and it took the service guys forever to get parts. I figure I can always swap out the water heater quickly with a quick trip to a big box store, but that's not possible if it's tied to the heating system. When the price of air-water heat pumps comes down in a few years (a bet I'm making) I plan to put one in. That'll allow us to have both it and the propane as heat sources. For now, a couple of inexpensive air-air mini-splits will provide cooling and shoulder season heat, along with backup heating if the boiler goes down.

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Sounds like a fun project too! I'll keep you all update on my progress. I will also look into the differences between separating my furnace with the hot water heater. I like that option a lot considering my existing combi unit crapped the bed and now only functions as a furnace lol.

wpns said:

We're also fans of induction (the wind blew the gas flame around so much that the gas cooktop was unusable), pretty efficient in just heating the pan just the exact amount you need, but everyone has preferences. Plus a 20# propane fill is like $80, so we even use the sous vide for most grilling too.

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Yikes $80 for 20lbs? It’s $10 around here to refill 20lb tank.

NC_hydro said:

Yikes $80 for 20lbs? It’s $10 around here to refill 20lb tank.

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IKR? Even on the main island it's $20 for a 20# refill, but that's boat fuel and a rental car or taxi away.

If I was going offgrid I would go with a high voltage battery system rated for 410V. I did that with an EV years ago and it was amazing. I was pulling 40KW peak to the main traction inverter.

If you're in a 110V country, halve that and use two systems for split phase, or run everything 240 and use a center tapped transformer at the output of the inverter.

So that voltage gives you 128Cells and a voltage range of 380 to 440V.
At those voltages you need thin cable. You can use PV cable. You can use any solar panel voltage and boost it to give you that output (MPPT comes to mind). Since it's a boost converter you don't run the risk of the mosfet failing and dumping high voltage DC on your batteries.

You can run a generator with only a rectifier and boost converter to charge your batteries. I used two 1.5KW modules for my car, back in the day to charge from a 240V socket and they run inside the car without a Fan in all but the hottest weather (car interior can go 45+C in summer) PFC converters can be modified for this, by changing the output capacitor to 500V and they will run your generator efficiently, or if you have grid, you can charge from that at 96% efficiency. Because it's boosting, you can make your own MPPT. Your battery voltage is higher than rectified mains, so it doesn't draw power in case the converter fails.

Specialized DC fuses exist for solar arrays up to 1000V and you only need 20A-40A for a typical house instalation up to 15KW. The inverter will draw power straight from the battery bank, with zero conversion losses and very little standby power losses as there is no need for a transformer stage.

LG already uses 400V batteries for their AC coupled inverters. They too claim 96% roundtrip efficiency. You could look into using that if you don't want to build your own.

BMS needs to be custom made, I would not trust a mosfet to contain a failure at those voltages... having said that, I also don't trust them to contain a short circuit in a 48V pack... Instead, use them as a pilot signal to drive a high voltage DC contactor suitably fused and keep them in banks of 48V. You need 8 of those. Current can be measured anywhere in the circuit by a shunt. There are marine systems that run shunts for those calculations (They are reset when the battery is fully charged or discharged) so you only need to keep the individual cells balanced. As the contactor turns off the whole pack, the most a BMS will see is the voltage of it's own pack (~56V). There is never a situation where one opens and open circuit voltage is across its terminals!

In a 48V system above 5KW, the inneficiencies converting from solar panel to battery, back to 350V for the inverter are 75% at best and the ammount of current needed is very high, which is a real fire hazard. Then you also need large inneficient converters to charge the power source from grid or generator, which you most likelly will need in winter.

Also don't forget that the system needs to be maintained. Failed inverters or batteries, lightning, etc as well as aditional home insurance in case of a fire.

If your driving goal to go offgrid is to save on energy, run some maths too. Those systems are nice to have as a backup, but they are seldom more cost effective than using the grid. Grid tie systems, offer a good compromise, particularly if you can sell the excess in the summer.

hsync33 said:

If I was going offgrid I would go with a high voltage battery system rated for 410V. I did that with an EV years ago and it was amazing. I was pulling 40KW peak to the main traction inverter.

If you're in a 110V country, halve that and use two systems for split phase, or run everything 240 and use a center tapped transformer at the output of the inverter.

So that voltage gives you 128Cells and a voltage range of 380 to 440V.

LG already uses 400V batteries for their AC coupled inverters. They too claim 96% roundtrip efficiency. You could look into using that if you don't want to build your own.

BMS needs to be custom made...

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Do you have an HV battery inverter in mind, either for your 240V single phase or US 120/240V?

I've got Sunny Boy Storage, which uses LG RESU-10H battery (150V battery and DC/DC bidirectional boost converter to 400V), also BYD which is native ~ 200V to 400V depending on number of modules in series.

What I don't know is BMS for this HV inverter, or for StorEdge which takes a different version of the LG RESU-10H, or other HV battery inverters.
We obviously need a BMS which talks to the inverters; those aren't just given a voltage like 48V models can be.

Hedges said:

Do you have an HV battery inverter in mind, either for your 240V single phase or US 120/240V?https://www.aliexpress.us/item/3256805505130021.html

I've got Sunny Boy Storage, which uses LG RESU-10H battery (150V battery and DC/DC bidirectional boost converter to 400V), also BYD which is native ~ 200V to 400V depending on number of modules in series.

What I don't know is BMS for this HV inverter, or for StorEdge which takes a different version of the LG RESU-10H, or other HV battery inverters.
We obviously need a BMS which talks to the inverters; those aren't just given a voltage like 48V models can be.

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Normally there is little point in having the BMS communicating with the inverters, unless they also do charge and want to manage the cells, which an AC coupled or hybrid inverter will do. For Off grid - as long as everything is well they just draw as much as they need, just like a low voltage unit would do and I immagine being an offgrid system you'll have things like a backup in place long before the batteries are cutting out (unless you're looking into a managed solution, but those tend to be proprietary)

The BMS should have a simple on / off isolated drive signal to shuts down the inverter when something is not right, Ideally before opening the main battery pack disconnect switch. Programmable under / over voltage switches are also available for DC that can be fitted in a DIN Rail. I use some of these to terminate charging at 3.40V when using a charger set to a voltage of 3.65 per cell. They have a top limit of 400V, so you may need to use two. They have programmable hysterisys too.

Those could be options.
Some chinese inverters also take 400V directly - You can identify them by the ability to take a high voltage MPPT. They boost it to a final 400V bus and run an inverter stage and a battery charger from that.

You can go deeper and use some variation of these inverter modules. That's the barebones section that takes the HV and outputs a clear sine wave at 240V inside the inverter. They are available in larger outputs. I have used the 3KW variant to run inductive loads such as a 12000BTU air conditioner without problems, or a water heater from a DC supply, so I don't burn the thermostat contacts with DC. Idle current draw is about 5W including a small supply to the IGBT's. this one is an upgraded variant with a pre-charge and IGBT supply built-in to charge the DC caps when first connected.