Advice on installing large off grid system.

Due to PGE hiking rates every quarter, being outrageously expensive to install(responsibility is all on the owner and hard to deal with I've decided to go off grid. Its a new build and as part of the required building codes in CA a 5.6kw enphase panel system was installed on a south facing roof. My loads will be high as it'll be a gentleman's farm with orchards, gardens, pasture. So the well and booster pump will be operating quite a bit from April-Nov (Plus I have 4 small energy whores {children} and 2 small 300 sqft guest units) Peak sun hours in Jan 3.34-Aug 7.43. My heaviest loads will be in summer with irrigation and A/C as it gets 110 degrees here. I'm going to estimate peak months loads of 3000kwh which would be a 22kw solar panel set up. I looked at local installers and one wanted to use 2 sol-ark 15's, (5) 14.3kw EG4 powerwall batteries, a kohler 20kw propane generator, an additional 17.3 kw solar array of Q-cell DUO BFG 480w. The cost was astronomical so I was looking at doing most of the mounting and laying wire myself and having an electrician do the wiring connections.
I was going to down size the array to 11-14kw and see how that goes initially and adjust lifestyle workflow. They mentioned having multiple orientations to catch the morning sun and then due south then southwest during the hottest time of day when the A/C is running. We will have mini-splits and 2 ducted systems. The panels will be on sinclair ground mounts. was thinking 12x400w canadian solar panels facing SE and 24x400w canadian solar panels facing SW. One sol-ark would be receiving the 3 strings of 8 panels each running 200ft on 8awg wire. The other sol-ark would be receiving the enphase panels (needs an ac coupler?can someone link a resource?) and the other 12 panels. The battery set-up is tight in the garage to keep it out of the impact zone but went with the EG4 powerwalls due to being code compliant in CA with UL 9540. I know diesel would be a better option for a generator but for now i'll already be having a propane tank so will stick with the Kohler 20kw for now.
Suggestions? Thoughts? Ideas?
Also tricks on mounting those 300lb batteries?

Here is my 2 cents.

This is a lot to unwrap.

Leveraging your “guesstimate” numbers

3,000 kWh / month equates to 100 kWh / day and 4 kW / hr

Double the that to 8 kW / hr to account usage during the day

Double it again for inductive loads 16 kw / hr

Add 50% so you don’t run inverters at full capacity 24 kw / hr

Looks like 2 Solark 15k appears to be a good estimate for inverter.


The battery bank size will depends on many factors. My personal and quick estimate is 2x times your daily usage so 200kwh. Restated, you have a two day buffer in a worst case scenario.

For my own personal system, I have a 5x battery bank to daily usage (10 - 20 kWh, varies based on time of year and my OCD).

For PV array size, again too many variables. Using worst case of 3 Solar hours, I would say minimum 30kwh array. For my own personal system, I have 10kw array.

I don’t know how much your quote was. Please share as we are all curious

Here is a quick diy break down from memory. These are not current prices.

2 Solar 15k = $12,000
0.30 / watt x 30kw PV = $9,000
$250 / kWh x 200 kWh battery = $50,000
Hardware, wiring, misc 25% of above = $18,000

Wild a$$ guesstimate = $100,000 plus a ton of elbow grease


Hopefully that gives you some perspective. There are too many unknown variables and you appear very new to Solar. This is a huge undertaking considering an estimate of 100kwh per day.

Dinobot248 said:

Double it again for inductive loads 16 kw / hr

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This doesn’t make sense.

What house is 100% inductive load on average? What inductive loads are going to be this big, continuous, and without power factor correction?

I think upsizing for surge is already enough to drop the duty cycle of the inverter.

Not that going down from two big inverters is possible. They are off grid so going from one to zero is pain

Also kudos for having the patience to reply to a wall of text with no vertical white space

As stated earlier, this is a wild a$$ guess with little to no tangible information.

The start of the calculation is 3000kw / month which equates to an average 4 kw / hour. Using this info, I am trying to size the inverter.

This is my opinion and estimation. Enough said !!

If budget is wide open, I would consider better gear. The generator long term is a pricey situation.

If budget is small, then thats a whole other conversation.

Dinobot248 said:

Here is my 2 cents.

This is a lot to unwrap.

Leveraging your “guesstimate” numbers

3,000 kWh / month equates to 100 kWh / day and 4 kW / hr

Double the that to 8 kW / hr to account usage during the day

Double it again for inductive loads 16 kw / hr

Add 50% so you don’t run inverters at full capacity 24 kw / hr

Looks like 2 Solark 15k appears to be a good estimate for inverter.


The battery bank size will depends on many factors. My personal and quick estimate is 2x times your daily usage so 200kwh. Restated, you have a two day buffer in a worst case scenario.

For my own personal system, I have a 5x battery bank to daily usage (10 - 20 kWh, varies based on time of year and my OCD).

For PV array size, again too many variables. Using worst case of 3 Solar hours, I would say minimum 30kwh array. For my own personal system, I have 10kw array.

I don’t know how much your quote was. Please share as we are all curious

Here is a quick diy break down from memory. These are not current prices.

2 Solar 15k = $12,000
0.30 / watt x 30kw PV = $9,000
$250 / kWh x 200 kWh battery = $50,000
Hardware, wiring, misc 25% of above = $18,000

Wild a$$ guesstimate = $100,000 plus a ton of elbow grease


Hopefully that gives you some perspective. There are too many unknown variables and you appear very new to Solar. This is a huge undertaking considering an estimate of 100kwh per day.

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Quote was 160K with a 30K discount not counting solar credit

sunsurfer said:

If budget is wide open, I would consider better gear. The generator long term is a pricey situation.

If budget is small, then thats a whole other conversation.

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Im trying to keep total cost around 80k including paying the electrician, so maybe 65-70K of material and a lot of elbow grease

sunsurfer said:

If budget is wide open, I would consider better gear. The generator long term is a pricey situation.

If budget is small, then thats a whole other conversation.

Click to expand...

Thanks for responding, what kind of gear do you have in mind? It would have to be CA code compliant which limits options, especially when county inspectors will be evaluating before occupancy.

Make sure you use a Grundfos well pump which does not have any power surge. To give you some idea, I installed a 14.4kW array last year using those exact panels (QCELL) along with a Sinclair ground mount system for them and total for the array, mount, and cement was well under $20k. FYI, those Canadian solar panels are made in China whereas the QCELLS are a South Korean based company working to make 100% of the panel within North America.

mp80 said:

Thanks for responding, what kind of gear do you have in mind?

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I would keep an eye on THE ONE.

Consider a stand alone system for your irrigation needs. I think if that is out of the equation you could downsize the house system and batterystorage, in turn saving you money.

Not sure if California is code exempt for agriculture, meaning no inspection or permit for irrigation = save money again. Worth checking into.

Also consider a diesel generator, more efficient for large loads and youll probably already have diesel at your farm. Look for continuous rated units not standby rated. The difference can be 30,000 hours vs 2000.

Sol-ark is good equipment with TX based support. And yes Midnite just came out with an attractive AIO to compete in that market. Referenced above in @rhino post as "The One".

If the sol-arks are in parallel, it mostly looks like one big system (doesn't matter what is plugged into what).

Enphase goes into the gen input /Smart Load connection. That way the sol-ark can disconnect in a grid down, excess production situation. Consider rewire as DC pv into the sol-ark.

You can get by with a smaller generator. Daily kwh divided by 8hrs should work. Runs continuously for 8 hours to provide enough power for 1 day.

If enphase goes into the gen port, or you have a generator larger than 19.2kw, then it needs to come in the grid input. You will then need a transfer switch. But you may want one anyway to make it easy to take the SA offline for service.

Look at RPS solar for your well pumps. They are based in Woodland Ca. They have a variety of different systems. Great product and I have been happy with their customer service.

Yosemite Fred said:

Look at RPS solar for your well pumps. They are based in Woodland Ca. They have a variety of different systems. Great product and I have been happy with their customer service.

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I really wanted to go with them, but the pump installer steered me away when stating the need to have two solar setups vs one. But rethinking it in the long term as hopefully further infrastructure will be next to the well pump (900ft from the house).

rhino said:

Make sure you use a Grundfos well pump which does not have any power surge. To give you some idea, I installed a 14.4kW array last year using those exact panels (QCELL) along with a Sinclair ground mount system for them and total for the array, mount, and cement was well under $20k. FYI, those Canadian solar panels are made in China whereas the QCELLS are a South Korean based company working to make 100% of the panel within North America.

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Yes I have the groundfos HSC20. How do you like the sinclair system?

That is a huge undertaking!
I'd start by taking a serious look for opportunities for downsizing and conservation. Every watt saved is a watt you don't have to produce.
Is selling off your kids legal in California?

East West orientations are mostly overrated for off grid. West can help for an undersized hybrid system when there are TOU rates involved, to take a bite out of the right part of the apple.

For off grid, if you manage to meet your winter loads you're pretty much going to be swimming in power in the summer no matter what. So design the system for winter, and in winter you're going to want south facing, maybe southwest if you have a cloudy morning sunny afternoon weather pattern.

Do lots of work in PV Watts, focusing on the winter production specifically.

mp80 said:

The other sol-ark would be receiving the enphase panels (needs an ac coupler?can someone link a resource?)

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SolArk has AC coupling built in. It’s a feature of inverters.

Enphase and saving money aren’t what I would put in the same sentence. Look into 2 or 4 port microinverters (if you are considering Enphase for a small sub array) or Growatt hybrid/grid tie string inverter (if it is a big array and it was recommended to you due to reasons of bad contractor). If it is ground mount then you don’t need rapid shutdown (saves even more on the string).

What was the cost for grid connection? To compare with hybrid and ESS costs assuming it’s not rejected out of spite to PG&E. Also a lot of people here UNDERVALUE the ongoing maintenance and up front design overhead (which may involve multiple iterations to eliminate bad stuff from messing up requirements design or implementation) of being your own power company.

mp80 said:

Quote was 160K with a 30K discount not counting solar credit

Im trying to keep total cost around 80k including paying the electrician, so maybe 65-70K of material and a lot of elbow grease

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How are you plan on doing heat and backup heat?

rhino said:

I would keep an eye on THE ONE.

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That looks great from a good company but I’d like to see it out in use for a year where every conceivable circumstance has had time work the bugs out. Kinda like not buying a first year model car. But yeah that inverter looks sweet.

Skypower said:

That looks great from a good company but I’d like to see it out in use for a year where every conceivable circumstance has had time work the bugs out. Kinda like not buying a first year model car. But yeah that inverter looks sweet.

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I'm excited about it too, but I bet they will oof on state specific regulations like 18kpv is with some POCOs being really nasty about PCS certification. Or, maybe MidNite will not have a workflow ready for the states that need export limiter lock paperwork.

(Export limiter lock, EG4 has figured out, unfortunately every time they're tagged about PCS they think we're asking about export limiter. LeSigh. Presumably SolArk has ironed out all these processes)