48v Off Grid Blueprint for Northern Cal?

[jerander]

Hello All,

I'm a general contractor in northern California and recently purchased some land in Sonoma county. We are in the process of developing the 5 sunny acres and are choosing to go off grid, although there is the option to tie into the grid but would require spending some money to add a pole since the run to the closest pole is about 250 feet away from our proposed building site.

I have some experience working with low voltage systems but have no solar experience and am looking for some assistance in coming up with a build. Presently there is only one ADU (guesthouse) on the property currently and we have not yet built the permanent home therefore I have no historic consumption data to help determine our estimated loads. We are on well/septic so we have the loads for the pumps and our plan is to build a 3BR home with a pool in addition to the existing guesthouse.

We are also in the process of permitting a pole barn and I was planning on mounting the PV array on the roof of the bar with a true southern exposure. We have plenty of places where we could also put a ground mounted array with full sunlight. We are weighing the pros and cons of putting the array on the roof since it's a light gauge metal building and we don't want to have to reinforce it to support the potential weight of the array.

I'm done lots of internet research and have heard many different ideas about the best bang for your buck. I have watched tons of the Will Prowse videos and am drawn to the idea of doing a 48v system perhaps with the Growatt 48V SPF 12kW DVM MPV 250VDC. I like the idea of a hybrid inverter but I also don't want to buy into a "combo" system which will potentially limit expandability. I thought I would buy a couple of the Sig Solar EG4 48v 100AH LiKEPower4 Batteries to start which would give me 200 amp hours of storage. Does this seem like a sound idea?

I would love suggestions for PV panels as well as I am sure there are lots of budget options out there. I should point out that we have an autostart 4000 watt generator which we can tie into the system for backup and we are planning to purchase an electric vehicle in 2023 so we know that we will have these demands in the future. The house construction is probably not starting until later this year and my wife who is an architect is designing the building with high efficiency standards in mind. While we don't have the specific electrical demands yet, we can safely assume that we will be incorporating electric powered radiant floor heating and on demand electric water heating, basically no gas powered or geothermal powered anything.

If anyone has suggestions or has done something similar with success we would love to hear about how you put the system together. I'm highly proficient with wiring and plan to do the install and setup myself with my crew of labor. Thanks in advance for any and all suggestions!

​

 

[timselectric]

On demand electric water heating is going to require a very large amount of inverter, by itself. Better off with a high efficiency heat pump water heater. And, you can size it for domestic hot water and in floor heating.

You can also dump excess pv output into a preheating tank.

 

[Hedges]

PV panels - check Santan Solar for (mostly) used panels, which can be a great bargain.
Read up on reliability of various brands. There are a number of failure mechanisms.

Having SE and SW facing PV arrays will flatten power production during the day vs. due South only.

Do you want a "value" brand, most bang for the buck? Or more expensive highly reliable hardware?
I use SMA Sunny Island & Sunny Boy. Some people use Schneider/Trace. Some use Vicron (which may or may not have any UL listed models.) Outback. Midnight.

Generator can mean not as big a battery needed. Batteries cost $0.25 to $0.50/kWh by the time they wear out from cycling (more expensive if they die of old age or malfunction before cycle life reached.) I prefer more PV, less battery, so system meets needs in times of less sun.

200 Ah at 48V sounds like a start, but you have to be efficient. My 400 Ah AGM, at 70% DoD for 280 Ah, can only make it through one night with inefficient appliances if I turn of things like yard lights. The goal should be to use power when it is made by PV, use batteries for minimal loads at night and starting surge of motors.

My system is grid-backup, not off-grid, so different need for battery capacity and lifespan.

Charging an EV with surplus PV would be nice, ideally vary charge rate according to production (don't think that is an off-the-shelf product.)
If you drive to work in the day and charge at night, that would mean storing PV power in one battery to charge another, less economical.
In that case, better to have use of a charger at the office.

 

[rcrracer]

A bit off topic. If you are adverse to paying property taxes, and because you own 5 or more acres, investigate building an agricultural building. Ag buildings can't have power, plumbing, or HVAC. Build all that on a trailer((s) that can be temporarily(?) parked inside the ag buildings. Mini split compressor on the tongue of the trailer to remain outside the insulated ag building. Don't advertise what you are doing. Nopermit required for ag building. There are setback rules. Batteries on trailer charged down at a temp pole down by the street?

 

[jerander]

A bit off topic. If you are adverse to paying property taxes, and because you own 5 or more acres, investigate building an agricultural building. Ag buildings can't have power, plumbing, or HVAC. Build all that on a trailer((s) that can be temporarily(?) parked inside the ag buildings. Mini split compressor on the tongue of the trailer to remain outside the insulated ag building. Don't advertise what you are doing. Nopermit required for ag building. There are setback rules. Batteries on trailer charged down at a temp pole down by the street?

Unfortunately we are just under 5 acres. We considered this when going through the permitting process. We even considered getting a variance for an AG building but we are 4.6 acres and not "close" enough to 5 acres to get a variance. We are permitting the barn as a garage which has a 16' height limitation.

 

[jerander]

PV panels - check Santan Solar for (mostly) used panels, which can be a great bargain.
Read up on reliability of various brands. There are a number of failure mechanisms.

Having SE and SW facing PV arrays will flatten power production during the day vs. due South only.

Do you want a "value" brand, most bang for the buck? Or more expensive highly reliable hardware?
I use SMA Sunny Island & Sunny Boy. Some people use Schneider/Trace. Some use Vicron (which may or may not have any UL listed models.) Outback. Midnight.

Generator can mean not as big a battery needed. Batteries cost $0.25 to $0.50/kWh by the time they wear out from cycling (more expensive if they die of old age or malfunction before cycle life reached.) I prefer more PV, less battery, so system meets needs in times of less sun.

200 Ah at 48V sounds like a start, but you have to be efficient. My 400 Ah AGM, at 70% DoD for 280 Ah, can only make it through one night with inefficient appliances if I turn of things like yard lights. The goal should be to use power when it is made by PV, use batteries for minimal loads at night and starting surge of motors.

My system is grid-backup, not off-grid, so different need for battery capacity and lifespan.

Charging an EV with surplus PV would be nice, ideally vary charge rate according to production (don't think that is an off-the-shelf product.)
If you drive to work in the day and charge at night, that would mean storing PV power in one battery to charge another, less economical.
In that case, better to have use of a charger at the office.

We are ultimately looking for good value (price) per watt. We would like to design a system with few parts which would likely mean less points of failure which is why a combo system seemed ideal and less pricey. Do you have anything negative thing against the Growatt or Sig Solar batteries? I know people are brand loyal over time, but since we have no experience with particular brands, we are looking for advice from others. Went through the same exercise before we bought our tractor. Some people told us to buy a John Deere, others said Kubota. We ultimately picked Kubota based on comments and advice from other people in our area.

 

[jerander]

On demand electric water heating is going to require a very large amount of inverter, by itself. Better off with a high efficiency heat pump water heater. And, you can size it for domestic hot water and in floor heating.

You can also dump excess pv output into a preheating tank.

That's very sage advice. I didn't consider the surge needed to heat on demand water and your idea of dumping excess into a preheating tank could also go to heating the pool I presume. Will definitely think to incorporate this into the design for the home heating/water heating.

 

[offgriddave]

I would go with Kubota as well. Now here's a question, Milwaukee or Dewalt?

I would go with MPP Solar hybrid inverter, a 5.1kw battery with 10 year warranty x per 500ft-750 living space, San Tan 350-400w panels

Absolutely no electrical kitchen, hot water, hair drier, mig welder anything. Propane on demand hot water, propane heat. French press for the coffee. Wood stove (or Liberty Rocket Stove) for heat.

There's a gentleman that posts on here the first thing you need to do is do an Energy Audit. I was able to get my consumption down to currently 100-200 watts per hour. That's crock pot, starlink internet (but 4g/lte/5g internet base station would also works), desktop computer (super efficent AMD 35w), 46" 4k tv , all my lights, coffee grinder, and 2x dewalt 4 bay chargers when I need to charge my 12+ batteries.

 

[jerander]

Hahaha...I've been a Dewalt guy for 20+ years. But with that said, I'm cheap so I get a lot of stuff from Harbor Freight as well

Do you have some specific equipment (brand/model) that you recommend that I consider?

While we are planning to live off grid, my wife is not about go completely without creature comforts. I can say for certain that there is NO WAY we could get down to 200 watts per hour. My son's gaming rig draws more than that I'm sure!

I'm also planning to run the business from the property so I will have some additional electrical overhead from the office. Because we are not there full time presently, we can audit our use. I should say, I'm not against spending money to get enough capacity to fit our needs, I just want to make sure putting together a system which delivers a good ROI, meaning best cost per watt of power produced and stored.

 

[timselectric]

I recently installed a Growatt SPF-5000-ES with an auto transformer. 6k worth of used Santan Solar cells and the Signature Solar battery.
I couldn't be happier, and I'm planning on expanding everything.

 

[jerander]

I recently installed a Growatt SPF-5000-ES with an auto transformer. 6k worth of used Santan Solar cells and the Signature Solar battery.
I couldn't be happier, and I'm planning on expanding everything.

Do you have a parts list or schematic that you followed? Which and how many panels did you purchase and how much PV are you producing and storing? Thanks!

 

[timselectric]

Currently driving, I'll get back to you later.

 

[offgriddave]

While we are planning to live off grid, my wife is not about go completely without creature comforts. I can say for certain that there is NO WAY we could get down to 200 watts per hour. My son's gaming rig draws more than that I'm sure!

I'm also planning to run the business from the property so I will have some additional electrical overhead from the office. Because we are not there full time presently, we can audit our use. I should say, I'm not against spending money to get enough capacity to fit our needs, I just want to make sure putting together a system which delivers a good ROI, meaning best cost per watt of power produced and stored.

this sounds like you're going to need a 40kwh-80kwh battery setup. Without an energy audit, I am not sure. But this is a bigger system. There are some incredibly smart people here who have these size systems and post a lot, you should search around. I'm not knowledgeable as my system and needs are under 5kwh at the moment

It was kind of risky of me to suggest a specific brand for hybrid inverter (MPP vs Growatt) Ultimately I did not go with growatt because of some weird issues I keep seeing popping up, but they are really popular and used here. Other brands, such as Victron and other high end systems are also used here. Basically with DIY, absent of incredible amount of research and good advice, you'll end up taking risks with a bunch of systems, that evolve. I have a MPP 5048, but I use a Victron Phoenix 375A.

Because your needs seem a little bit more enterprise-y (40kwh of batteries at $1700 shipped per 5kwh is $14,000), your budget is going to be pretty high. I would consider several hundred hours of research here or hiring a consultant. And again Energy Audit.

Can you sell you son's gaming rig and get him a ruger 10/22, tell him to go outside until his knees are skinned. It will save you $10k in batteries.

 

[timselectric]

I just remembered that you said that you were building a new house. This inverter isn't UL listed. Depending on your inspector, this could be an issue.
This is a link to Santan Solar. They have great prices and service.

SanTan Solar | One Stop Shop for DIY Solar Panel Needs

store.santansolar.com

I purchased 6kw of panels for under $2k.

 

[timselectric]

My current setup.

 

[Hedges]

We are ultimately looking for good value (price) per watt. We would like to design a system with few parts which would likely mean less points of failure which is why a combo system seemed ideal and less pricey. Do you have anything negative thing against the Growatt or Sig Solar batteries? I know people are brand loyal over time, but since we have no experience with particular brands, we are looking for advice from others. Went through the same exercise before we bought our tractor. Some people told us to buy a John Deere, others said Kubota. We ultimately picked Kubota based on comments and advice from other people in our area.

An all-in-one also means if anything fails, the whole system may be down. Getting a stackable unit and installing two would give redundancy.

I don't personally have experience with any lithium batteries outside of tools/cell phones/laptops.
18 months ago, I considered LG RESU lithium and SunXtender AGM (both $0.50/kWh of cycle life) and selected AGM based on cost and only expecting a couple hundred cycles , for my grid-backup application.
Some people using FLA Forklift batteries or Rolls Surette report getting 20 years out out them.

I think lithium may be a good deal if cycled to end of life. But sized for 3 days autonomy, they may age-out before that happens.
People here do have good experience with some lithium batteries, so a quality one might do well for you.
DIY LiFePO4 looks like it can be $0.05/kWh over its expected lifetime, so quite compelling.
A life test of dozens of batteries only had about 5% of brands complete the test, so quality/durability varies.

A few customers having precharge issues using SS battery with certain inverters:

Schneider xw pro 6848 not powering up with eg4 lithium battery

EDIT: CABLE IS DIFFERENT UPON EXAMINATION OF BOTH CABLES. MY MISTAKE. Last Friday, Signature Solar overnighted me a "programming cable". I assumed it must be different than the cable i already had that came with my batteries. I wish Richard would have asked me before sending as I already have...

diysolarforum.com

SMA, which I suggested, is quite expensive retail. There are still some new in the box liquidation sale Sunny Island units due to a company's bankruptcy. Since you're off-grid you don't need a GT inverter with the latest features required for grid connection. You may find old models for a bargain. An entire system still wouldn't be cheap (the 75% off list Sunny Island bargains are gone), but system might be 50% off.

You need to decide what you have to start. Induction motors draw locked rotor amps, about 5x running amps. Alternatives include VFD, which is built into Grundfos well pumps. Some inverters have decent surge output, e.g. Sunny Island 11 kW for 3 seconds. Schneider and others do too. Some of the lightweight HV inverters do. Midnight has their "DIY" line of rebranded inverters, and an in-house design called "Rosie the Inverter". Some examples of those starting induction motors like a well pump, but I pointed out that their demo of starting four air compressors simultaneously was brush-type motors.