Number crunching

Yep, EcoFlow is one of the battery-based backup generators I have looked at. BLUETTI is another brand I have checked. The YouTube video you linked says it is a 3.6kWh unit and the tandem link gets up to 7.2kWh. It is currently sold for a $5k price tag on Amazon with a Prime Day discount. (regular price $6,600). The price of the pack is quite high especially when it gets up to 10kWh size.

The biggest problem with it is that it stores only 7.2kWh of electric energy. That is good for only about ~17 hours of operation in our home during power outages. If we use it like grid-supplied electricity, it lasts only ~6 hours. After that, the battery is depleted. Unless it is hooked up with solar PV and sunshine or other external electricity sources, after a single day of use, it is of no use. So, in case of an outage lasting for several days, I can't rely on it. And even with a solar panel connection, there is no guarantee that sunshine is going to generate enough electricity to replenish the battery pack for prolonged power outages.

As a system for a very short duration of power outage or low load operation just for lights and a few appliances, it is convenient, but, it is not for multiple days of high power output operation without some type of other electric sources. And it certainly is not a permanent off-grid power source.

 

It is a niche product.

For serious long term off grid electric generation - as one gentleman mentioned when he bought up new products- Generac makes a generator now for off grid applications and sells battery modules to go with it.

Generac Power Systems - 15kW EcoGen Home Generator - 7163

"Whether the off-grid lifestyle is a choice or a necessity, you are responsible for producing the energy you consume – even when there’s no sun or wind. Ensure you never have dead batteries with the Generac EcoGen–the only automatic standby generator designed and warrantied specifically for off-grid use with an alternative energy system."

Generac Power Systems - PWRcell

"The PWRcell system is not just a powerful battery, but is also the most flexible and scalable home energy system on the market"

The price a fellow is willing to pay is the only limiting factor.

 

But the Generac generator and battery PWR cells are just as niche products as the EcoFlow. For the Generac generator to work continuously, it has to be connected to the city gas line. I have never investigated how long it runs on propane, but if it has to be refilled every few days, then I would not call it a permanent off-grid solution. Besides, it negates my goal of no fossil fuel dependence, since the PWRcells by itself will not solve the problem.

Yes, you are quite correct. That's why I have not pulled the trigger yet... or never. The rudimentary portable gas generator backup system I have now works fine for our couple of days of power outage. Despite the cost of running it ~$100/day... is still cheaper than almost any alternatives out there. But, I'm still investigating solar panels with backup battery storage to be used for the daily operation of some appliances in a small off-grid workshop (not for the whole house). If I can get a system up and run the entire 20A circuit of our garage (lights, garage door opener, occasional use of power tools, continuous running of the full-size freezer, and charging our car) for a fraction of the cost of the whole-house setup, then it may be worth the cost.

 

If I omit PHEV charging, I am pretty sure I can get an entire kit for much less than $6K. For example, this kit will be perfectly fine for running a small off-grid workshop running just lights and a few appliances, I think.
https://shopsolarkits.com/collections/off-grid-solar-kits/products/complete-off-grid-solar-system-ultimate-backup

Yeah, as I understand, off-grid solar with a battery to charge a PHEV is likely to be a pipe dream. All the systems I have seen that use the solar generator to allow EV charging are grid-integrated and can get quite expensive. For examples: 8kW EV Solar+Battery Charging System Supports - LG Home 8 ESS with LG Smart Energy Box Kit | NAZ Solar Electric

 

If 2.4kWh is not enough, then you can go with 5.6kWh LiPo for $800 more @$4600 still less than your quote.
https://shopsolarkits.com/collections/off-grid-solar-kits/products/complete-off-grid-solar-system-ultimate-backup?variant=40337471996044

And, if you don't need a 240v inverter, then 5.12kWh LiPo can be less at $3,500.
https://shopsolarkits.com/collections/off-grid-solar-kits/products/complete-all-in-one-solar-kit-mpp-lv2424-2-400w-120v-24vdc-800-watts-solar-pv-hbk-2?variant=41613331595404

If this is only for a small shop not being occupied all day, then I suspect a 5kWh battery would be an overkill.

Yeah, off-grid + EV probably doesn't exist. For me, if grid-tied solar is the choice, then using an EV as a backup battery as in V2H is even more attractive than a Powerwall.
GM says all of its EVs will be able to power your home by 2026 - The Verge

 

FAQ from the linked page says following:
Can I use a generator or the grid to charge my battery bank if needed?
Absolutely. Your inverter comes ready to go with an AC input where you can hook up a stand by generator for charging the batteries on cloudy days or at night if needed. You can also use the grid as the AC input source if it's available.

 

I briefly looked at solar back up sans battery. Thinking in the event of multiday outage of being able to run the fridge and gas heaters at least part of the time. Between the additional cost, and variability in the system output, it just wasn't worth it without a battery.

A question is there any fuel savings to running the generator at a steady load to charge up the battery from time to time vs running the generator at variable load to run things? I do concede it likely won't be enough to be economical outside of regular power outages.

The Generac system isn't marketed for off grid systems. It's main residential market is standby emergency power. The battery is to allow more efficient use of genny fuel, and to allow TOU cost shifting. It might even be possible to have the generator turn on automatically when using it would be cheaper than the grid. Though very likely those considering it are also have or considering solar.

The other market, which might be more commercial, is for areas where the natural gas supply is more reliable or cheaper than the electric. This is a case in parts of Japan, and Honda has a true Atkinson cycle stationary generator. In this case, units that are cogen heat and electric are also available.

 

I don't run our generator like I drive a car, so I don't know how to run it efficiently. Ours is rated 6000W continuous/7500W serge portable dual fuel generator. On gasoline, it is rated to run 9 hours on a full tank (6gal) at 50% load. My experience has been that it runs ~8 hours on average on a full tank for our usage, but I am not exactly sure how much load. I don't know the total cost difference in fuel used by the generator if it is used to charge the battery at a constant load as compared to using it at a variable load directly. I am with you that even if the battery cost is excluded, I don't think there will be any fuel-saving. But one use case would be to use a generator during the day to charge the battery and run the house with the battery during night with a much lower load but still having electricity to keep the refrigerator and some lights. That will keep us rested at night. The generator is just so loud it keeps us awake if it has to run all night. During multiple days of power outages, we usually shut down the generator before going to sleep, but that means no lights, no water, no heater, and no refrigerator/freezer during the night.

I thought about using propane for the generator to run it continuously for a longer period. But that means I would have to have the propane delivered to the tank on a regular basis. We used to have a leased tank outside a 200gal size ? but since we almost never used our two propane heaters, the tank did not get filled for a long time... and one day, the fuel company just took the tank.

Sure, but the Generac link posted does sound like it is designed to be used off-grid.

ECOGEN 15KW GENERATOR FEATURES AND BENEFITS
Whether the off-grid lifestyle is a choice or a necessity, you are responsible for producing the energy you consume – even when there’s no sun or wind. Ensure you never have dead batteries with the Generac EcoGen–the only automatic standby generator designed and warrantied specifically for off-grid use with an alternative energy system.​

But in any case, in our situation without a propane tank on site, using it continuously is not possible, on or off the grid.

 

Meant to say this in my post, but then forgot. Going off grid requires solar or wind. The generator is still just a back up. Going off grid doesn't require one, it just might make designing the overall system more practical. My belief was just that off grid systems aren't the majority of sales.

Not sure what technical difference that would be needed between a generator designed for use with the grid and without. I suspect it is just in the paper of the warranty.

 

Keep us informed of the savings - it will be interesting.

We are interested in installing a solar system but at our age we would never see a payback - very hard to justify the expense.

We are looking at permanently installed home generator to run during power outages hooked up to our homes Utility supplied natural gas line.
What a huge difference in performance for certain brands. Right now, it looks like a Champion 14,000 Kwh dedicated Home Standby Generator with a 200 amp ATS is what we will go with. This unit runs at 62dB and uses only half the natural gas/hour of most of its competitors. It comes standard with a 10 year warranty.

If we were younger a Solar System would make more sense.

 

When we were younger the Solar System did make more sense. Now it's dwarf planets all over the place.