bimodal inverter w solar microinverters

[SunEagle]

I have a couple quotes (and googling for average costs confirm) that installing a generator for backup power is not cheaper. At best, it's the same cost as far as I can tell. And ofcourse, generators are not without their own maintenance requirements.

Really. How much is it going to cost for a battery system and how many kWh will it produce in it's lifetime?

Now compare that cost / kWh and tell me that a propane generator will cost more to produce the same kWh over the same length of time.

IMO FAT CHANCE the battery system will be cheaper.

[kevincw01]

from a lifetime or TCO perspective you might be right, I haven't done that math. Not sure what the lifetime of a generator is TBH. But up front costs, yes I'm confident (in my situation) that a battery solution is likely to be cheaper.

[Mike90250]

from a lifetime or TCO perspective you might be right, I haven't done that math. Not sure what the lifetime of a generator is TBH. But up front costs, yes I'm confident (in my situation) that a battery solution is likely to be cheaper.

That would be a very novel situation.

A manual start , manual transfer 15kw propane generator should cost < $15K installed, and have a lifetime of +20 years with simple oil changes and filters. Less than $60 year.
Deluxe auto everything, another $3K Should run a whole house, with careful energy management (no hot tub, limited electric cooking, minimal air conditioning, minimal electric heating.

A 4kw battery / inverter / solar will bu upwards of $25K and will run a small window air conditioner or 1 plug in heater, lights, tv/radio, computer and maybe your sump pump, only when you have sunny days. Rain, storm clouds, dust clouds, wildfire smoke, will shut the system down after 1 skipped day of charge. Flying lawn chairs smashing the array will also cause shutdown. Every 5 years, expect to replace battery bank, $7- 10K, everything else, expect 10 years, electronics, 20+ on PV panels.

[SunEagle]

from a lifetime or TCO perspective you might be right, I haven't done that math. Not sure what the lifetime of a generator is TBH. But up front costs, yes I'm confident (in my situation) that a battery solution is likely to be cheaper.

I am telling you that you have to do the math or you will be spending $$$$ more then you need for the times you want emergency power.

I just purchased a 12kw dual fuel (propane/gasoline) generator for $1200. While I already had a 50 amp receptacle for my RV I can use it to plug the generator in and power up quite a few things throughout my house. The cost for the receptacle, box, breaker, wire, plugs and misc items to make it happen probably cost me about $200. A 20lb propane bottle will provide me at least 8 hours for a 6kw load so or 48kWh. It will cost me maybe $40 for it.

So I doubt that a battery that can provide 48kWh in a day is going to cost less then the $1500 I spent for my generator. But if you think you can spend less on a battery system then go for it and enjoy. Just don't cry too much when your lights go out during the night as your battery turns to dead weight.

[J.P.M.]

f I haven't done that math. Not sure what the lifetime of a generator is TBH. But up front costs, yes I'm confident (in my situation) that a battery solution is likely to be cheaper.

And you haven't done the math because ?

Not saying you're wrong, but I'd suggest doing the math before you go further with a view toward using actual and recurring costs, and use, or learn about, life cycle costing before you start.

Do those things and start with a realistic set of assumptions and you may come to the same conclusions as others who just may have more experience and savvy in these areas than you.

Or not. Either way, you'll end up with more information than you seem to have at this time which is never a bad thing.

[jflorey2]

Hi Jflorey2, I already have the sunk cost of the prevously installed solar microinverter infrastructure. Originally I was regretting that decision (there are benefits not relevant to this thread), but now, hearing from 2 vendors that they support this config per above, it's not cheaper or simpler for me to change to a DC coupled solar solution unless I'm missing somthing.

Sorry to hear that.

Just be aware that AC coupled systems are definitely possible. But they are not simple, and to make them work well in off-grid mode requires skills that most installers don't have. If I were you I'd be asking detailed questions about how they limit charging when the battery is full, how the inverter will handle that rapid change in load and how long the batteries will last in a given scenario.

[Ampster]

Good news, Outback responded to my question and confirmed that their radian gs8048a-01 supports up to 6kw of direct-grid inverters (4048 supports 3kw). However, right now they don't protect the batteries from overcharging when in this configuration. They have a relay and 12vdc output to trigger a dump load when the batts are at certain batt voltage as a workaround. They expect a 2019 firmware update to fix this issue (via frequency shift to shutoff micros).

That is also what I am hearing from Outback as far as AC coupling a Skybox. I used to have an Ouback Radian at another location but sold the Radian when I rented out that house. I had given up on Outback supporting AC coupling then. Now, two years later and the introduction of the Skybox and they are committed. I am in a similar situation as you since I have an investment in a grid tie system and want to use the Skybox to enhance that system and give me the ability to trick that system to generate power when the grid is down.
That dump load workaround could work for me in the meantime if they don't get AC coupling done soon.