Need help choosing an inverter for 3kw (no grid tie)

scubaet · July 2017

I just purchased 13 - 230 watt solar panels used, I believe they put out 2200 watts currently.

Would like to install them on a house I am building with normal grid connection. The goal is to run all led lights in the house 100% solar, and possibly mini-split ac and well pump during full sun. Battery bank might be forklift type to start.

Goal is to reduce grid use as much as possible and draw from it as needed.

Is there an inverter with that capability that does not cost $4000? I know there are electric switch panels that allow you to toggle grid and solar for 6-10 circuits but has to be done manually.

Thanks

BB. · July 2017

A Grid Tied inverter (no battery connection/backup) is a lot cheaper to install and maintain. Do you have GT billing available from your utility?

Batteries make the system more expensive (to install and maintain)--Many times, for folks that have few power outages (I get an hour outage every few years, mostly from cars taking out power polls), a backup genset + stored fuel (or natural gas/propane) may be a "cheaper over time" solution.

-Bill

mcgivor · July 2017

scubaet said:

I just purchased 13 - 230 watt solar panels used, I believe they put out 2200 watts currently.

Would like to install them on a house I am building with normal grid connection. The goal is to run all led lights in the house 100% solar, and possibly mini-split ac and well pump during full sun. Battery bank might be forklift type to start.

Goal is to reduce grid use as much as possible and draw from it as needed.

Is there an inverter with that capability that does not cost $4000? I know there are electric switch panels that allow you to toggle grid and solar for 6-10 circuits but has to be done manually.

Thanks

What about a Schneider SW 4024 or 4048, allows load shaving, for offsetting peak billing, has grid pass through, batteries can be primarily for backup, generator support, with transfer switch, grid charging and much much more. It's a very versatile unit, if strictly grid tie is not what you are looking at.
https://www.solar-electric.com/schneider-electric-sw-conext-inverter-4048-120.html

littleharbor2 · July 2017

While it isn't going to save you any money, another approach is a small separate off grid battery/inverter set up. This can be assembled fairly inexpensively. You can run whatever loads on it that fit. I have a small 24 volt system at our on grid home and run the television, home theatre, satellite receiver and cordless phones on it. One benefit with this setup is when the grid goes down your off grid setup is still be fully functional.

Estragon · July 2017

For small constant loads like LED lights, a small 12v inverter with low tare losses like a Morningstar 300w pure sine wave could work well. To run larger loads like AC or pump, you would need to get specs on the loads to determine inverter needs. For example, they may be 240v and/or have large startup current requirements. Something like a Magnum 4448pae (4400watt, 120/240v,$2255 from our host) may work. It has an internal transfer switch that would use grid power if available.

As Bill mentioned, a battery based system will likely be considerably more costly than grid power.

Solray · July 2017

It's possible to use less power without installing anything by being aware of your use. We use very little just by using power switches to turn things off. The tv for example is on for only a couple hours a month on movie night. We both make our living using our computers, my wife sells art on ebay and I run my graphic design and Web Development business and my photography and music creation at home.

mcgivor · July 2017

Solray said:

It's possible to use less power without installing anything by being aware of your use. We use very little just by using power switches to turn things off. The tv for example is on for only a couple hours a month on movie night. We both make our living using our computers, my wife sells art on ebay and I run my graphic design and Web Development business and my photography and music creation at home.

Thats not the point, read the OP's original post, the panels are purchased, technical questions asked, we all know turning everything off and living in total darkness, or fractional divisions thereof, would be the best way to conserve energy, that's obvious. Why mention it?

scubaet · July 2017

mcgivor said:

What about a Schneider SW 4024 or 4048, allows load shaving, for offsetting peak billing, has grid pass through, batteries can be primarily for backup, generator support, with transfer switch, grid charging and much much more. It's a very versatile unit, if strictly grid tie is not what you are looking at.
https://www.solar-electric.com/schneider-electric-sw-conext-inverter-4048-120.html

Thank you mcgivor, that is exactly what I was looking for and thank you for the term "load shaving" I have been having a hard time with the lingo.

That inverter fits my stated goal above nicely "Goal is to reduce grid use as much as possible and draw from it as needed. "

The Conext SW inverters incorporate advanced features for modern grid-connected systems. The Conext SW inverters are consumption ready with the ability to prioritize solar consumption over grid, while maintaining zero grid export. The Conext SW can work with the grid to avoid peak utility charges and support the grid when utility supply is limited.

Thank you everyone else for the fast feedback, and I can use plenty more.

Responding to other comments:

Why I do not want grid tie:
- grid goes down, lights go out, solar panels are now worthless
- using your panels to get a credit from the power company of $100/mo or so, why not just use the solar panels to reduce your draw from the grid for the same savings? And you still have capability if the grid goes down.
- why spend $10k to save $100/mo?

We live in hurricane ally central Florida, so grid tie for me is not desirable. Need to be able to function two weeks without the grid, basic comforts lights water small ac etc...

We have a backup generator, but two weeks would require 200 gallons of onsite gas storage. or 1000 gallon propane tank.

Estragon: I do like the idea of running the led lights on a smaller dedicated inverter.

littleharbor2: RE having portions of the house dedicated off grid. I have been thinking of this using a transfer switch panel and inverter connected to this https://www.amazon.com/gp/product/B000BQN4T2 It's made for a generator but can put the inverter for that spot, the box allows to flip from grid to solar/gen and back. its a manual process but cheap.

And last everyones interpretation of price is relative to their priorities. I paid $800 or $0.27 cents a watt for my 5 year old 3kw panels. Forklift battery bank may cost $1k and the inverter $800-$2000 range, so possible with patience and research and help from you guys, I can have some self reliability for $3-$4k.

Thanks again for the info and any more suggestions are really welcomed.

Raj174 · July 2017

Hi scubaet,
I live in north florida and setup a hybrid system a little over a year ago. I use it for backup power and load shaving. It has cut my electric bill by about 50%, though that's only about 400 dollars a year. Keep in mind, it will not recoup investment costs, not even over 20 years. It's value is in assurance that you will not have to do without power.

It came in handy when hurricane Hermine blew through Tallahassee last September 1 and power was down for 5 days. We had power the whole time, however had to run the generator each night from midnight till about 4 in the morning. I have 3600 watts PV and a 4000 watt Outback Radian inverter and produce an average of about 10 kWhs per day.

If your going to go with 2200 watts PV ( though you will probably need to use either 12 or 15 panels) then I'd recommend a 48 volt system and the Conext SW 4048 would be a good match. It has a 30 amp transfer switch and you might want to put all your 120 volt loads on a sub panel powered by the inverter. That way in a power failure you would have lights, refrigeration, ceiling fans, and anything plugged into a 120V outlet. You might manage 8 kWhs a day if you can avoid any shading. Of course system size will depend on your power usage.

There are a lot of details to work out, battery bank, components, wiring and more. This forum will be an invaluable resource in helping you achieve your goal.

Rick

bill von novak · July 2017

scubaet said:

Why I do not want grid tie:
- grid goes down, lights go out, solar panels are now worthless
- using your panels to get a credit from the power company of $100/mo or so, why not just use the solar panels to reduce your draw from the grid for the same savings? And you still have capability if the grid goes down.
- why spend $10k to save $100/mo?

We live in hurricane ally central Florida, so grid tie for me is not desirable. Need to be able to function two weeks without the grid, basic comforts lights water small ac etc...

Then go hybrid. Hybrid allows both grid tie and independent backup. Inverters like the Radian will do that, as will smaller inverters (GVFX3648 for example will give you 3600W if you can live with 120V.) Radian will also give you a separate generator input without xfer switches.

Photowhit · July 2017

scubaet said;
We have a backup generator, but two weeks would require 200 gallons of onsite gas storage. or 1000 gallon propane tank.

I worry a little about your goals and costs. A Honda Eu2000 generator will run 10 hours at full load (1600 watts) That's 16 Kwh's of power. My forklift battery has 16 Kwh's of storage and weights 1100 pounds. You can only use @12Kwh's of the stored energy of the battery....

scubaet said:

And last everyones interpretation of price is relative to their priorities. I paid $800 or $0.27 cents a watt for my 5 year old 3kw panels. Forklift battery bank may cost $1k and the inverter $800-$2000 range, so possible with patience and research and help from you guys, I can have some self reliability for $3-$4k.

That is one cheap battery! Guess you are looking at reconditioned ones? Mine was $2525 delivered, rated by GB at 19Kwh's more realistically 16 Kwhs (they over rate their batteries)

Also remember you will need a charge controller ($500+,) and combiner box, wiring, mounting material and hardware...

Need help choosing an inverter for 3kw (no grid tie)

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