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Whole house generator + Hybrid Solar w/battery backup

Buttafly_kris

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Joined
May 7, 2020
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Hi All,

I'm a newcomer to the forum and the forum is great, I'm learning a lot reading through the various posts, great material. I'll try not to be too wordy. About 3 years back I purchased a Generac 16kW propane whole house generator with ATS, it's be installed and working fine but I live in the Bahamas and we get hurricanes. Last hurricane we had knocked out power for about 2 weeks my area, the generator worked through this but we had to get the propane tank filled every 4 days or so which was a whooping $400. Eventually I started turning the generator off during the day and relying on a few UPSs I have installed, waiting until they got to about 5% battery then turning the generator back on to charge them back up and do whatever else was needed but I let the generator run all night. This obviously wasn't very efficient for me and I started to look into and research solar started watching (watched just about all) of Will Prowse's videos for solar and followed just about every diypowerwall youtuber. (I'm a tinkerer myself)

I've been looking into MPP solar a lot and their hybrid inverters, the one thing I've had difficulty finding after literally scouring the net for months, is how to wire up the whole house generator with a hybrid inverter w/battery backup and still allow for net metering. I've read in a couple different forums that the inverter can back feed to and damage the generator, I see that MPP solar have inverters that seem to allow for it, but it says it works with inverter type generators which I don't think my generator is. I wanted to know if it was possible to do it with a inverter like a MMP solar hybrid or would I need a inverter like a more expensive outback unit that has a generator input. I was trying to explore my way around AC coupling as I'm half comfortable with electric circuits from doing small stuff around my home. I quickly realized that I'm not as knowledgeable in electricity as I think I am when I'm installing AC units and changing sockets / light switches around the house.

Oh, I don't have (and was hoping not to have to use) a critical load panel, the ATS is the one that has a big "throw" that just cuts power to and from the house during the outage, that runs into a 80a fused disconnect which then runs to my main panel.

I hope someone smarter than I am can point me in the right directions...
 
Welcome to the forums!

... how to wire up the whole house generator with a hybrid inverter w/battery backup and still allow for net metering.
Check with Sol-Arc, I believe their hybrid inverter is designed for it. The skybox shows a generator in their hookup schematic, so that might work too.

Otherwise it'll depend on the inverter, but you can probably use some combination of ATS/cutoff switches to isolate the solar system from the generator. Better to get something designed for it though, that should allow you to get a combination of solar and generator power.

Enphase's Ensemble will have a 60 A generator connection hook up, but it's not activated yet and they haven't announced what generators it will support. You could use a cut-off switch for now (DPDT to swap the load panel between the generator and smart switch), but they haven't released what generators they'll be compatible with yet.

1592865360353.png
 
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Thanks for the Feedback, I was really hoping that I would be able to do manually what those inverters like the Sol-Arc do automatically with a few extra transfer switches and or relays. I'm pretty into automation so Im wired to think "I'm sure I can automate that"...In either event, I appreciate the information.
 
... was really hoping that I would be able to do manually what those inverters like the Sol-Arc do automatically with a few extra transfer switches and or relays....
You can, but the setup would be very dependent on the inverter, even the hybrids generally have a pass-thru limit. You'll also find those transfer switches are pricey, so getting a device that does it for you could save $. The design would also be dependent on a number of things... such as should the generator be able to charge the batteries.

For example with an inverter that shouldn't see generator power ever...you could do something like the diagram below so the generator only kicks on when the grid is off and the batteries run out:
1592944091302.png
 
Check with Sol-Arc, I believe their hybrid inverter is designed for it. The skybox shows a generator in their hookup schematic, so that might work too.
Yes the Outback Skybox has a Generator input. It has less capacity, 5kW than the Sol Ark but a lower price.
 
Thanks, I'm looking at the outback radian now, I think I will go with the 8kW model. I was trying to save cost and use the Chinese models but looks like I'll have to pony up the $
 
Thanks, I'm looking at the outback radian now, I think I will go with the 8kW model.
If you need that kind of power then the Radian may be initially look to be the best value compared to stacking two Skyboxes. By stacking I mean running in parallel. I have had a Radian and a Skybox and Outback support is excellent. The Skybox is more modern and a true All in One inverter that has the ability to input TOU rates to take advantage of net metering. When you price the two side by side the Radian is a component system so in addition to the Radian you will need the BOS to accommodate the generator input, separate charge controllers, a Mate3 interface and a communication box for all of those to work together. A good online dealer like Alt E should be able to help you make the right decision. Amy from AltE is online here as @SolarQueen
 
Others beat me to the big answers but a tiny micro question in your description is if you don't have netmetering now you may not be able to do net meter with MPP solar as it is not UL listed. The other part being if you don't have critical load panel and just use ATS then you will not be able to net meter
 
Please keep us informed as you go, hopefully with pictures!
 
If you need that kind of power then the Radian may be initially look to be the best value compared to stacking two Skyboxes. By stacking I mean running in parallel. I have had a Radian and a Skybox and Outback support is excellent. The Skybox is more modern and a true All in One inverter that has the ability to input TOU rates to take advantage of net metering. When you price the two side by side the Radian is a component system so in addition to the Radian you will need the BOS to accommodate the generator input, separate charge controllers, a Mate3 interface and a communication box for all of those to work together. A good online dealer like Alt E should be able to help you make the right decision. Amy from AltE is online here as @SolarQueen

Okay, i will reach out to her as just reading this you have educated me on the outback systems so there's obviously a lot more conversation necessary before I made the decision here. thanks so much for the response.
 
Others beat me to the big answers but a tiny micro question in your description is if you don't have netmetering now you may not be able to do net meter with MPP solar as it is not UL listed. The other part being if you don't have critical load panel and just use ATS then you will not be able to net meter
netmetering is more of a "nice to have" for me, here in Bahamas it's like Florida, we have tropical weather year round, so I figured if I have to get a system, it would make sense for the system to assist with paying for itself. The must have is really to have the capability to have stored power for hurricane season in case we have a few days without power. Oddly enough, once a hurricane passes, it's normally beautiful weather just not a beautiful city, it would be great to harness some of that and have the generator only run when needed and save $$$ not having to buy propane. Thanks for the reply
 
Remember, I am only familiar with the Outbacks and Sol Ark. There are probably others from Schneider, SMA and others that may be a good match for your situation. Each has their plusses and minuses. Sol Ark does have a good comparison page which is obviously biased toward their product. I presume you are on a North American 240v electrical system.
 
Remember, I am only familiar with the Outbacks and Sol Ark. There are probably others from Schneider, SMA and others that may be a good match for your situation. Each has their plusses and minuses. Sol Ark does have a good comparison page which is obviously biased toward their product. I presume you are on a North American 240v electrical system.
I was primary just looking into Chinese made inverters because of their price. Any information that you provide for the US models is great information as I only started heavily researching them more recently. Yes 240v with neutral wires.
 
Your building codes may not require the UL compliance that mainland US codes require. That may give you options that we don't have.
 
Your building codes may not require the UL compliance that mainland US codes require.
No, I don't think it does, like I haven't heard of only being able to run critical loads on solar. I know of persons that run their entire house / store from solar. There is an approval process for netmetering but it doesn't seem to be very strict as I've also heard the rates aren't that great. I can probably get away with non-UL listed devices.
 
I think there may be some different understanding of critical loads. When the grid is up all my panels run off my solar and hybrid inverter. When the grid is down only the loads that I chose to wire into Subpanel A (loads that I consider critical) will be powered. That was a choice based on battery capacity and no generator. In your case with generator capacity you could have you whole house on that subpanel as shown in the diagram that @svetz posted.
 
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I think there may be some different understanding of critical loads. When the grid is up all my panels run off my solar and hybrid inverter. When the grid is down only the loads that I chose to wire into Subpanel A (loads that I consider critical) will be powered. That was a choice based on battery capacity and no generator. In your case with generator capacity you could have you whole house on that subpanel as shown in the diagram that @svetz posted.
Okay, I thought it was based on rules around critical loads, I didn't know it was choice based. If I could avoid it, I would like to stay away from rewiring for a critical loads panel only adding in / making changes what I need for solar. I just purchased a gas water heater and looking at a gas dryer, my highest draw would probably come from a new split AC units I have installed. 2 x 9000btu at 22 seer, 1 x 18,000 @ 18 seer btu and going to purchase a 36,000 btu at 21 seer. The ACs are actually wired to a sub panel as I was initially just thinking to run that panel on solar (it gets crazy hot here) but I didnt understand that much about solar back then thinking I could only run one panel. My generator is honestly overkill as I don't think I've every used more than 7-8 kW at any point and thats with my tankless water heater and all AC units running.
 
Inverter is not a big ticket item. I have MPP solar LV5048 which I have it wired to a critical load panel (plan on moving everything except the AC to that).
The accessories cost a big buck like the batteries and solar panels etc. LV5048 can be parallel connect upto 3 units that is 15kw capacity but the supporting batteries will drain the bank if you have to have everything off-grid. LV5048 can take the power from grid or generator to power the critical load panel and charge batteries but will not feed back to grid.
 
Inverter is not a big ticket item. I have MPP solar LV5048 which I have it wired to a critical load panel (plan on moving everything except the AC to that).
The accessories cost a big buck like the batteries and solar panels etc. LV5048 can be parallel connect upto 3 units that is 15kw capacity but the supporting batteries will drain the bank if you have to have everything off-grid. LV5048 can take the power from grid or generator to power the critical load panel and charge batteries but will not feed back to grid.
Thanks, I realized this as well, which is why I didn't want to spend $4000+ on just the inverter. I just wanted something that would run the house until the battery depleted then run the generator and cycle like that. Last hurricane my generator was on entire nights and not even running the AC units because I was trying to save propane. Maybe we were being paranoid but we even took short showers...$500 tank refills every few days adds up and then I was told with propane gensets you need to let it rest after 10/11 hours of constant running. I figure the solar would help me out a lot here, but I could be way off axis. For the batteries, I was looking into DIY powerwall solutions, I work in IT so getting laptop batteries is a easier for me than others. All in all, I'm thoughts are I should be about to spend about 8,000 - 10,000 and have something that can leverage the generator and work me through a couple days of power outages.
 
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