Trying to understand Off-Grid vs On-Grid, PV and battery Backup

[adamantium]

Grid tied and grid interactive are the same thing.
Grid-tied is a bidirectional connection.
An off grid AIO only connects to the grid as a load.
I can see how this terminology can be confusing. Especially when it gets repeated incorrectly a lot.

I agree, I can see how you are confused.

How grid-interactive differs from grid-tied
Grid-tied systems feed green energy into the electricity grid but must disconnect if the grid goes down. Tied systems receive credits and incentives for feeding green power into the grid but they can’t generate energy for their own use when grid electricity is unavailable.

Grid-interactive systems also feed power into the grid but they can keep generating green energy from their PV modules and battery backup systems and use this electricity to meet their own needs.

Benefits
A grid-interactive PV system offers many benefits:

• Feeding green energy into the grid when it benefits you and disengaging when it does not
• Independence to use your own clean solar and battery power in your home or business during a grid power failure
• Accessing any credits and benefits that are available for tying to the grid
• Ensuring fuller use of the clean PV power you produce, whereas in off-grid systems much of the clean energy goes to waste
• Two equally available sources of power
• A more reliable power supply and lower costs
• Contributing to a more sustainable energy future

I don't recommend expensive equipment with a lot of features that aren't needed. (Depending on specific needs) no point in paying extra for Grid-tied and AC coupling capabilities, if you aren't going to use them.

I don't see limiting your total power by your battery charger and your inverter's output capability especially if you still require the grid. No point in paying more money for less power, less functionality and old technology.

 

[timselectric]

I give up.
Not banging my head against this wall, anymore.
It's just a waste everyone's time.

 

[400bird]

Timselectric, can you post another 163 times? That would put you at exactly 100x more posts than adamantium.
49 vs 4,737

This is why I hate the naming and labeling. None of it is standardized all of the technician content is mangled by the marketing departments.

 

[timselectric]

Timselectric, can you post another 163 times? That would put you at exactly 100x more posts than adamantium.
49 vs 4,737

This is why I hate the naming and labeling. None of it is standardized and l of the technician content is mangled by the marketing departments.

No point.
You can lead a horse to water, but you can't make them drink.
And yes, marketing will say anything, if it makes something appear more shiny.

 

[adamantium]

No point.
You can lead a horse to water, but you can't make them drink.
And yes, marketing will say anything, if it makes something appear more shiny.

Look Tim, this isn't about winning an argument with you. Its about what you said, stopping the spread of misinformation about ideas and some of the terms used in the industry. You made assumptions and statements about what I proposed that were simply incorrect. You don't appear to know anything about hybrid or grid interactive inverters, yet you dinged me for proposing a solution that you perceived to be a mismatch for what the member had asked for. Then you got frustrated when I corrected you. Believe me I am not ignorant, and I would suggest humbly that you go do some research on more up to date inverter technologies. Hybrids have been around for quite a while now and AIO, although they sound like they are sufficient for everyone's needs, and have quite a following on YouTube, they aren't the best choice in this case. Now I haven't posted nearly as many times as you have, but I don't believe that has any bearing whatsoever on a person's qualifications to speak about a subject. In fact it may have an inverse correlation. So don't take your ball and go home, let's just get along and answer the member's questions and help him out. I really don't care what he buys and I'm not tied in anyway to any organization doing any kind of advertising or marketing. I am not deceived by slick ads or lured by shiny objects, and I'm not a horse. I just like technology like pretty much everyone else here in this forum. Probably including you. No hard feeling I hope.

 

[PuraVidaPrepping]

I have used the Sol-Arks and the Deye base units in full off grid and grid interactive scenarios, all without grid feed back. I absolutely use them almost exactly as is needed in the original post. The new Sol-Ark 15k or GSL 12k will be the simplest install / lowest maintenance way of seamlessly offsetting the usage without limiting to inverter / battery capacity. Either if these can handle the entire loads panel without overload, and anything beyond the inverter capacity is brought in from grid without switchover or need of external transfer switch.
Once you consider the integrated transfer switch, the 3 high end charge controllers, and the power of inverter / customizable smart load options, yes they are expensive, but less than if you had to do all those things separately.

 

[Vigo]

So am i the only one who thinks it isn’t timselectric’s fault that the term ‘off-grid inverter’ doesn’t mean it has no grid connection? Because that IS dumb, it’s clearly a problem even for.. very smart people.. and it’s also.. not timselectric’s fault. ?‍

To me the main thing to be decided is whether to buy cheaper inverters and leave the loads side alone and deal with the fact that the house will switch ENTIRELY to grid whenever loads (briefly?) exceed the inverters’ instantaneous capacity, or whether to spend more on inverters OR rewire some of the loads (or both) so that the grid only supplies demand that is in excess of inverter supply, without ever switching the loads 100% onto grid other than in the most severe conditions. Maybe there’s a more concise term to describe that, but no matter how concise there will still be someone misunderstanding it and wanting to fight about it..

 

[schmism]

my dual growatt 5500w PV system has been operational for almost 2 years now. does everything OP wants with a critical loads pannel. which considering the work to install the PV system is minor addition. On good sun days my critical loads panel (about half my house) is completely off grid for days on end. In poor sun days I'm on grid and there is no difference. The reality is, I'm able to reduce my power bill by ~$100 a month (or at least it used to be before my power rate basicly doubled... thanks to the MISO summer power auction jumping from $5 to $236). I've avoided (like i didnt know the grid was down) 3 diffrent grid out periods (between 2 and 12 hrs) and I have backup incase of long term power outage.

 

[Pierre]

So am i the only one who thinks it isn’t timselectric’s fault that the term ‘off-grid inverter’ doesn’t mean it has no grid connection? Because that IS dumb, it’s clearly a problem even for.. very smart people.. and it’s also.. not timselectric’s fault. ?‍

To me the main thing to be decided is whether to buy cheaper inverters and leave the loads side alone and deal with the fact that the house will switch ENTIRELY to grid whenever loads (briefly?) exceed the inverters’ instantaneous capacity, or whether to spend more on inverters OR rewire some of the loads (or both) so that the grid only supplies demand that is in excess of inverter supply, without ever switching the loads 100% onto grid other than in the most severe conditions. Maybe there’s a more concise term to describe that, but no matter how concise there will still be someone misunderstanding it and wanting to fight about it..

I agree - lots of confusion with the terms. To me an off grid inverter is not connected to mains at all. It can use a generator as the mains input and PV for DC to AC. Maybe what you need is something like the Growatt 5000 ES that has grid assist / pass through. No need to rewire / split your panel - if your loads exceed the inverter capacity your service mains will supply the balance. Also this inverter cannot feed back to the grid. Just make sure that this inverter is up to code where you live.

 

[Ampster]

Most brand name full-house inverters are hybrid inverters not AIO inverters.

Those terms are not mutually exclusive. Outback makes two hybrids that are also All In Ones, the Skybox and the Mojave. The SolArk is a hybrid that is also All In One. I think you and @timselectric are splitting hairs and are probably on the same page conceptually

 

[Ellcon123]

To me, an off-grid inverter is one that cannot supply power to the grid. It may have ac in with built in ATS, but that's for when the battery/solar runs out. A GTI can feed the grid and traditionally would only work if the grid was present. There are hybrids now that blur the lines but an off-grid inverter is still just that.

 

[Vigo]

Maybe what you need is something like the Growatt 5000 ES that has grid assist / pass through. No need to rewire / split your panel - if your loads exceed the inverter capacity your service mains will supply the balance.

Unfortunately the Growatt 5000 does not do that. It either carries the whole load on inverter and does nothing with the ac input, or switches the ENTIRE load over to the ac input with its transfer switch, and attempts to simultaneously charge batteries from that ac input, up to a charge current limit you can set in the software. Unfortunately, it doesn't let you cap the actual AC input, just the dc charge current derived from it. That means when it is in bypass the total AC input to it is whatever the load is, plus however many watts of charging current you allow. You can't set a limit on that sum total. That doesn't really matter when the AC input is the grid, but it's irritating when your ac input is a generator.

Some other brands like Victron have the feature you're describing. This is why I described the decision as 'invert as long as you can and then switch 100% to grid, or invert up to a point and then supplement with grid power'. That will dictate the inverter options that are available to you. You can also do a homebrew version of this idea by having something like the Growatts activating a grid-powered battery charger using its dry contacts. It could still be set to bypass entirely to grid in the case of low voltage or inverter overload, but activating a sufficiently sized grid charging source would probably reduce the occurrence of that down close to nothing if your charger was anywhere near the size of your overnight loads.

When i first went off-grid and did not have enough battery, i experimented with 'offsetting' drain by feeding the battery a fixed charge source that was less than the actual load. It didn't stop the battery from draining, it just slowed the drain enough to make it to morning. I am still experimenting on doing this between a lithium bank and a lead bank. I transferred 2.5kwh from lithium to lead last night through a fixed ~200w 'charger' and then recharged 2.6kwh today while the sun was up. So your AC charge source would just have to 'offset' your discharge enough to keep the system up til morning, with the internal transfer switch being the backstop that will switch you to grid if your plan doesn't work out every single time.

 

[Pierre]

Unfortunately the Growatt 5000 does not do that. It either carries the whole load on inverter and does nothing with the ac input, or switches the ENTIRE load over to the ac input with its transfer switch, and attempts to simultaneously charge batteries from that ac input, up to a charge current limit you can set in the software. Unfortunately, it doesn't let you cap the actual AC input, just the dc charge current derived from it. That means when it is in bypass the total AC input to it is whatever the load is, plus however many watts of charging current you allow. You can't set a limit on that sum total. That doesn't really matter when the AC input is the grid, but it's irritating when your ac input is a generator.

Some other brands like Victron have the feature you're describing. This is why I described the decision as 'invert as long as you can and then switch 100% to grid, or invert up to a point and then supplement with grid power'. That will dictate the inverter options that are available to you. You can also do a homebrew version of this idea by having something like the Growatts activating a grid-powered battery charger using its dry contacts. It could still be set to bypass entirely to grid in the case of low voltage or inverter overload, but activating a sufficiently sized grid charging source would probably reduce the occurrence of that down close to nothing if your charger was anywhere near the size of your overnight loads.

When i first went off-grid and did not have enough battery, i experimented with 'offsetting' drain by feeding the battery a fixed charge source that was less than the actual load. It didn't stop the battery from draining, it just slowed the drain enough to make it to morning. I am still experimenting on doing this between a lithium bank and a lead bank. I transferred 2.5kwh from lithium to lead last night through a fixed ~200w 'charger' and then recharged 2.6kwh today while the sun was up. So your AC charge source would just have to 'offset' your discharge enough to keep the system up til morning, with the internal transfer switch being the backstop that will switch you to grid if your plan doesn't work out every single time.

Are you using a 5000ES with 240v 50Hz single phase ?

 

[Vigo]

It is set to 240v 60hz in my case, but yes.

 

[adamantium]

Those terms are not mutually exclusive. Outback makes two hybrids that are also All In Ones, the Skybox and the Mojave. The SolArk is a hybrid that is also All In One. I think you and @timselectric are splitting hairs and are probably on the same page conceptually

Yea they're not. maybe I could have been more concise in my wording there. Hybrids are AIOs. When I said that most brand name full-house inverters are hybrid inverters not AIO inverters, what I meant was that hybrids are not just traditional off-grid all-in-ones. I was not saying that hybrids can not be classified as all-in-ones. You have to take into account the context of what was being discussed, and that was, that all that was needed for the OP to achieve the his desired outcome was a couple of traditional off-grid AIOs and the limitations that come with them. So I was specifically addressing that fallacy.

Now here's the point. Everything in this thread is irrelevant to the OP unless it addresses his desired outcome. He already described, and I further outlined what that was. Trying to convince the OP that his desired outcome is wrong, ill-advised or impossible when it isn't, is not the purpose of this forum. This thread has nothing to do with vocabular or misunderstandings in the industry. It has to do with what type of system he needs to achieve his desired outcome. Interestingly, the OP hasn't been heard or seen since he wrote that the off-grid AIO solution would not work for him, yet the thread goes on.

 

[Vigo]

all that was needed for the OP to achieve the his desired outcome was a couple of traditional off-grid AIOs

I agree. This should have stayed simple. It seems to me the point where it sort of derailed was talking about what happens when you overload the inverters and switch to grid:

my first question is what happens if i need 150A of power and the inverters can't deliver?

your system will shutdown and leave you without power. Until you restart it.

Mine have a setting to restart on overload.

Yes, mine is set for the same thing.

Take out those 4 sentences and you can kind of see where it fell apart. When you overload an offgrid AIO it doesn't have to just 'turn off the whole house until you go mess with it'. IT CAN SWITCH TO GRID! SEAMLESSLY!

I understand the caution of not wanting to use that setting until you understand what things in your home can cause the inverters to overload, and whether or not that could cause an endless loop of chattering transfer switches that ends up damaging equipment. That's reasonable precaution! But i think the end goal of 'buy AIOs and when they overload you switch to grid and barely notice, and later it switches back to battery+solar automatically' was lost sight of in the discussion. But it remains true that "all that was needed for the OP to achieve the his desired outcome was a couple of traditional off-grid AIOs."

Then the other wrench that got thrown in was

if i need 150A

Because most combinations of 2 matching AIO's won't have transfer switch capacity totalling 150a+. Thankfully this is also not hard. Firstly, the likelihood of it ever actually needing 150a+ for long enough to overload 12kw worth of AIO's is low, given that they'll do ~100a in overload for a few seconds before shutting down and OP probably doesn't have 100a+ of non-surge loads anyway. If op DID have a load that would run out the overload timers on the inverters and actually shut them down (which would need to be established!), there are 2 options:

• If that situation occurs often, build in enough inverter+battery to handle it without shutting down (price goes WAY up)
• If that situation DOESN'T occur often and 99% of your usage falls below 12kw, just forego the internal transfer switches and wire an appropriately rated transfer switch AFTER the inverters. (price changes by a few hundred bucks)

You can disable 'overload bypass' such that the ac input to the inverters would still charge batteries to recover inverter function, but not actually feed AC output and put the whole load of the house through the inverter's transfer switch. In my Growatts this is setting #18, im sure others have something similar.

Overload bypass:
When enabled, the unit
will transfer to line mode
if overload occurs in
battery mode.

Disable that, wire in an external transfer switch. At that point you have this:

And unless i'm missing something, that is simple and a lot cheaper than trying to buy 150a aka 36kw worth of inverters for a situation that probably happens <0.1% of the time IF it ever happens at all. IF it ever happens at all, you have to modify the statement to:
All that was needed for the OP to achieve the his desired outcome was a couple of traditional off-grid AIOs and an appropriately rated external transfer switch. Which is a heck of a lot cheaper than the 3rd inverter, let alone the 6 total inverters (+batteries) you'd have to buy if you wanted to use those EG4s to feed a 150a continuous load which may not even exist. Goes back to what Tim was saying: "no point in paying extra for [XYZ] capabilities, if you aren't going to use them." The original 2 inverters with the possible addition of an external transfer switch is the most economical way to hit the majority of the needs with solar and batteries.

 

[adamantium]

And my point was that it is simpler than that. All he needs is a more modern hybrid with a 200A pass-through, self consumption, and zero export. You can get these now for less money than any other option, and its less work. Just put the hybrid between the service panel and his existing load center for the house, and attach some batteries and his solar panels, and you are done.

And for the record, the OP states that he has a 200A service in another thread.

 

[Vigo]

hybrid with a 200A pass-through, self consumption, and zero export. You can get these now for less money than any other option, and its less work

Ok, i wasn't aware there was a unit with a 200a passthrough that cost less than 2x EG4 and an external transfer switch! I gotta read up! lol

As far as 200a service, i still say it depends what is actually in that house and being used. Because how big of a service you get is determined VERY unscientifically with a huge amount of headroom since it typically goes in before the actual structure and is basically legally required to be oversized. I think the amount of people who've popped a ~150a breaker at home (ie stayed above that for a long enough period) is pretty dang small as a percentage. I've only popped a 100a breaker with continuous loads one time in my life.

 

[adamantium]

I think the amount of people who've popped a ~150a breaker at home (ie stayed above that for a long enough period) is pretty dang small as a percentage. I've only popped a 100a breaker with continuous loads one time in my life.

I agree. Most houses have a 100A service, at least in my state. I've never tripped a 100A breaker even with two central air conditioners, electric dryer, range, dishwasher, freezer, multiple microwaves, refrigerators, TVs and more. But I live in a typical suburban neighborhood. If you live in a mansion, on a farm, have a shop, need to pump water etc., then it is different.

 

[30362]

I agree. This should have stayed simple. It seems to me the point where it sort of derailed was talking about what happens when you overload the inverters and switch to grid:




Take out those 4 sentences and you can kind of see where it fell apart. When you overload an offgrid AIO it doesn't have to just 'turn off the whole house until you go mess with it'. IT CAN SWITCH TO GRID! SEAMLESSLY!

I understand the caution of not wanting to use that setting until you understand what things in your home can cause the inverters to overload, and whether or not that could cause an endless loop of chattering transfer switches that ends up damaging equipment. That's reasonable precaution! But i think the end goal of 'buy AIOs and when they overload you switch to grid and barely notice, and later it switches back to battery+solar automatically' was lost sight of in the discussion. But it remains true that "all that was needed for the OP to achieve the his desired outcome was a couple of traditional off-grid AIOs."

Then the other wrench that got thrown in was

Because most combinations of 2 matching AIO's won't have transfer switch capacity totalling 150a+. Thankfully this is also not hard. Firstly, the likelihood of it ever actually needing 150a+ for long enough to overload 12kw worth of AIO's is low, given that they'll do ~100a in overload for a few seconds before shutting down and OP probably doesn't have 100a+ of non-surge loads anyway. If op DID have a load that would run out the overload timers on the inverters and actually shut them down (which would need to be established!), there are 2 options:

• If that situation occurs often, build in enough inverter+battery to handle it without shutting down (price goes WAY up)
• If that situation DOESN'T occur often and 99% of your usage falls below 12kw, just forego the internal transfer switches and wire an appropriately rated transfer switch AFTER the inverters. (price changes by a few hundred bucks)

You can disable 'overload bypass' such that the ac input to the inverters would still charge batteries to recover inverter function, but not actually feed AC output and put the whole load of the house through the inverter's transfer switch. In my Growatts this is setting #18, im sure others have something similar.

Disable that, wire in an external transfer switch. At that point you have this:
View attachment 108227
And unless i'm missing something, that is simple and a lot cheaper than trying to buy 150a aka 36kw worth of inverters for a situation that probably happens <0.1% of the time IF it ever happens at all. IF it ever happens at all, you have to modify the statement to:
All that was needed for the OP to achieve the his desired outcome was a couple of traditional off-grid AIOs and an appropriately rated external transfer switch. Which is a heck of a lot cheaper than the 3rd inverter, let alone the 6 total inverters (+batteries) you'd have to buy if you wanted to use those EG4s to feed a 150a continuous load which may not even exist. Goes back to what Tim was saying: "no point in paying extra for [XYZ] capabilities, if you aren't going to use them." The original 2 inverters with the possible addition of an external transfer switch is the most economical way to hit the majority of the needs with solar and batteries.

At the risk of re-igniting too much of this conversation, I'm installing two parallel EG4 6500-48s with ~3.9K of PV each (16 panels to start, maxing out PV at 32 panels early next year) and 30K of EG4 batteries.

With the ~60amp in from grid to each (for grid-assist) and ~60amp out from each to a 240v dedicated loads panel, what type of transfer switch, like you show in your diagram above, do you recommend and how do I trigger that in the event of overload? I assume the host inverter (2P1) uses a relay or contact output?