Confusion on meaning of Off Grid vs Grid-tie vs Zero Export

[Ampster]

I have been trying to figure out how to have power from the grid when the house is built and then add my own solar later.

I did not build a new house but the concept is the same. When I purchased the home, I knew I would have to replace the main service panel because it was unsafe. Therefore I bought a solar ready main service panel. That meant that it had a larger bus bar than the main breaker. It was located on one wall of my garage and I located two sub panels on the inside wall of that same garage. I designated one panel my critical or essential loads panel and the other my high loads panel. Those panels had 20 spaces for regular breakers or 40 spaces for half space breakers. The sub panels are close enough that if I change my mind on what is an essential load, I could swing the wires from one to the other. I also used wiring gutters on the top and botton for ease of rewiring. The top gutter contained all my load circuits and the bottom gutter was for the big cables from the main service panel to each of the subpanels.

Later when I installed solar it was a simple matter of putting the hybrid inverter on the same wall as the subpanels and wiring it through the wiring gutters. In the case of new construction the only thing I would add is a conduit from your roof to the area where your inverter is going to be. If you know your are going with micros, you do not need conduit like you would if you are running DC to your inverters. You just need to have a conduit from your attic to your roof and have your roofer flash that entry point. I did a self install and used micros for the grid tie capability. In retrospect, if I had known how much the power was going to go out, I probably would have started with a hybrid inverter with DC coupled solar and later incrementally added AC coupled solar with micros later. At least with a SolArk it is best to have a high ratio of DC coupled solar to AC coupled solar when the grid is down. AC coupled solar is easy to add incrementally to different roof pitches and orientation without the complications of matching MPPT inputs. As rates shifted in California it also became optimal economically to have some west facing panels to capture more of the solar at the peak rates that began at 4PM. My system is essentially grid tie but for most of the year I am able to be self sufficient and self consume much of my solar. I will never be able to be totally off grid because my winter loads are often greater that production, especially when we have weeks of cold cloudy weather.

 

[OffGridInTheCity]

Do you have design docs posted? Or can you share privately? I have been trying to figure out how to have power from the grid when the house is built and then add my own solar later.

Is your ATS using contactors or relays?

ATSs use mechanically linked relays - this is what ensures only 1 input at a time is allowed to pass thru to the output as both relays cannot close at the same time because of the mechanical interlink.

For US 240v/120v (L1, N, L2) up to 50a I use Progressive ATSs (ETL) - https://www.amazon.com/gp/product/B003VAWNVK/ref=ppx_yo_dt_b_search_asin_title There are installation youtubes. Feed the off-grid inverter output to the Gen Input for automatic default to Shore (Grid) Input. ATSs with ETL/UL larger than 50a are not cheap or easily available which is why I use several - to cover almost every circuit in the house.


For 120v up to 30a I use Go-Power ATSs (ETL) - https://www.amazon.com/gp/product/B00153EYTO/ref=ppx_yo_dt_b_search_asin_title Similar to Progressive, there are youtubes on these, they are popular for RVs.

I use an ATS/MTS combination at my main house panel to select critical circuits and the MTS let's me flip switch's to vary the overall load on the solar system. The ATS/MTS provides the same role as a 'critical loads panel' but with auto switch-over (ATS) instead of manual interlocked breakers and individual circuit switching between (MTS) as apposed to all or nothing circuits at the critical loads sub-panel. Using multiple ATS/MTS(s) I could do every circuit in the main panel this way - but 10 circuits is enough for my purposes.


And then I use a couple more ATSs here and there. Each one can do up to 240v/120v @ 50a worth of circuits.
For example, I use 1 at the Heat-Pump outdoor compressor. Installed it by intercepting the original wiring for grid AC (from main house panel) and ran inverter AC over to it (from Inverter distribution panel) and then out to the compressor.



The inverters go to distribution panels and these have breakers / wiring out to the ATSs.....

 

[plympton]

I'll chime in my story - I dithered for about a year before pulling the trigger on a mini-system. Like others, I got a quote for $50k (without a new roof, which I needed!) after subsidies, and... ended up here.

I installed a glorified UPS - Bluetti AC300 + 6 kWh batteries + 6 400w panels. The inverter feeds a transfer switch that handles about 80% of my constant use loads - fridge, freezer, furnace, servers, and room AC. If solar comes on-line, it charges the batteries and uses it. Even on this rainy, cloudy March day, I'm still pulling 600w right now (noon).

Nothing ever, ever, ever goes back to the grid. Technically, it's a portable system. The pros are it was cheap (under $4k) & totally DIY. The downside is that I'll be generating 70 kWh / day in July and won't be able to use most of it. If I was grid-tied I could 1:1 bank it. A bigger system would have been better, more professional, but wouldn't allow me to tinker & learn, and taken 10+ more years to pay off.

If all I do is offset my constant loads, I'll save $900/year and have a backup in case (something) happens.

Edit: I said I might generate 70 kWh / day in July. That's insane. I have 2.4 kW of panels. 70 / 2.4 would be 29 hours of full generation a day. My new estimate is about 17 kWh in July, based on this posting by a fellow PDX'er. That's still enough evidence that I decided to add 2 5.1 kWh batteries to my original 6.

 

[1201]

Maybe technically, but I ran my Sol-Ark 15k without battery the first few months. It really comes down to what options you want.
You can install a hybrid inverter and never use batteries, but have the option to add later.

That would be a very good option for what the OP is trying to do. but Im not sure if OP is wanting to pay $7000 for an inverter. I might be wrong

 

[wpns]

That would be a very good option for what the OP is trying to do. but Im not sure if OP is wanting to pay $7000 for an inverter. I might be wrong

$5200 for the EG4 18Kpv checked all yhe boxes for me.

 

[timselectric]

Inverters that can mix grid and solar at same time are expensive. With the affordable batteryless inverters if you don't have enough pv to power the loads they will switch completely to grid, or shut down.

Not completely accurate.
Many off grid AIO's have a SUB mode.
This can blend solar and grid.
If they are capable of batteryless operation, the grid is the buffer.
This is how I was setup in the beginning. While waiting for my first battery to arrive.
Solar covered everything it could and grid covered the rest. (Or all at night)
It's an inexpensive way to get started.
If you just want to start with reducing your utility bill.

 

[MajicDiver]

Is it an "off grid" inverter I need? I want "zero export" (another term I keep seeing). I understand grid-tied can feed back to the grid (not what I'm looking for).

The simple fact is the terms are used very inconsistently. The various manufacturers use them inconsistently as do the many websites and store fronts as well as users of this forum.

I am off grid using inverters that most people on this forum call gridtied inverters.

Everyone has opinions, these are my suggestions to you:

1. You have taken some initial steps at education. But YouTube can be significantly incorrect and misleading. Start also down loading and reading manuals and installation guides of the systems that interest you. Sometimes they are on the seller websites, sometimes they are on a manufacture website. Some sites will have 3-5 year old obsolete manuals others will update as new info is published.

2. When evaluating the many pieces of advice you are getting on this forum, pay attention to the detail provided. Some people put a lot of effort into explaining the reason they are suggesting something- pay attention to those.

3. Also, a good many people have described their system in some detail in their profiles, look there for nuggets to ponder. You can read the description in the “about” section of my profile to get an overview of my system-if that interests you post questions. I’d suggest doing that with the users who are providing you with recommendations. If someone has not taken the time to describe their system in there profile, I would suggest that they probably are not taking the time to make a quality recommendation to you that is on solid technical ground.

 

[timselectric]

If someone has not taken the time to describe their system in there profile, I would suggest that they probably are not taking the time to make a quality recommendation to you that is on solid technical ground.

Not necessarily.
You won't find much about my system in my profile.
It's all in my build thread.
And some of my recommendations are decent.

 

[MajicDiver]

And some of my recommendations are decent.

Totally agree. I like understanding what someone has built when evaluating what they say. Perhaps you might link to your build thread in your profile? I would have found it quicker if you did. I was here a long time before I say it.

 

[timselectric]

Totally agree. I like understanding what someone has built when evaluating what they say. Perhaps you might link to your build thread in your profile? I would have found it quicker if you did. I was here a long time before I say it.

It's linked at the bottom of my posts.

 

[1201]

Not completely accurate.
Many off grid AIO's have a SUB mode.
This can blend solar and grid.
If they are capable of batteryless operation, the grid is the buffer.
This is how I was setup in the beginning. While waiting for my first battery to arrive.
Solar covered everything it could and grid covered the rest. (Or all at night)
It's an inexpensive way to get started.
If you just want to start with reducing your utility bill.

You're absolutely right- I stand corrected- there are some lower price inverters that can blend grid and pv

 

[timselectric]

You're absolutely right- I stand corrected- there are some lower price inverters that can blend grid and pv

Most use a double conversion for the function, I believe.
But mine actually acts like a hybrid. Even though it's classified as off grid. (Guess how I know this. lol)

 

[1201]

Most use a double conversion for the function, I believe.
But mine actually acts like a hybrid. Even though it's classified as off grid. (Guess how I know this. lol)

How do you know this, lol

 

[MajicDiver]

It's linked at the bottom of my posts.

I’m confused,I don’t see a link in your post?

 

[timselectric]

I’m confused,I don’t see a link in your post?

 

[Tulex]

View attachment 203857

LOL, I keep clicking on this bold text, nothing happens.

 

[hwy17]

I don't think a lot of the marketing terms stand up to linguistic scrutiny. Hybrid seems ok, but it's ambiguous: Hybrid of what?

I would make two categories:

Grid tied or Grid Following - Can only operate with an external AC supply to support. Includes micros, regular string inverters, most 1500v solar and battery systems.

Grid forming or Grid Interactive - Capable of forming it's own independent AC output.

Almost everything we discuss on this forum firmly falls into the latter category. It's really the grid tied inverters that make a grey area when they do things like SMA sunny boy's emergency solar only output or enphase's solar only function.

"Off grid" inverters barely exist. Inverters called that are almost all grid interactive. Maybe Outback made some stationary install off grid inverters without grid interaction capability?

 

[timselectric]

I don't think a lot of the marketing terms stand up to linguistic scrutiny. Hybrid seems ok, but it's ambiguous: Hybrid of what?

I would make two categories:

Grid tied or Grid Following - Can only operate with an external AC supply to support. Includes micros, regular string inverters, most 1500v solar and battery systems.

Grid forming or Grid Interactive - Capable of forming it's own independent AC output

I try to stay away from the terms "grid forming" and "grid following". Because they already exist and are actually the opposite of what you would think. (Too confusing)

 

[timselectric]

There are 3 categories.

"Grid-tied" , sends all production to its grid connection and relies on the grid to function.

"Off grid" , sends all production to battery, to be used emidiatly or in the future.

"Hybrid" , a combination of both above.

 

[hwy17]

I try to stay away from the terms "grid forming" and "grid following". Because they already exist and are actually the opposite of what you would think. (Too confusing)

I have heard what you are saying but I'm not sure I'm convinced. Grid Forming in utility has been used to describe inverters that provide voltage support but cannot actually run standalone, which confuses things. But conceptually I think the terms are still weighted towards their linguistic meaning.

Grid Forming vs Grid Following ?

Grid forming and grid following inverters are both important technologies for integrating renewable energy sources into the power system.

energycentral.com

 

[timselectric]

I have heard what you are saying but I'm not sure I'm convinced. Grid Forming in utility has been used to describe inverters that provide voltage support but cannot actually run standalone, which confuses things. But conceptually I think the terms are still weighted towards their linguistic meaning.

Grid Forming vs Grid Following ?

Grid forming and grid following inverters are both important technologies for integrating renewable energy sources into the power system.

energycentral.com

That's only one source for the definitions.
And I could almost go along with their interpretation.
But, it's not the majority.
So, I just avoid the terms.

 

[Ampster]

I’m confused,I don’t see a link in your post?

Those links do not show up on small screens of phones and perhaps some tablets.

 

[MajicDiver]

"Hybrid" , a combination of both above.

I don’t disagree with your statement, but the issue is that the various combinations and variations that fit the definition make the term useless in describing anything specific. Telling someone an inverter is a hybrid tells them nothing about the inverter.

 

[timselectric]

Those links do not show up on small screens of phones and perhaps some tablets.

Yup, just checked my phone. It doesn't.
I'm always on tablets, it does show on mine. Not sure about others.

 

[MajicDiver]

Those links do not show up on small screens of phones and perhaps some tablets.

That didn’t occur to me. I don’t recall how I found his build thread last year, but it probably was on one of the rare times I was on a computer……