Supplement grid load with solar

[wsteelenyc]

I am looking at a few hybrid inverters from MPP and Growatt and I'm curious if they can pull the excess load from the grid when the solar is not sufficient for a load. I.E. if I am making 600w but my load is 1000w will the excess be pulled from the grid or do they just switch to grid power entirely. I'm currently using a grid tie inverter with a limiter that measures the power draw and never puts back in more than I am using, but a hybrid inverter, assuming it does what I mentioned it could accomplish the same and more as I could also use it for charging my batteries and inverting. I recently upgraded from 400w to 1200w of solar panels and have to upgrade some equipment and I'm thinking a hybrid solar inverter might be my best option so I can replace separate inverter, MPPT controller, grid tie inverter (with limiter) and battery charger.

 

[Coil]

I can't speak to Growatt but that is exactly what my MPP LV2424 does. Solar and utility will power the loads at the same time if solar is insufficient. From the manual for setting #1 on my model:

"Solar energy provides power to the loads as first priority. If solar energy is not sufficient to power all connected loads, Utility energy will supply power to the loads at the same time."

 

[Yankeroo]

I can't speak to Growatt but that is exactly what my MPP LV2424 does. Solar and utility will power the loads at the same time if solar is insufficient. From the manual for setting #1 on my model:

"Solar energy provides power to the loads as first priority. If solar energy is not sufficient to power all connected loads, Utility energy will supply power to the loads at the same time."

Is your LV2424 the green one? It seems there are several models that have the same "LV2424".
Regardless, to supplement the load my house is using with solar, I just plug the 'AC In' into any old outlet in the home and enable the grid tie option? Seems too easy, like I am missing something...

 

[Coil]

Is your LV2424 the green one? It seems there are several models that have the same "LV2424".
Regardless, to supplement the load my house is using with solar, I just plug the 'AC In' into any old outlet in the home and enable the grid tie option? Seems too easy, like I am missing something...

Setting aside for a moment the fact these are not UL listed and should not be grid tied in in the USA:

That is exactly how they work. I split a 12 gauge extension cord and wired one end to the AC output where I plug in the loads and the other goes into the wall for drawing grid power when needed. Yes, you could turn on the grid tie and it would back feed but it's entirely likely you would be breaching the appropriate upper voltage limits on that breaker at times of high production. But yes, you could.

The proper way to do that is with a transfer switch, but technically the function of the inverter is as you summarized.

Edit: Yes, mine is the green one. That was what "Hybrid" denotes.

 

[Yankeroo]

Setting aside for a moment the fact these are not UL listed and should not be grid tied in in the USA:

That is exactly how they work. I split a 12 gauge extension cord and wired one end to the AC output where I plug in the loads and the other goes into the wall for drawing grid power when needed. Yes, you could turn on the grid tie and it would back feed but it's entirely likely you would be breaching the appropriate upper voltage limits on that breaker at times of high production. But yes, you could.

The proper way to do that is with a transfer switch, but technically the function of the inverter is as you summarized.

Edit: Yes, mine is the green one. That was what "Hybrid" denotes.

My objective is to utilize as much of the PV generated power as possible. Currently, once my battery bank is full, the excess power floats off into space. What's my best option to utilize the excess power generated here?

 

[Coil]

There are several ways to address that and it really depends on your priorities. For instance, I like to keep my battery mostly full most of the time so I'm prepared in the event of an outage that could come at any time. So outage preparedness is a priority for me. Because of that my strategy involves powering a lot of my power hungry electronics (servers, desktop machines etc) with the inverter output. However, there are simply not enough of them to use all of the available power at peak production so I also have a window AC unit to use excess power that comes on during the peak hours of the day. Since I would be cooling my house regardless, this just transferring work from my central HVAC to this little window unit.

If keeping a full battery isn't your main priority, then the easiest strategy would be to let the battery run down overnight until you hit the low voltage cutoff at which point the inverter will switch to grid power and your battery will refill and run your loads during the day. If the size of the loads, the battery capacity, and your array size are properly balanced you would basically end the day with a full battery and repeat the cycle.

One of the "cons" of the latter approach compared to the former is the efficiency loss from charging/discharging the battery and the resultant tax on your battery life.

Finally, you could of course enable the feed-to-grid option. If you ignore the code violations inherent in this approach you would get the benefits of both. For what it's worth, an array of the size you're describing isn't going to overvolt a circuit especially if you have some constant loads also drawing power.

 

[Yankeroo]

My priority definitely aligns with yours, keeping the batteries mostly full most of the time for emergency backup.
Connecting as much as I can to my inverter output is the logical place my brain went but my inverter & battery bank are in the basement, while my home office (with a small window ac) is on the second floor. Running wires and extension cords up two flights of stairs will be a no go with the wife ha! How do you connect everything to your inverter output without a mess of wires everywhere or is everything in close proximity to your inverter?
If you are able/willing, I'd love to see some photos of your set up.

 

[Coil]

I've since changed some things around since I took this but this is the gist of it. The PV wires are coming through the wall just off camera there and the AC input is coming from the bottom right. The AC output is actually on a 3 way 12 gauge splitter now so there's a second cord that goes over to the window unit and a chest freezer on the right. That leaves me with one more outlet if I need to run a cord upstairs to the fridge during an outage or something. The battery is on the bottom shelf there.

One of the really nice things about this for me is that since my modem, router, and server are all hooked up here I usually still have internet in the event of a power outage and I can still access my local network and z-wave devices and such through home assistant. Brief power outages of a few seconds are very common for me and this saves me a lot of headaches of restarting a bunch of VMs and stuff. Also helps protect the hardware from sudden power loss.

There are also several graphics cards mining ethereum in there so that helps use up the power.

This area is definitely not the most sensible for a window AC unit being an unfinished corner of the basement but I figure as long as I'm generating the power I may as well use it.

As a bonus, I have the inverter's RS232 cable running to that server so I can feed the data from the inverter out and monitor it remotely.

I'm also going to add some PoE security cameras to feed off the inverter output which will involve me running ethernet to some new places but means my security won't go out in an outage either.

 

[Yankeroo]

Very nice! Maybe my solution here is to just move more stuff into the basement....
or here's an idea, disconnect the circuit to my home office from my main panel and connect that wiring directly to the inverter output...is that crazy?

 

[Coil]

Since at that point you would be dealing with house wiring you might end up with some insurance issues if something caught on fire. It really depends on your local regulations and building codes and permit requirements.

A big part of the reason I don't really sweat not using all of my power (because even with all that I don't) is that my power costs 11 cents/kWh. So how much trouble am I really willing to go to save maybe $10-15/month.

For me, it's enough to be the only wifi network in suburbia during an outage

 

[Yankeroo]

Similar threads​

Setting aside for a moment the fact these are not UL listed and should not be grid tied in in the USA:

That is exactly how they work. I split a 12 gauge extension cord and wired one end to the AC output where I plug in the loads and the other goes into the wall for drawing grid power when needed. Yes, you could turn on the grid tie and it would back feed but it's entirely likely you would be breaching the appropriate upper voltage limits on that breaker at times of high production. But yes, you could.

Started reading through the various setting on these inverters and came across setting 3, 'output voltage'.
The description of each option starts out with "If selected, acceptable feed-in grid voltage range will be ...... "
The wording seems odd here, is this referring to the voltage that will be sent back into the grip, or voltage from the grid into the active load/charge the battery?

 

[Coil]

Mine is set to 120v. What I think it's saying is "this is the voltage range the inverter will acceptably output while feeding back in to the grid". If you look on page 28 of the manual you will see that the volt/amp combinations for each of the three voltages is listed under the grid output section of the specifications table.

I believe this is also the range within which the inverter will "believe" that grid is still active and will suspend grid-tie feeding if the voltage falls outside those.

I think 120 is the right choice since it most closely matches the North American voltage tolerance range (https://voltage-disturbance.com/voltage-quality/voltage-tolerance-standard-ansi-c84-1/)

This does change the target output voltage even if you aren't grid feeding (so if you had no AC input you could output about ~110 volts). I'm not sure what the point of that would be and I'm honestly not sure what the point of this setting really is.

 

[Cheap 4-life]

I am looking at a few hybrid inverters from MPP and Growatt and I'm curious if they can pull the excess load from the grid when the solar is not sufficient for a load. I.E. if I am making 600w but my load is 1000w will the excess be pulled from the grid or do they just switch to grid power entirely. I'm currently using a grid tie inverter with a limiter that measures the power draw and never puts back in more than I am using, but a hybrid inverter, assuming it does what I mentioned it could accomplish the same and more as I could also use it for charging my batteries and inverting. I recently upgraded from 400w to 1200w of solar panels and have to upgrade some equipment and I'm thinking a hybrid solar inverter might be my best option so I can replace separate inverter, MPPT controller, grid tie inverter (with limiter) and battery charger.

There is only very few inverters that can use a low voltage battery and limit its production to only what the loads are using and at the same time allow the grid to supply any access power the main panels loads need. Mpp or growatt cannot do all of that. I am also using grid tie inverters with limiters so your question is one that I have dived into.
Outback skybox, Schneider, and SolArk/Deye are the only inverters (I know of) that can do what you ask. They are the only all in ones that can use external CTs like the battery powered grid tie inverters with limiters can to limit their production to only the amount of load your main panel is using. Unfortunately they are way more expensive than the battery powered grid tie inverters with limiters. Only thing the grid tie inverters with limiters can’t do (for your purpose) that those all in ones can do is power loads when the grids down. For that I have a separate small offgrid inverter for essential loads.

 

[Coil]

There is only very few inverters that can use a low voltage battery and limit its production to only what the loads are using and at the same time allow the grid to supply any access power the main panels loads need. Mpp or growatt cannot do all of that. I am also using grid tie inverters with limiters so your question is one that I have dived into.
Outback skybox, Schneider, and SolArk/Deye are the only inverters (I know of) that can do what you ask. They are the only all in ones that can use external CTs like the battery powered grid tie inverters with limiters can to limit their production to only the amount of load your main panel is using. Unfortunately they are way more expensive than the battery powered grid tie inverters with limiters. Only thing the grid tie inverters with limiters can’t do (for your purpose) that those all in ones can do is power loads when the grids down. For that I have a separate small offgrid inverter for essential loads.

You seem to be talking about combining battery power and utility which you correctly point out the MPP and growatt will not do. His question though was about combining solar and utility which they absolutely will do. For the MPP at least the options are

• solar and utility at the same time (fall back to solar + battery)
• solar and battery at the same time (fall back to utility ONLY)

 

[Yankeroo]

Mine is set to 120v. What I think it's saying is "this is the voltage range the inverter will acceptably output while feeding back in to the grid". If you look on page 28 of the manual you will see that the volt/amp combinations for each of the three voltages is listed under the grid output section of the specifications table.

I believe this is also the range within which the inverter will "believe" that grid is still active and will suspend grid-tie feeding if the voltage falls outside those.

I think 120 is the right choice since it most closely matches the North American voltage tolerance range (https://voltage-disturbance.com/voltage-quality/voltage-tolerance-standard-ansi-c84-1/)

This does change the target output voltage even if you aren't grid feeding (so if you had no AC input you could output about ~110 volts). I'm not sure what the point of that would be and I'm honestly not sure what the point of this setting really is.

It would seem that the point of the setting is to prevent the backfeed to the grid from exceeding the voltage rate of the breakers?

 

[Coil]

Apparently this inverter would also work in Japan using 101 volts at 50 hz so I think it's just a regional compatibility thing.

 

[Cheap 4-life]

You seem to be talking about combining battery power and utility which you correctly point out the MPP and growatt will not do. His question though was about combining solar and utility which they absolutely will do. For the MPP at least the options are

• solar and utility at the same time (fall back to solar + battery)
• solar and battery at the same time (fall back to utility ONLY)

The op said he’s currently using grid tie limiting inverters. The growatt and mpp do not have the functionality to do limiting via external CTs like his current inverter

 

[Capt Bill]

I am looking at a few hybrid inverters from MPP and Growatt and I'm curious if they can pull the excess load from the grid when the solar is not sufficient for a load. I.E. if I am making 600w but my load is 1000w will the excess be pulled from the grid or do they just switch to grid power entirely. I'm currently using a grid tie inverter with a limiter that measures the power draw and never puts back in more than I am using, but a hybrid inverter, assuming it does what I mentioned it could accomplish the same and more as I could also use it for charging my batteries and inverting. I recently upgraded from 400w to 1200w of solar panels and have to upgrade some equipment and I'm thinking a hybrid solar inverter might be my best option so I can replace separate inverter, MPPT controller, grid tie inverter (with limiter) and battery charger.

I have a few MPP LV2424 (green) Hybrid models networked together for 240vac split phase output (set up in kind of isolated island mode); getting up to about 20 amps 120vac output from each unit when fully solar powered with my 2K+ Watts of Solar per unit. They have over 25 configuration options to play with ... & learn about. I like em, including for having my home grid power be backup on all the loads on my Lv2424 powered circuit breaker box. I have my home grid supply automatically going through my LV2424 unit at night, plus for day time loads above what solar panels are supplying. ... Lots of options to go through a learning curve. ... Which ever way you go, I suggest downloading the manual, and printing out the configuration options; to study em . I used sticky tape on the unit metal faces of my LV2424s to record conf # w some of the more important configuration options I was switching around; to test em; for better understanding em; ... to then fine tune em to get what I want. The LV2424 Hybrids need an additional card to network em in multiples. They can also feed power to the grid, but won't make the legal hoop jumps in California for Grid Tie power feeds (likely same story in all of USA, but I don't know that for sure). IMO: Experimenting with Grid Feeding could mean big problems with one's grid supplier) ... Some folk might figure out grid feeding on old mechanic power meter type grid supply (grid feed will turn em backwards), especially outside the USA, or maybe gorilla style? and maybe with a power limiter. I hear it is Bad to give back a surplus to grid supplier at end of month meter reads/ and some say Bad to supply grid feed surplus even for a minute.
Re : GroWatt. Lots of options/ seen 10 year warranty on some units in my study of data sheets (specs). I imagine many could pass grid through unit as backup to loads, but would have to study more to know the specifics of the model I was considering.