diy solar

diy solar

Mixing Hybrid and On-Grid


May 7, 2024
I am looking to setup one grid-tied (5kw) and one hybrid (5kw) inverter in the same house due to cost concerns. Each inverter has its own 5kw solar panels.

Is this possible at all?

And is it possible to export the excess energy from both of these?

Separately, these both inverters can, but I am not sure how to have both in the same house and to export from both of these. Anyone know of a diagram of how such a setup could be done?
What is your definition of Grid Tied and Hybrid? (I don't like the term Grid Tied because it means different things to different people)

Since you are saying both can export, I assume the grid tied is either a string inverter or a micro inverter (Micro Inverters should be called micro-string inverters).

Assuming we are talking about a string inverter and a hybrid inverter, there are multiple ways of doing it.

If the objective is to have them both charge the batteries when the grid is down, the hybrid should be the primary and control the string inverter. This is done a couple of different ways with hybrids: Some use a special port for connecting the string inverter, others connect the sting inverter to the load port.

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you can have two different inverters which both export to grid. Sum of current from both flow out, and neither knows about the other any more than two appliances know about each other. Unless one uses CT, current transformers, to measure grid current.

As FilterGuy indicates, you may also be able to have grid-tied inverter connected to output (or generator) port of hybrid, so its power is available off-grid. Depends on models and features.

How you tie the AC together, e.g. breakers in your main breaker panel vs. line-side tap between meter and breaker panel or other method determines how much total current is allowed.

Is it not feasible to use a single 10kW or 11.5kW hybrid?
A larger hybrid inverter will be better able to start motor loads. Motors draw about 5x their rated power for a couple seconds at startup. You will not get this feature with separate grid-tie inverter, only with larger hybrid inverter.
What is your definition of Grid Tied and Hybrid? (I don't like the term Grid Tied because it means different things to different people)
Sorry I wasn't too clear on terminology, but I believe it's string since it's for a home setup using the common residential solar inverters.

And thanks for the diagram.

I am looking for a setup as this (each separate, but the power meter / grid is the same)

1. 5KW Hybrid inverter with 5KW solar panels (export + battery backup). This will be connected to my load.
2. 5KW On-Grid / Grid-Tied inverter with 5KW solar panels: mainly for the purpose of export. It's lucrative in my country to export to grid. It doesn't have to be connected to hybrid in any way. Only purpose is to feed to the grid.

We have power failures in my area on daily basis so the hybrid is required too.

I hope I am making sense and sorry for the lack of correct terms.
Do you already have the 5kW grid-tie inverter?

If not, consider a 10kW (or some are 11.5kW) hybrid/all in one.
If so, consider a hybrid that can AC couple with the grid-tie inverter. That would make its power available during backup operation.

In the US, newer inverters have "Rule-21" frequency-watts. If the grid, or a hybrid inverter, raises line frequency, then the grid tie inverter ramps down output power. Other countries may not require that, but some inverters were designed for AC coupling off-grid and support it.

A US model hybrid Sol-Ark supports AC coupling through its "Gen" relay, which allows it to switch off the connection, rather than using frequency shift. Possibly a related brand Deye offers similar operation in your market. That way it doesn't matter whether grid-tie inverter supports frequency-watts or not.

With the SolArk, we would put 5kW of PV panels on its DC coupled PV input. We would put 5kW of AC coupled grid-tie inverter on its Gen input.
SolArk would then have 10kW of PV available for AC loads and battery charging.
As power need decreased, SolArk would ramp down power from DC coupled PV, 5kW down to zero.
For further decrease, it would disconnect 5kW of AC coupled grid-tie inverter and raise DC coupled PV back up to 5kW ... 0kW as needed.

So long as DC coupled PV is equal to or greater than AC coupled PV, you get zero to 10kW of power, continuously variable.

Alternatively, just do what you originally proposed.
5kW of AC coupled grid-tie PV.
5kW of hybrid PV-battery system for backup.
You can let that export 10kW to grid. or, if only allowed 5kW, use CT so hybrid senses what consumption by loads and what export from grid-tie PV. It can then export just enough to sit at 5kW.
Do you already have the 5kW grid-tie inverter?

Thanks for the response.

Yes I have already bought 5kw grid-tie inverter along with the solar panels and all the structure. It isn't fully setup yet but the 5kw string has been installed already.

The 5kw grid-tie inverter:

However, I realized later it won't work at times of power failures. So I changed the plan the plan to add in a 5kw hybrid inverter with another set of 4-5kw panels and batteries as well.

Alternatively, just do what you originally proposed.
5kW of AC coupled grid-tie PV.
5kW of hybrid PV-battery system for backup.
You can let that export 10kW to grid

This would be ideal in my situation I believe. And yes, I would like to export as much as possible / excess from both the inverters.

Are you aware of any guide or reference for such a setup? Or perhaps the correct keywords I should be googling for?

Thanks again.
If you just want to export excess whenever it is produced (don't have to deal with time of use and different import/export rates), just connect each system without regards to the other. They won't even know each other exist.

Is this 230V? 10kW is about 40A. Is your grid connection and electrical panel able to handle that?
We have a few rules when backfeeding a breaker panel, making extra current available to loads in addition to what main breaker supplies from grid. The idea is to avoid putting say 100A + 40A = 140A through a 100A busbar. There are ways to avoid that happening.

Is 5kW x 6 hours = 30 kWh/day enough for your backup loads? Or would you like to make the other 5kW available?
That's why I suggested seeing if Deye or some other hybrid could AC couple.

Or, buy a 10kW hybrid, put all the panels on it, sell the grid-tie inverter or save it as a spare, in case hybrid stops working.
One 10kW hybrid may be the cheapest and simplest.

If one 5kW array is oriented East and one oriented West, you get more hours of production but less peak power, less peak current. That would fit on a smaller inverter and be less current through the breaker panel. 10kW (STC) of PV panels is probably about 7.5kW peak power actually produced, except on cool days.

The two orientations is also a better fit for off-grid operation, makes power while you're using it instead of a high peak at Noon.