General hybrid inverter questions

[chilly2]

Hello,

In interested in adding a hybrid / all in one inverter to my home. My concern is that the array / batteries will not be able to high load situations, therefore I'm looking for a system that can make up the shortfall with grid power e.g. early morning with PV still charging battery, cloudy days, etc.

• Is grid assist functionality even a thing?
• Does anyone have recommendations on reliable equipment that can do this?
• Is load thus throttled by the inverter limit or will grid assist allow whatever is needed by loads?

Details:

• Location is the USA, so need to be able to provide 120v/240v.
• The reason for the hybrid is so there is zero chance of export back to the grid.
• I do not have Sol-ark levels of cash available.

Advice gratefully appreciated.

 

[rpdom]

I have a hybrid inverter (Solis S5-EH1-3K-L). I'm UK based, so things will be slightly different to you in the US.

What you call "grid assist" is the default of how my hybrid works. The inverter connects to the incoming grid, after the utility meter. It tries to supply enough power (from PV and batteries) to that so the amount coming in through the meter is zero. When the load exceeds what the inverter can supply, the rest just comes from the grid. A meter and CT on the grid supply allows the inverter to measure the import/export level so it can adjust its output.

For example, my inverter has a maximum AC output of 3kW. I have an 8.5kW electric shower. When running flat out the inverter will supply 3kW and the remaining 5.5kW will come from the grid.

Hybrids do/can still export to the grid. Priority for PV generated power is firstly the load, then any surplus goes to charging batteries, if needed, and the rest is either exported or, if export is restricted, the inverter will throttle back its inputs.

Solis are more common in UK/EU, but there are US models. They are fairly cheap and appear to be reliable.

 

[DIYrich]

Off-grid inverter should work. Connect grid to generator input. The inverter will take what it needs to support load from the Gen input.

Hybrid should also work in Grid Zero mode (no export).

 

[RCinFLA]

Victron, Schieder, and Outback units can do AC input assist. Also called 'load shaving'.

Victron has 'dynamic' assist which starts to do inverter supplementing when AC current rate rises quickly. This is supposed to help for startup surge loads by not waiting to hit supplement trigger limit set for supplementing. It drops back supplementing after surge, assuming AC output is still below supplementing set input level.

For load shaving, there are various added features like Time of Use settings to engage during certain periods of day. This is intended for time of use utility tariffing rate situations where you get lower utility rates during off peak demand time.

 

[Alex1]

I use ea sun SMG II 3.6kw half year, plan was to use it without batteries but...
When I was using high load output 3kw (from PV 2.8kw and grid 200W), when i cut off load, for some short period time i got grid exported peak power 2kw, inverter cant instantly reduce power, is it just me with this problem? In week I got ~6Wh exported, as i can see in shelly AP.
I dont like that at all.

I add batteries, 280Ah.
Now i dont have grid export, but i see that inverter too slow reacts for power damand.
If there is full battery, power from PV only 500W (current load in house), when consumption increases instant to 3kw, first pulls from the battery 2.5kw1-2s, and than power from PV grows to the highest possible..
Best situation is when battery charging is in progress. then PV power kick in instant reducing battery charging...
is this normal, or just cheap inverter...

 

[1201]

Off-grid inverter should work. Connect grid to generator input. The inverter will take what it needs to support load from the Gen input.

Hybrid should also work in Grid Zero mode (no export).

I don't believe this is how most of grid inverters work

 

[RCinFLA]

Most low cost HF inverter do not have AC input assist. Cheaper LF inverters do not have the AC input current measurements to control AC input assist. On cheap inverters, AC pass-through current from AC input to AC output is unsupervised and uncontrolled by inverter.

If you don't see an item in user setting that relates to limiting AC input current the unit does not have AC input assist. Xantrex changed their user setting parameter name for AC assist to 'AC input breaker amperage', a rather obscure change of name IMO.