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Does a Grid-Tied inverter supplement the PV input?

desiresolar

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Jun 15, 2022
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Hello all. Newbie here. I've been watching a lot of YT videos recently from 'DIY Solar Power with Will Prowse'. In a recent video, he showcased an inverter with AC input. That got me wondering if it's possible to run a PV setup without batteries*? The theory is that if there's enough sunlight, the inverter uses that juice first and if clouds roll in, the inverter supplements with the grid to run the load. Is this the case with these inverters?

Goal: Run a small AC window unit in the office to offset electrical costs of whole-house AC just to cool down the office.

(*) The reason for the no batteries ask is basically the additional cost. If I'm already spending $1500 on an inverter, and another $1000 on panels, I don't want to add another $2-4K on batteries if I don't need to because that just delays the cost payback period even more. (I pay $0.10/kwh). Now, I've read some other posts here that say I should get one anyways just to handle the minor drops in watts as clouds drift in/out, so I think I could handle 2-4 car batteries wired up if that helps.
 
Some All-in-One Inverters can be operated without batteries but the output based on solar is unstable. As you mentioned its better to have at least minimal battery back up to help even things out.

You asked: "the inverter supplements with the grid to run the load. Is this the case with these inverters?" Typically they don't work quite in that manner. The Inverter can be set to prioritize the use of Solar & Battery as first and second choices. The grid then becomes the 3rd choice and usually only gets used to charge batteries after the batteries have run down to the low voltage or low SoC setting. The Inverter can also be set up to use Grid as a priority but then it usually goes into pass-thru mode.

For clarification, the more advanced UL1741SA grid interactive inverters that have a feature called Peak Load Shave can be configured to use grid power in the manner you described above in your question. That's an entirely different subject.
 
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