SolarEdge battery settings help / reality check

So I don't have a SolarEdge battery, but I do have a Powerwall. I think I get your desired scenario, let me see if I understand correctly. But first, what is your utilization at Peak TOU? As in, how many kWh do you use in that time period?

So for the Powerwall, there are two modes: Self-Powered and Time-Based Control. And then you have your Backup Reserve percentage.

For Self-Powered, the battery starts discharging when the solar output can no longer keep up with the load. It supplements the solar for whatever the deficit is. For me, when I was on Self-Powered for a couple weeks in August, my solar would generate credits into On-Peak until around 5:30pm, that's about when it couldn't keep up with the AC. I believe I had the reserve set at 20%. Since my AC would go constantly for a few hours, I would go fully on-grid around 1am. Then as the sun came up excess solar would be sent to the Powerwall until it was charged up at around 11am, then excess solar would be sent to the grid until again around 5:30pm, rinse and repeat. So that day I pulled only 5.6 kWh from the grid, most of it at Super Off-Peak. I would charge my EV during the day under solar. Here's an example:



Now for TOU, the battery kicks in at 4pm and sends all solar to the grid during On-Peak for maximum credits. In this example you'll see me running my battery down to 20% but everything On-Peak went to the grid, and you'll see I charged my EV at midnight earlier that day at Super Off-Peak.



So if I'm getting this correctly, you want more of the first scenario? The self-powered one?

Thanks OCJ.

Yes, I am thinking the self-powered scenario you described. For sake of example, let's say I have 4kWh battery power available on a clear, not-too-hot, August evening. Solar generally covers 4-5 pm, mix of solar and battery 5-6 pm, all battery after 6 pm. I would expect the 4kWh to last me through 9 pm in my desired scenario.

Instead, in my current less desired scenario, starting at 4 pm, solar and battery combine to power the house and export ~4 kWh to the grid and the battery exhausts before 6 pm.

Perhaps I am not understanding this fundamental part of residential solar with batteries: Isn't it better to avoid import altogether instead of exporting for the energy credits only to have to import that amount of energy later in the same ToU period?

This does not compute, LOL. Here AC is fully blasting and with house load will eat up that 4 kWh in about an hour and a half.

So all this depends on what your actual load pattern looks like. Above you can see my baseline at 4pm is around 500W, with peaks of around 2.7 kW as my AC cycles. Yesterday my usage was 8kWh between 4pm and 9pm, of which 7.9kWh came from my Powerwall, 0.1kWh came from the grid, and 7.0kWh was sent to the grid at On-Peak rates.

So it sounds like you are on TOU programming. Which is actually where you want to be (if you're in SoCal). Self-Powered minimizes send to the grid and denies the utility the ability to re-sell your kWh, but it also denies you that load shifting ability of being able to generate credits at On-Peak and use them at Off-Peak or Super Off-Peak.

I have not done the numbers on your scenario, where you are exporting and importing at the same TOU period. My battery gets me completely through TOU. I'll have to think about that. But you have 9.7 kWh in battery so really you should be using that all up on On-Peak and load shifting. In SoCal, you do get hit with some NBCs but with net metering and the different plans available, you still come out ahead. Remember it's the differential between On-Peak and Off-Peak that you are taking advantage of.

Just to complicate things even further, I'm looking at generating about $1k in credits with TOU, then maybe switching from battery TOU to Self-Powered for a while. The idea is to have that buffer in case my system goes down for a month or two, I'm not going to end up net owing at my True-Up. There are all kinds of ways to slice and dice this.

I'm in the SF Bay Area, so with window management we can avoid a lot of AC in the evening We usually PV export 4-5 pm then use ~3.5-4.5 kW from 5-9 pm. The scenario that you describe is what I expected--where the battery powers you through the bulk of the ToU period. Thanks for the reality check! But something is amiss with my system. I guess I am going to have to live with it for now.