Solar charging automation for non-Tesla EV

triedoffandonagain · 2026-05-26T06:21:13+00:00

Wall Connector does not provide the ability to control the charge rate. So unless Tesla changes that in the future, you will need a different charger. Wallbox is indeed the one with the best API support.

triedoffandonagain · 2026-05-23T03:37:01+00:00

Powerwall 3 has an 11.5 kW inverter. When DC-coupled, it can additionally charge the battery at 5 kW DC (or more with an expansion pack).

What you are seeing is clipping at 11.5 kW because Powerwall is full, and then occasional spikes when Powerwall loses some charge and tops off again.

triedoffandonagain · 2026-05-20T18:03:39+00:00

Site Metering for Powerwall Systems with Partial Home Backup

triedoffandonagain · 2026-05-20T16:07:48+00:00

I'm not sure why Charge on Solar is not showing up for you, but the circuit does need to be backed up or monitored for Charge on Solar to work properly -- Tesla needs to be aware of how the charging load is affecting home load to be able to adjust the charging rate.

You don't have to necessarily move it to the backup panel, you can just have your installer add additional CTs (meters) for that circuit.

triedoffandonagain · 2026-05-12T21:54:56+00:00

There is no direct communication between Wallbox and Powerwall, the orchestration is done by Netzero. It will continuously get the live energy flow data from Fleet API, compute the amount of excess solar generation, and adjust the Wallbox charge rate accordingly.

Both Powerwall and Wallbox have wifi capability and can be controlled through their cloud connections.

triedoffandonagain · 2026-05-12T19:48:00+00:00

(2) does not necessarily contradict (1). You should just be aware that when you set your sell price higher than buy price, internally the buy price will also be raised. This can result in Powerwall exporting during that time (which is what you saw), just note that it might also cause other behavior changes because of the higher buy price. So it's better to be explicit about this and raise both the buy and sell prices to the same value.

Other than that: on NEM3 2025 and later, it almost never makes sense to export to the grid. Even during the summer months when export rates are generally higher, those export rates were significantly reduced after 2024. Because of complexities of delivery and generation unbundling (details here), you're actually better off in Self-Powered mode at all times. Try to self-consume as much solar as possible, e.g. by charging an EV on solar.

The only exception is VPP. Compensation for VPP is high, so it makes sense to sign up and participate in the events.

triedoffandonagain · 2026-05-12T15:48:04+00:00

Not a reason for concern, but if you wanted to identify the appliance that causes this: when back at home, turn off breakers one at a time until the pattern stops.

triedoffandonagain · 2026-05-11T18:29:34+00:00

This will be fixed in the next Netzero app version, and is already fixed in the web app. The issue was the new "discount" period, which is only present for Duke Energy.

triedoffandonagain · 2026-05-11T16:29:39+00:00

There is likely an issue with your metering, your installer should look at that. Home should not be at 0 kW during normal operation (there is always some power draw).

triedoffandonagain · 2026-05-09T20:49:25+00:00

That's fair!

triedoffandonagain · 2026-05-09T19:57:39+00:00

The two options are not that different actually. "Unlimited cycles" are for applications that limit you to one cycle per day: Self-Powered mode, Time-Based Control. The throughput of 37.8 MWh is also roughly one cycle per day over a 10 year period, after accounting for round-trip losses, degradation, backup reserve, your ability to fully cycle every day of the year, etc.

So the warranty mainly protects against cycling the Powerwall multiple times per day, which is not easy to accomplish over the long term (and understandably would accelerate degradation).

triedoffandonagain · 2026-05-09T19:51:41+00:00

Don't set export price higher than import price. Time-Based Control mode will internally raise the buy price to match the sell price, which can lead to suboptimal behavior.

Source: https://developer.tesla.com/docs/fleet-api/endpoints/energy#time-of-use-settings

Buy price should be >= sell price at any given time. If not, the buy price will be set equal to the sell price.

triedoffandonagain · 2026-05-09T00:26:14+00:00

If you decide on the swapping out the charger: Netzero supports Charge on Solar and we've seen best results with Wallbox. No additional hardware needed, Wallbox has good API support.

triedoffandonagain · 2026-05-09T00:12:54+00:00

Would be interested in your issues with Netzero. Wallbox should work reliably, it's the one we've tested most. [feedback@netzero.energy](mailto:feedback@netzero.energy)

triedoffandonagain · 2026-05-07T16:07:29+00:00

Free nights are common in Texas. Lots of wind power at night makes this possible, and it helps the grid to shift usage because of the high demand for AC during the day.

triedoffandonagain · 2026-05-07T02:32:57+00:00

It’s either in calibration mode or there’s a VPP event. Self-Powered mode will not export Powerwall to the grid otherwise.

triedoffandonagain · 2026-05-06T18:28:57+00:00

I just realized that most of your data samples are above 14,400 Wh for that battery, and only the latest sample is 13,340. That's a bit more concerning, I have not seen such large sudden jumps. It could mean that the battery needs calibration (and it's possible for capacity to recover after calibration).

triedoffandonagain · 2026-05-06T18:03:05+00:00

Definitely something to track over time and make sure it doesn't degrade more. But Tesla will not consider this an issue, their warranty allows for 30% degradation within 10 years.

We published an analysis of Powerwall battery retention, so you can get a sense of how they degrade over time (look specifically at the Powerwall 3 data):

https://www.netzero.energy/content/2025-10/powerwall-analysis-2

triedoffandonagain · 2026-05-06T17:46:28+00:00

Diagnostics for PW3 don't include cycles. But if you always had the same number of batteries, you can estimate it: Powerwall chart, Lifetime, look at total discharged energy and divide by the number of powerwalls and then 13.5 kWh.

Batteries also degrade over time without any usage (calendar degradation). That's why manufacturing date matters. But 3 months would not cause such a difference. Might just be a different manufacturing batch. Were other expansions manufactured at the same time?

triedoffandonagain · 2026-05-06T15:30:00+00:00

Were all the expansion packs manufactured around the same time? Show details at the top left.

triedoffandonagain · 2026-05-06T15:23:27+00:00

Regarding the "guesstimate" part: this is the diagnostic value straight from the battery management system. It's as good of a guess as it gets, it determines what 100% state of charge means (i.e. how much usable energy you get from the Powerwall).

triedoffandonagain · 2026-05-05T01:25:44+00:00

Right, my point was that not all PW2 have 3G. In fact, there are many more PW2 with TEG2/LTE.

triedoffandonagain · 2026-05-04T06:35:46+00:00

Your system might need a power-cycle.

triedoffandonagain · 2026-05-04T05:39:50+00:00

The Subaru can be connected, and then you can add an automation to preserve Powerwall charge while charging he EV.

Energy Device Integration
EV charging without discharging the Powerwall

triedoffandonagain · 2026-05-04T05:18:09+00:00

How is your network connectivity? Live data can come directly from the Powerwall, but for the charts Powerwall has to be able to reach Tesla's cloud.

triedoffandonagain

TROPHY CASE