Tesla Powerwall not charging from solar panels
Your solar panels are generating but the Powerwall stays at the same percentage — or the Tesla app shows 0kW from solar when the inverter is clearly running. This is usually a CT clamp orientation issue, a wrong operating mode, or a Gateway metering fault. This guide covers Powerwall 2 and Powerwall 3.
Tell us your Powerwall model, what the Tesla app shows for solar generation, and how long the issue has been happening. We review app data and Gateway configuration remotely.
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Step-by-step charging fault diagnosis
Work through these steps in order. Step 1 catches the simplest cause — wrong mode. Step 2 addresses the most common hardware cause — reversed CT clamps. Steps 3–5 cover Gateway, inverter, and Powerwall 3 specifics.
Open the Tesla app → Settings → Customize. The mode should be Self-Powered or Time-Based Control. If it is set to Backup Only, the Powerwall reserves capacity exclusively for power cuts and will not charge from solar during normal operation. In Self-Powered mode, the battery charges from any excess solar not used by the house. Also check Energy Exports under Customize — if set to Everything, the system prioritises export over battery charging once full, which is normal. If the battery is not full and still not charging, the mode is not the issue.
CT clamps are directional — the arrow must face toward the source (away from the consumer unit). If the solar CT is backwards, the Gateway reads generation as negative and will not charge the battery. In the Tesla app, check the energy flow diagram: if solar shows 0.0kW when the sun is out and the inverter is running, or shows a negative value, the CT is reversed. The fix is physical — rotate the clamp 180 degrees on the cable. A reversed site CT can also cause the entire power flow to be misread, making it appear that solar exports to grid instead of charging the battery. This requires an electrician.
In the Tesla app, go to the Device page and confirm your solar inverter appears as a recognised device. Then check the Metering page — the Solar CT must be assigned and on the correct phase. If the inverter is not registered, the Gateway does not know solar exists and will not use it to charge the Powerwall. This can happen after a Gateway replacement, a firmware update, or if commissioning was not completed. Re-registration requires installer access to the Gateway commissioning interface.
The Powerwall cannot charge if the solar inverter is faulted or producing nothing. Check the inverter display or its own monitoring app — is it showing active generation? Common faults that prevent generation include grid voltage trips (G98/G99 disconnection in the UK), a tripped AC or DC isolator, or an earth fault. If the inverter is faulted, the Powerwall not charging is a symptom, not the cause — fix the inverter first and the Powerwall will resume charging automatically.
Powerwall 3 charges at a maximum of 5kW per unit from solar or grid, despite having an 11.5kW discharge output. This is a design characteristic of LFP (lithium iron phosphate) chemistry that protects the cells. If your solar array peaks above 5kW, the excess exports to grid even while the Powerwall is not full — this is normal behaviour, not a fault. Two Powerwall 3 units charge at 10kW combined. Powerwall 2 (NMC chemistry) also charges at 5kW per unit. If your system charges slowly but does charge, the rate limit is likely the explanation rather than a fault.
If the mode is correct, CTs are properly oriented, and the inverter is generating — perform a Gateway power cycle. Turn off the Gateway circuit breaker, wait 30 seconds, turn it back on. Allow 5 minutes for the system to reconnect and re-establish communication. Check the Tesla app for pending firmware updates — Tesla pushes updates automatically but they can stall. If the issue persists, the Gateway may have a metering fault or the Powerwall may have a hardware issue. Contact STS for a remote diagnostic — we review your Tesla app data, generation history, and Gateway configuration to determine the next step.
Tesla Powerwall charging — how it works
The Tesla Powerwall charges from solar through the Gateway, which acts as the brain of the system. It monitors solar production via CT clamps, measures house consumption, and decides whether to charge the battery, power the house directly, or export to the grid. The decision depends on the operating mode in the Tesla app: Self-Powered prioritises battery charging from excess solar, Time-Based Control follows a tariff schedule, and Backup Only reserves capacity for power cuts. If any part of this chain breaks — wrong mode, reversed CT, unregistered inverter — the Powerwall appears to ignore solar even though everything else is working.
Powerwall 2 is AC-coupled — solar goes through a separate inverter to AC, then back to DC into the battery, with roughly 7% conversion loss. Powerwall 3 is DC-coupled with a built-in inverter, reducing loss to under 3%. However, Powerwall 3 has a 5kW charge input limit per unit due to its LFP chemistry, which means large solar arrays will always export some energy midday even when the battery is not full. STS diagnoses Powerwall charging faults remotely by reviewing the Tesla app energy history, Gateway metering configuration, and firmware versions. We are independent from Tesla and from your installer.
Powerwall charging — common questions
The most common cause is a CT clamp installed backwards — the Gateway reads solar as negative and won't charge the battery. Check the Tesla app energy flow: if solar shows 0.0kW or negative when the sun is out, the CT orientation is wrong. The second most common cause is the mode being set to Backup Only instead of Self-Powered. Also verify the inverter is registered on the Gateway Device page and is generating.
Powerwall 3 charges at 5kW max per unit from solar or grid, despite 11.5kW discharge output. This is an LFP chemistry design characteristic. Solar above 5kW exports even when the battery isn't full. Two units charge at 10kW combined. Powerwall 2 also charges at 5kW per unit but uses NMC chemistry.
CT clamps have an arrow that must face toward the source — for solar, the arrow points toward the inverter. If reversed, the Gateway reads generation as negative. Check in the Tesla app: watch the energy flow diagram while the sun is out. If solar shows 0.0kW or negative when the inverter is generating, the CT is backwards. The fix is physical — rotate the clamp 180 degrees, which requires an electrician.
No — they cannot be installed together. Different battery chemistries (NMC vs LFP), different firmware, different Gateway generations. Powerwall 2 is AC-coupled with a separate inverter; Powerwall 3 is DC-coupled with a built-in inverter. Add another unit of the same type if you need more storage — up to 10 Powerwall 2 units or 4 Powerwall 3 units per system.
If the battery is full, exporting is normal. If it's not full: check the mode (Backup Only won't charge from solar), check Permission to Export under Customize, and check for a backwards CT clamp causing the Gateway to misread power flow. On Powerwall 3, solar above the 5kW charge limit exports even when the battery isn't full — this is by design, not a fault.
Powerwall still not charging?
If you have checked the mode, CT orientation, and inverter — and the Powerwall still will not charge from solar — the issue may be a Gateway metering fault, a firmware bug, or a Powerwall hardware problem. We review your Tesla app data, energy history, and Gateway configuration remotely. Independent from Tesla and your installer.