Home batteries

Battery discharging to grid unexpectedly

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

Your battery is full or has a high percentage, but instead of powering your house, your monitoring app shows power flowing from the battery to the national grid. This often happens even when you have high demand in the house (like the oven or kettle being on).

What’s normal vs not normal

Normal:

Force Export: You have deliberately set a “Force Export” schedule to sell power during a peak-price window (e.g. on Octopus Flux or Agile).
Maintenance Cycle: The battery management system (BMS) is doing a “re-calibration” of the cells, which may involve a full discharge.

Not normal:

The battery exporting to the grid while you are also importing from the grid.
The battery exporting during a time when export prices are very low or zero.
Exporting when the battery is already near its minimum safe percentage (e.g. 10%).

Likely causes (ranked)

CT Clamp installed backwards: The sensor that tells the battery which way the power is flowing is facing the wrong direction, making the battery think it’s importing when it’s actually exporting.
Incorrect Mode: The inverter is set to “Timed Discharge” or “Feed-in Priority” instead of “Self-Consumption” or “General Mode.”
Third-party App Conflict: An external optimization app (like Octopus Intelligent or a smart home integration) is overriding your local settings.
Meter Calibration: The internal power meter in the inverter has lost its calibration and is miscalculating the house load.
Faulty Communication: The communication cable (RS485/CAN) between the smart meter and the inverter is damaged or disconnected.

Quick checks you can do safely

Check the Mode: Open your battery app and ensure it is set to “Self-Consumption” (or your brand’s equivalent).
Check the Schedules: Look for any “Force Export” or “Timed Discharge” schedules that might be active in the app.
The ‘Kettle Test’: Turn on a high-power appliance (like a kettle). Does the export to the grid stop and the battery start powering the house? If not, it’s likely a sensor issue.
Check the CT Clamp: If you can safely access your meter cupboard, look for a small clip around your main incoming cable. Is it closed properly? Is the arrow pointing toward the house?

When to call an installer

If the “Kettle Test” fails and the battery continues to export regardless of house load.
If your app shows a “Meter Comm Error” or “CT Fault.”
If you suspect the CT clamp has been installed in the wrong location (it must be before any solar/battery connections).

Questions to ask your installer

“Is the CT clamp arrow facing the correct way (toward the consumer unit)?”
“Is the ‘External Meter’ or ‘Internal Meter’ setting correctly configured in the inverter software?”
“Does the communication cable between the meter and inverter need a shielded replacement to prevent interference?”

FAQs

Is exporting bad? Not if you are being paid for it! However, if you are on a standard tariff, you are usually better off using that power yourself later in the evening. What is ‘Self-Consumption’? This is the default setting for most home batteries. It tells the battery to only discharge when your house needs power and to only charge when you have “spare” solar power. Can I stop it remotely? Yes, most apps allow you to change the operating mode instantly. If it’s exporting unexpectedly, try toggling the mode to “Idle” or “Stop” while you investigate. Will it damage the battery? No, but it’s an inefficient use of the system’s cycles. Every time you discharge to the grid and then have to buy that power back later, you are losing money. Why does it happen at night? If it’s exporting at night, you almost certainly have a “Timed Discharge” schedule active or a faulty CT clamp that thinks you have solar generation occurring.\n

Written by NetZeroNow | Last updated on 2026-03-02

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