Why did ZEB not charge to 100%?
ZEB may not charge to 100% when it is already highly charged, is responding to calls for heat, or is following its smart charging strategy based on your usage, tariff, and comfort settings.
Use this article to:
- Understand why your ZEB did not reach 100% charge
- Learn how high state of charge and calls for heat affect charging
- See when this behaviour is normal and when it might indicate an issue
Why ZEB may not charge to 100%
ZEB does not always aim to charge to 100%. Instead, it charges to the level it predicts you will need, while also protecting the system and managing charging safely when it is already highly charged.
There are three main reasons your ZEB may not reach 100%:
1. ZEB is already at a high state of charge
When ZEB is already highly charged and actively responding to calls for heat from your heating controls, charging is limited to protect the system:
- If ZEB is fully charged or above 62.5% (~25 kWh) while discharging, it will not continue to charge.
- This affects all types of charging – scheduled (Smart, Basic, Custom) and Boost Charge.
- In this situation, it is normal for ZEB not to reach or stay at 100%, even if a charging window or Boost has been requested.
2. Predicted demand and smart charging
ZEB uses your settings and historic usage to decide how much energy to store:
- If ZEB predicts you don’t need a full core (e.g. mild weather or low heating/hot water demand), it may stop charging at a level below 100%.
- When using Smart Charging with time‑of‑use or off‑peak tariffs, ZEB aims to charge enough to meet your expected demand during cheaper periods, not simply fill to 100%.
3. Recent Boost or previous charging
If you have recently:
- Used Boost Charge, or
- Had a long or very effective charging period,
then ZEB may already have enough energy stored. In this case, it will limit further charging and may not return to 100%, even if you expect it to.