Feature · 3 min read
Usable vs Total Battery Capacity Explained
Why a '64 kWh' battery gives the driver slightly less than 64 kWh.
What's the difference?
Total (or 'gross') capacity is the full amount of energy the cells can physically hold. Usable (or 'net') capacity is what the car actually lets you use day to day. The two numbers are never the same — manufacturers always hold a small buffer back.
How does it work?
Charging a battery to 100% or draining it to 0% repeatedly wears the cells out much faster. To protect the pack, the car's software refuses to charge above a hidden upper limit and refuses to discharge below a hidden lower limit. The buffer at the top and bottom is invisible to you — the dashboard simply shows 0–100% within the usable range.
What does it feel like?
A car advertised as having a 64 kWh battery might actually have 67 kWh of cells, with around 3 kWh held back. So 100% on the dashboard corresponds to about 64 kWh of energy you can actually use to drive.
Benefits of the buffer
- ✓Longer battery life over the years
- ✓More consistent range as the car ages
- ✓Reduces risk of damage from accidental full charges or full discharges
- ✓Allows the manufacturer to back a long battery warranty
Limitations
The headline 'kWh' figure in adverts can be either total or usable depending on the brand, which makes comparing cars confusing. Always check both numbers in the technical spec, and use the usable figure when working out real-world range.
Common problems
- ✓Confusion when two cars with the same 'kWh' have different ranges
- ✓Buffer size shrinks slightly as the battery ages
- ✓Aftermarket 'unlocks' of the buffer void the warranty