Why is my electric car charging more slowly than expected?

There isn’t one rate that fits every car and session. Start by comparing like with like: same vehicle, similar starting charge, similar conditions, and similar charger details. For Tesla Supercharging, Tesla lists state of charge, ambient temperature, battery-pack size and age, and vehicle configuration among factors affecting rate. It also says charging slows as the battery fills, with reaching 100% typically taking significantly longer than reaching 80%. [S1]

That source is Tesla-specific; it does not set an expected rate for other makes, chargers, or individual sessions. Your owner’s manual and the vehicle’s own charging display are better references for your model.

Record a few snapshots rather than relying on memory. Note the start and end times, starting and ending state of charge, and any power or charging rate the car displays. Add the charger’s identifying details and its advertised capability if available, plus the weather or temperature information you can observe. Keep these as observations, not proof of a fault.

For a Model S, the manual says the touchscreen displays charging power and rate, and says the vehicle may heat or cool the battery when needed during charging; charging can be delayed while that happens. [S2] Those details are specific to that manual, so check your own vehicle’s manual or display for equivalent information.

A worksheet can help narrow what to ask, but it cannot identify the cause by itself. Compare your recorded rate with the charger capability shown to you and the limits or guidance stated for your particular vehicle. Don’t assume the charger’s advertised figure is what your car should receive in every session; the supplied sources do not establish a universal expected rate or explain how every make balances charger and vehicle limits.

If the car’s display gives a reason, copy its wording exactly. If you don’t see an explanation, record that too. Ask the charging provider whether the session or charger showed an issue, and ask the vehicle maker what rate range or conditions apply to your specific model. Share the vehicle year and model only through the support channel you choose.

Use one row per session, and avoid treating different starting charge levels as a fair one-to-one test. For example, these are placeholders, not measured results:

Session A: [date/time] | [car/model] | start [25%] | end [ ] | duration [ ] | charger [type/ID] | advertised capability [ ] | displayed power/rate at start, middle, end [ ] | conditions [ ] | message shown [ ]

Session B: [date/time] | [same car/model?] | start [higher %] | end [ ] | duration [ ] | charger [type/ID] | advertised capability [ ] | displayed power/rate at start, middle, end [ ] | conditions [ ] | message shown [ ]

If the rate falls as the battery fills, that pattern may be consistent with Tesla’s description of Supercharging, but it does not prove that every vehicle or session is behaving normally. [S1] Compare the entries and take the worksheet to the relevant provider or vehicle support team.

First check that you are comparing the same thing: the car’s displayed power or rate, at a similar starting charge, rather than total time alone. Capture any messages and note whether the displayed rate changes during the session. If your vehicle manual describes battery conditioning or another charging delay, use its wording as your guide; the Model S manual’s battery heating or cooling note should not be generalized to other models. [S2]

If repeated notes show a similar concern under comparable conditions, send the dated worksheet to the vehicle maker or charging provider and ask what model-specific limits and session information they need. Don’t attempt repairs based on this comparison.