EV charging

EV charging slower than expected

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)

You have a “7kW” home charger, but your car’s dashboard says it’s only receiving 1.4kW or 3.5kW. The estimated “time to full” is 20 hours instead of 6.

What’s normal vs not normal

Normal:

  • Slower charging when the battery is nearly full (above 80%).
  • Slower charging in very cold weather (the battery needs to warm up).
  • The charger slowing down if you are using the oven, shower, and washing machine at the same time (Load Balancing).

Not normal:

  • Only getting “Granny Cable” speeds (2.3kW) from a dedicated wallbox in perfect conditions.
  • The charging speed dropping to zero frequently.

Likely causes (ranked)

  1. Car Settings: A “Maximum Charge Current” or “Reduced AC Charging” limit set in the car’s infotainment menu.
  2. Load Balancing: Your home’s total power usage is high, so the charger is automatically throttling back to protect the fuse.
  3. Solar Matching: Your charger is set to “Eco” or “Solar Only” mode and there isn’t enough sun.
  4. Scheduled Charging: The car or charger is waiting for a “Cheap Window” and is only providing a “trickle” until then.
  5. Faulty Cable: Using a “16-Amp” cable (3.6kW) with a “32-Amp” charger (7.2kW).

Quick checks you can do safely

  • Check your car’s screen for any “Charge Limit” or “Amperage” settings.
  • Check your charger’s app to see if it’s in a “Solar” or “Eco” mode.
  • Ensure the charging cable is pushed firmly into both the car and the charger.

When to call an installer

  • If the charger never reaches 7kW even when the house is empty and the battery is at 20%.
  • If the charger or the cable feels excessively hot during use.
  • If you suspect the “CT clamp” (load sensor) has been installed incorrectly.

Questions to ask your installer

  • “Is the ‘Master Current’ limit on the charger set to 32A?”
  • “Is the load balancing configured to my house’s actual fuse rating (e.g., 60A or 100A)?”
  • “Is the firmware on the charger up to date?”

Related NetZeroNow tools & guides

FAQs

What is ‘7kW’? Most UK homes have single-phase electricity, which allows for a maximum charging speed of about 7.2 kilowatts (kW) or 32 Amps.

Why does it slow down at the end? Think of it like filling a stadium with people. At first, they can run in through all doors. As it gets full, they have to find individual empty seats, which takes longer. This protects the battery.

Does the cable matter? Yes. If you bought your own cable, ensure it is rated for “32 Amps” or “22kW”. A cheaper “16 Amp” cable will limit you to 3.6kW regardless of your charger.

Can I get 22kW at home? Only if you have “Three-Phase” electricity, which is very rare in standard UK homes. Most people are limited to 7kW.

Why is it slow in winter? The car may use some of the incoming electricity to heat the battery pack before it starts “storing” it, which reduces the effective charging speed.

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