It shows which profile was actually negotiated

The best USB power meters for 2026

A USB meter plugs between a charger and a device and shows the voltage and current actually flowing, which is the only way to know whether a fast-charge claim is being honoured. The measurement specifications are the ranges and the resolution: a meter reading to a hundredth of a volt and a milliamp resolves a trickle charge, one reading to a tenth does not. What separates this shelf from a plain ammeter is protocol awareness: a good meter identifies the profile in use — Power Delivery at a stated voltage, PPS, Quick Charge — and the better ones include a trigger function that requests a given profile so a charger can be tested without a device. Data pass-through matters if the cable also carries data, and not every meter supports it at full speed. Display and logging close the list: a colour screen with a graph, a stored energy total in watt-hours, and on some models an app over Bluetooth. The meter’s own consumption is small but real, and it is part of any measurement made through it. We compare voltage and current range, resolution, protocol identification, trigger function, data pass-through, display and logging.

Every part on this shelf, side by side

1. 

   Retoo USB tester, 4–20 V, 0–3 A, capacity to 99999 mAh

   A USB 2.0 power meter measuring 4 to 20 V and 0 to 3 A with a capacity counter to 99999 mAh, showing voltage, current, time and capacity on an LCD.

   Voltage and current range

   DC 4 V to 20 V and 0 A to 3 A, first bullet

   Resolution

   Nowhere in the listing

   Protocol identification

   Nowhere in the listing — it measures voltage and current without identifying a charging protocol

   Trigger function

   Nowhere in the listing

   Data pass-through

   USB 2.0, plugged between the port and the device with no driver or software, third bullet

   Display

   An LCD showing four values at once: voltage, current, elapsed measuring time and capacity, second bullet

   Logging

   A memory function for running or completed measurements, with a reset, fourth bullet

   Amazon reference

   B09QXLS5JP (same reference on 5 Amazon marketplaces)

   EAN

   5904094227396

   • Four values on screen at once, including elapsed time and accumulated capacity
   • No driver and no software — it works with anything that has a USB port
   • No resolution published, so the smallest readable current is unknown

   Best for: Checking what a power bank actually holds and what a charger actually delivers.

   ≈ €5

   Check price on Amazon
2. 

   Treedix USB CABLE tester: pins, resistance, E-marker, 2.4 in colour screen

   A battery-powered USB cable tester that checks internal pin connections, resistance values, basic USB functions and E-marker chips on a 2.4 inch colour display.

   Voltage and current range

   NOWHERE IN THE LISTING — this instrument tests cables and does not measure charging voltage or current

   Resolution

   Resistance values are read, first bullet; no resolution is published

   Protocol identification

   Reads USB-C E-marker chips and detects USB 2.0, 3.2 and 4.0, first and second bullets — the only instrument in this family to identify anything

   Trigger function

   Nowhere in the listing

   Data pass-through

   None — both ends of the cable plug into the tester itself rather than between a charger and a device, fourth bullet

   Display

   A 2.4 inch high-resolution colour display, fifth bullet

   Logging

   Nowhere in the listing; battery-powered for portable testing

   Amazon reference

   B0DYJG773N (same reference on 4 Amazon marketplaces)

   EAN

   0644197775077

   • It reads E-marker chips, which is what separates two identical-looking USB-C cables
   • Pin-by-pin connection testing, so a cable can be diagnosed rather than binned
   • It does not measure charging voltage or current at all, despite sitting on this shelf

   Best for: Sorting a drawer of visually identical USB-C cables into what each one can actually do.

   ≈ €47

   Check price on Amazon