G.T. Power Watt Meter

Creation date: June 23rd, 2010

Thanks to Dale over at EPBuddy for sending me a G.T. Power Watt Meter to use, review and show off.

Ever wanted to know if you sized a battery, motor or speed control properly? Or how much current your charger is drawing? Well there are many solutions that will tell you, in one way or another, these things but not many are in a nice clean little package, and very few are tailored toward rc hobby use. The G.T. Power Watt Meter offers hobbyists exactly what they need in a small device that shows amperage, wattage, voltage, amp-hour and watt-hour, and all for about $30.

First impressions
The G.T. Power Watt Meter comes in a small box. Inside is the watt meter and instruction booklet. The meter ships without connectors on its 12awg wire inputs and outputs. The meter is not tiny but neither is it large. One might say it is just about the right size. The wires extend about 3in from the case and are pre-tinned. The case is made from a rubbery plastic and has no buttons, switches or the like. The only thing, other than the LCD screen, is a small axillary battery port on the side and some cooling vents on the back.

Using the Watt Meter
I soldered 4mm bullets (same size as banana plugs) to my meter, males on the source side and females on the load side. This makes it fairly simple to interface to and will allow it to be plugged directly inline on either my power supply or charger.

I plugged the watt meter into my power supply and switched it on. The meter came to life and promptly displayed the voltage of my power supply, with all other fields reading "0.0". I then watched the screen cycle through all the various "Data Queue" items.

Testing the accuracy of the meter
Next hooked watt meter up to my 12V power supply then to my reconfigurable light bulb load. Then I placed a multimeter inline with that and powered it all on. My custom light bulb load offers both approximate 5A and 10A loads.

Difference of about 2% at ~5A

Difference of about 3% at ~10A

What does this 2-3% deviation mean? Honestly I don't know as I don't know which, if either, is more accurate. I do know that measuring current flow accurately is not easy, so there will likely always be slight error involved. As such I will call the 2-3% deviation well within the acceptable range.

My first use of the meter
I used this meter for my review of the iCharger 206B in order to look at the input requirements, output capabilities and charger efficiency, and it worked great. Here are some photos of the watt meter in action.

In conclusion
The G.T. Power Watt Meter is a simple device that can easily give you information that is otherwise difficult to obtain. It is trivial to use, offers an easy to read screen and shows very useful information, all for a very good price.

Specs - Features - Photos


Input voltage
(L * W * D)
85 * 42 * 25 mm
(3.35 * 1.65 * 0.98in)
150g (5.3oz)
Range: resolution
0-130A: 0.01A
Voltage0-60V: 0.01V
Wattage0-6554W: 0.1W
Amp-hour (Ah)
0-65Ah: 0.001Ah
Watt-hour (Wh)
0-6554Wh: 0.1Wh

  • Backlit LCD screen
  • Data Queue cycles through Ah, Wh, Ap (amp peak), Vm (voltage min) and Wp (watt peak)
Stock photo

User manual snapshots