Maxcio PM-01 - power meter (and more!)

Measuring (and killing) unwanted watts!

[Maxcio PM01]
[Italian version here]

Product name: Maxcio PM-01 - wattmeter
Manufacturer: Ningbo Cowell Electronics Tech. LTD - China
Cost: ±25€
Reviewer: Lucio Cadeddu - TNT-Audio Italy
Reviewed: May, 2023


Monitoring energy consumption is never an easy task, and for various reasons: manufacturers' claimed data are not always precise, and normally refer to max power absorption (which isn't always the case) and stand-by power consumption is rarely declared, or is incorrect.

One might need a device that constantly measures power consumption, dynamically, and that can monitor any device over, say, 24 hours. Such a device might help us understand how many watts our amplifer is delivering to our speakers, by means of a simple calculation. Here's how: take into account that a Class D amp wastes only 10-20% of power into heat, while a Class AB amp wastes 50% of power and a Class A amp wastes 75% of power. The rest goes to the speakers. Hence, if your amp is using 100 watts, it is easy to guess, knowning its class, how many watts are delivered to your speakers and, hence, how many REAL watts you need. Be prepared for huge surprises!

[Maxcio PM01]

Moreover, it would be interesting to know how many watts your HiFi systems uses while in stand-by mode or even while it seems completely off. Well, such devices exist, and this Maxcio PM-01 does exactly all of the above, and much more! It also measures the status of your mains (voltage and frequency), how many amperes your components are drawing from the mains, and how many kWh of your electrical bill are due to your HiFi.

This innocent device will not be welcomed by amplifier manufacturers and HiFi dealers, trust me.

Tech specs

In use

Being designed for people who ignore the first thing about power and electricity, it is extremely user-friendly: just plug it into a wall socket, then connect the appliance you wish to monitor...and you're done. Just allow some time for the energy consumption to settle down. My smart TV, for example, absorbs some power during the first 15 seconds, then enters into intellingent stand-by mode, consuming 0 watts.

By means of the Function switch you can decide to measure watts, amperes, kWh or €/UKP/$. Of course, you need to use the switch Cost to enter the cost of a kWh, according to your energy supplier plan. The device offers the possibility to keep in memory previous measurements, and peaks (min/max). Data won't be lost once unplugged, because it uses an internal back-up Ni-Mh battery. The display backlighting is a useful feature when the mains socket is out of reach.

I've tested this device on any electrical/electronic component at home, and there have been various “surprises”. A preamplifier, for example, though appearing completely off (no stand-by led, no display) absorbs up to 8 watts, doing nothing.
My CD transport absorbs 2 watts while in stand-by mode, just to power a dreadful blue led. A Class D power amp, when switched on (without playing music!) absorbs nearly 20 watts. A soundbar absorbs 0.8 watts while in stand-by and 5 watts when playing (a little bit more at full volume).

In other words, if your HiFi system is complex, with many components permanently switched on or in stand-by mode, it might absorb from the mains enough power to keep all the lights of your house on 24 hours a day (!!!).

[Maxcio PM01 Schuko]

Now, if you wish to know how many real watts your speakers are needing, measure the power absorption of your amp while it is playing, then subtract the part of energy it wastes (as said before, this depends on its class, A, AB or D). Now take a good SPL meter and measure the sound pressure at the listening seat. This, together with the sensitivity datum of your loudspeakers, should give you another gross estimate of the amount of watts you really need. Trust me, it will be much lower than you'd ever imagine!

While you're there, connect this device to any other electronic component at home. You'll discover that:

Of course, your devices might be different, so test them!

N. B.: the PM-01 can manage loads up to 3680 watts or 16A (EU version) or 13A/3120 watts if it's the UK version. An overload warning will light up if you connect something that exceeds these limits.


It is easy to find it at the usual online stores (Amazon, Ebay etc.) for 20€/$/UKP, or for much less on Aliexpress, even under different brands. There are more sophisticated power meters out there, if you fancy, such as those that can be interfaced via Bluetooth with your smartphone, like this one!


This Maxcio PM01 is an extremely interesting and useful tool, that might help you both debunking some myths on real power output of amplifiers and saving costs on your electrical bill at the same time. Its cost will be rapidly written off in a couple of months thanks to the energy saving on your bills.

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