You can, but one of those wall plug-in power meters are recommended for your use case.
I have one that looks like this, there are many clones that will do just fine, which gives W, A or V and you can even put a price per kWh to have it give you the cost of running.
Just a heads up OP worth checking your state, country or councils government websites that note about electricity. Some of them give free power/watt checkers to help people reduce their electricity usage.
For all the reasons others have already stated, what you want is a Kill A Watt instead of a multimeter or another thing to buy. Plug this thing into the wall and then plug your appliances etc into the meter and leave it for a week. I will record total power draw over the duration so you can see exactly how much power is being used under normal operating conditions. With a little bit of math you can compare kilowatt hours consumed with your power company costs and figure out how much money it cost to use TV's etc per hour.
If you’re the kind of person who doesn’t know how to do this, you probably don’t have a true RMS meter and getting any kind of accurate reading is probably a no go.
Also something like a TV has a highly variable power draw, so a measurement of power over a longer time is probably more useful than a momentary snapshot. This is why most energy rating have something like kwh per year for some kind of defined typical usage.
Yes, but differentiating between actual power and apparent power will be difficult without building a rather complex circuit. A dedicated power meter will tell you, as well as computing the power factor. On the flip side, a TV’s switching power suppy should have a good power factor, so apparent power (AC amps * RMS volts) is close to actual power.
You can, but you would be better off buying something like this:
Upgraded Watt Power Meter Plug Home Electrical Usage Monitor Consumption, Energy Voltage Amps Kill Tester with Backlight, Overload Protection, 7 Modes Display a.co/d/bj4U2hA
Hilariously enough, I now use my portable power station(like these www.techradar.com/best/portable-power-stations) to do this kind of testing. It has a watts output on the front panel, so I can just plug something in and see how much it draws.
This is tricky, as power is calculated as voltage x current. Measuring (or knowing) voltage is usually pretty straightforward. But accurately measuring current requires setting up the circuit so it flows through the multimeter (while set to whatever current measurement mode it has - usually “Amps A/C”, or similar). However, this method isn’t safe, or practical, for non-electricians to measure A/C appliances.
As someone else mentioned, you could buy a multimeter that has an “amp clamp” - effectively a non-contact way of measuring current. BUT, you need to be aware…
A typical appliance’s cable will have both active and neutral wires inside the outer layer of insulation. Current flows through a circuit - up one wire and down the other, if you will. So an amp clamp can only measure the current on one of those wires. If you were to measure both at once (ie. clamp the whole cable), the readings in each direction will cancel each other out. You’ll measure zero net current. The only way is to cut the outer insulation and clamp a single wire inside.
I would absolutely NOT recommend this for an A/C appliance. The possibility of accidentally cutting through the insulation of one of the inner wires, combined with the possible death of the person handling it afterwards, should make this a non-starter.
Your safest options for ANY A/C powered appliance are to either:
rely on the manufacturer’s label; or
buy a smart plug that measures the current for you.
There’s many, many brands for the latter available, and most are really quite affordable.
Edit: as another commenter said, you could possibly buy a short extension lead that splits the wires out for you, but now you’re buying a non-standard extension lead and (possibly) a new multimeter, all to validate what’s on the appliance’s label.
A $20 smart plug with current measurement will still be your cheapest and safest option.
The theory beside measuring power with a multimeter you way even have done it in high school usinq a 12V power supply and a small resistor/motor. Fun exercise and you may even loop on the whole high school physics curriculum with electricity --> power --> force --> work --> Energy and efficiency calculation.
However, unlike the 12 V you work on at school the domestic 230V can kill you (same for US 110V). I don’t see a safe way to use a regular multimeter to measure a current in these voltage range. If you know what you do, you’ll build a dedicaced/enclosed set up. If you don’t buy a watt meter at the hardwarc store, it’ll be safer and cheaper than a DIY one
Even this probably won’t result work though because you need to put the clamp around only one wire, not the entire power cable that has live, neutral, ground.
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