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I want to measure how much watts does my electric heater uses. It says it is a 2000W heater on a 110V outlet. I tried the kill-a-watt meter but that only goes max of 700W. What are some solutions to this?

JYelton
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Patoshi パトシ
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  • 2kW on 110V...I hope it comes with a 20A plug. You could get a clamp-on ammeter and an adapter to let you clamp around one wire. – vir Oct 19 '22 at 21:52
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    He probably means 120V. Nobody is on 110 anymore so far as I know. – Kyle B Oct 19 '22 at 22:03
  • I'd get an ammeter rated 20A and a "cheater cord". And I'd be very very careful.... Clamp on's are great but I wouldn't spend the $$$ for one single use. – Kyle B Oct 19 '22 at 22:04
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    The Kill-a-Watt should handle 2000W and give accurate readout, it just won't like it very much. When I did, it cried out in pain. Made me jump out of my skin, I had no earthly idea Kill-a-Watts *even had* speakers on them. – Harper - Reinstate Monica Oct 19 '22 at 22:23
  • @vir 20A plug is not enough. Heaters need a 125% derate, so it counts as a 2500W appliance. *That is more than 20A* unless you are relying on the artifice of AC power being counted as 125V, which many heaters do. But not all - they have 6000W @ 240V heaters which derate to 7500W (31.25A) necessitating a 40A circuit *for no darn reason*. – Harper - Reinstate Monica Oct 19 '22 at 22:44
  • There are NEMA 30 and 50 Amps plugs for 120 also. Travel Trailer plugs, for example (NEMA TT-30). – user57037 Oct 20 '22 at 00:52

2 Answers2

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"110V" is a marketing slogan from the 1910s. It's actually 120V in North America (rest of world can vary).

A 2000W heater on 120V is not legal if supplied with a standard North American/Japan/Taiwan plug (NEMA 1-15 or 5-15) because UL limits those to 1500W (12A @ 125V giving a 5V margin for variances).

If it has the unusual NEMA 5-20 plug, it may be allowed "2000W" (16A @ 125V). But then, you couldn't plug it into a Kill-a-Watt, which has a NEMA 5-15 socket.

If it is hardwired, look at the nameplate data on the heater.

If your actual voltage is less than the nameplate voltage, you need to figure out proportion (e.g. 110/125) and multiply that by the watts, twice. You need to do it twice because of how Watt's Law intercepts Ohm's Law. So for instance

 2000W * 110V / 125V * 110V / 125V = 1548 W.

I tried the kill-a-watt meter but that only goes max of 700W

Get a North American (or a real) Kill-A-Watt. They are certified for 1875W - This is a UL requirement because of the 15A type NEMA 5-15 socket they have on them, which has a worst-case power of 15A @ 125V.

However, in actual practice, Kill-a-Watts will work up to 20A for short times, and I've done it (malfunctioning old wall A/C)... however above 15A they will sound a warning buzzer. (made me jump out of my skin, let me tell you... I had no idea they could scream in pain!)

If yours has a 700W limit it may not be legitimate product. One must beware of AC mains equipment purchased mail-order. Most of it comes straight from you-know-where... and to say "it disrespects safety codes" is an understatement. The point of mail-order is to bypass the consumer protection apparatus which protects domestic supplies. Stick to reliable domestic supply bought over-the-counter at reputable shops. I'm referring to AC power things built into homes or plugged into homes. Obviously electronic components as one might buy at Mouser or Digi-Key are a different deal.

Harper - Reinstate Monica
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I found a number of panel meters on eBay for about $15-$20 that read power up to 22,000 watts (100 A 220 V). They also read voltage, current, power factor, kWh, and frequency. You would need to mount them in a suitable enclosure with power inlet and outlet.

There are other units that simply plug into your outlet and have an outlet where you can plug in your heater, but they only go up to 1800 watts.

These are also available from other retailers.

PStechPaul
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