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So I have a ventless dryer, and it's a relatively new LG model (LG DLEC855W 4.2 cu. ft. Compact Electric Dryer) that I have hooked up to a 120 V outlet.

I know it's not supposed to run on a 120 V outlet, and it honestly doesn't work great, but it does work, it does run, and it does eventually dry clothes.

However I have huge huge electric bills every month, US$600+ for a 900 sq foot (80 m2) home. I live in Florida and electric prices are average down here and even though it is summer it should not be this ridiculous. My only thought is that my girlfriend and my brother do laundry constantly and I'm not sure if this dryer, running on a lower voltage, drives up the price or not?

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    Hello, and welcome to Stack Exchange. This isn't an answer, but running a 240VAC device from a 120VAC might work passably, might waste enormous power, might trash the device, or might cause a fire. No way to tell. – Daniel Griscom Aug 24 '18 at 13:29
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    How exactly did you "hook it up" to that outlet? – chrylis Aug 24 '18 at 16:34
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    $600+ for a 900 sq. foot home??? I assume this cost started after installing the new dryer? Hire an electrician to give you a proper outlet for that thing. The electrician's work will pay for itself in 1-2 months of savings in electricity. – MonkeyZeus Aug 24 '18 at 16:55
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    If it's ventless, the heat is also having to be removed from your indoor air by your air conditioner. If running this dryer at the wrong voltage is requiring more energy for drying, that same extra energy is compounding the load on the air conditioner. – donjuedo Aug 24 '18 at 17:03
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    Not really an answer, but you're in Florida, land of Sunlight. Consider that line-drying clothes has zero electricity cost. I haven't used my dryer in 6 years. – Criggie Aug 25 '18 at 8:43
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Not an immediate danger, but quite a few problems

According to the spec sheet, this dryer is rated for 240V, 30A. Running it on "120V outlet" in the US normally means either 15A or 20A. Thanks to Ohm's law, if you run it on a 20A circuit you are probably safe. If you run it on a 15A circuit, there may be a safety issue. But in any case, there are plenty of other problems.

A dryer has three main power consuming sections - controls, drum motor and resistance heating elements. Typically (but can't tell for sure on any particular dryer without checking the schematics or the actual wiring), the controls & drum motor require 120V (Hot-Neutral) and the resistance heating requires 240V (Hot-Hot). If you manage to get the dryer working on 120V, then presumably you have everything working on Hot-Neutral.

As numerous others have pointed out, thanks to Ohm's law, if you cut the voltage in 1/2 and keep the resistance the same, the current will also be cut in 1/2 and the power produced by 1/4 (power = current x voltage). The result is nominally 4x the drying time. But due to other related factors, my gut feeling is that the drying time may actually increase by MORE than 4x. But we'll go with 4x.

Assume for the moment that the dryer uses, normally, 22A @ 240V for heating. That is now cut to 11A @ 120V and instead of 5,280 watts it is only 1,320 watts.

However, the drum motor (controls are minimal power on a modern machine), will still use the same power it used before. If it was previously 5A @ 120V, now it is still 5A @ 120V, so the total usage will now be 11A + 5A = 16A. If my numbers are correct (they are an arbitrary guess and may not represent reality, but they are one possible combination) then the usage of 16A would be greater than the normal capacity of a 15A 120V circuit. So there is a possibility of over-current if this is a 15A circuit and the numbers are "just right". It is also possible that this is a 20A circuit (no problem) or the numbers are a little different (e.g., heater 22A => 11A + electronics 1A + drum motor 2A = 14A total) and no problem. So there is a concern but it is NOT my original "BIG PROBLEM".

As far as electricity cost: In theory, if 120V == 1/4 the heat produced and the clothes dry in exactly 4x the normal time, then your electricity costs would be the same as running at 240V. However, it is quite likely that the clothes take substantially MORE than four times as long to dry for "physics reasons" (I can't get into it all right now, though I still stand by that statement despite my retraction of the imminent safety issue).

Bottom line: Your current setup:

  • May be a real hazard due to possible over-current of wiring and equipment
  • Is a waste of energy (as you already suspected)
  • Takes way too long to dry your clothes (as you already know)
  • Is almost certainly shortening the life of the dryer due to use beyond the design

Get it fixed - put in a proper 4-wire NEMA 14-30 outlet, a 30A 2-pole breaker and appropriate wiring (minimum 10 gauge copper).

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    The heating coil is a resistor so if the voltage is halved, then the current will be halved (I = V / R). But this doesn't take into consideration that the resistance of the heating coil decreases with temperature so the current will be somewhat more than half (by how much more I couldn't say). The power consumed P = I V should therefore be about 1/4. – Jim Stewart Aug 24 '18 at 14:33
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    The OP hasn't said how he wired this up. Maybe the heating element is not being powered at all and the clothes are being air dried. I was assuming that somehow he wired one side of the coil to the 120 V and the other to the neutral. – Jim Stewart Aug 24 '18 at 14:38
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    Motors, especially, do not react well to the wrong voltage. It is the motor turning at speed that produces the back EMF required to limit the current. With half the rated voltage the current might, in fact, be much higher with the motor unable to turn fast enough at the lower voltage. The condenser for a ventless dryer will also be running a compressor motor and is also probably not working correctly, or anywhere near its nominal operating efficiency. – J... Aug 24 '18 at 19:48
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    And another point for your bottom line, as @donjuedo pointed out above: since it's ventless, any heat it does produce is being dumped into the house, which means the AC system has to remove it. Which is also putting undue stress on the AC system, certainly costing more to run it, and potentially reducing its lifespan. – GalacticCowboy Aug 24 '18 at 19:50
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    WRONG conclusion still in answer title and below in recap even though you discussed the basic math. The dryer will draw less current on a 120v circuit and take much longer to dry. – Ed Beal Aug 24 '18 at 21:24
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You are running the dryer without full power, which will drastically increase the time it takes to dry clothes. If you're doing it on a timed basis, your clothes won't get dry. If you use it on a moisture sensor setting, it'll take way longer than otherwise.

Additionally, you're using the dryer in a manner for which it was not intended. If it has any effect on the dryer at all, it will be to shorten the lifespan of the dryer.

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    This is the most likely explanation, if the dryer power usage is the actual culprit. Cutting heat and fan speed to 1/4th could easily increase drying time a lot, all the while heat losses and friction losses remain the same. – jpa Aug 24 '18 at 19:27
  • I agree it will take much longer to dry running the drum longer will end up cost more as the heat created is less than 1/2.+ – Ed Beal Aug 24 '18 at 21:15
  • Good point on the wear and tear by unnecessary usage. – Kris Aug 24 '18 at 21:46
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I would say it's probably causing you some issues. Most dryers are designed to pull 30A off of both phases combined (your model requires 30A). While the drum might run on 20A, my bet is the heating elements aren't doing all they could. So that means they're probably running the dryer for a LOT longer until the clothes are dry. Which means you're getting a lot of drum tumbling and not a lot of dry.

Try to get a 30A line in there and I bet the costs drop.

  • Do electric dryers usually pull 20A for the drum? I would have thought more power for the heater less for the drum but I don't really know. – The Evil Greebo Aug 24 '18 at 14:37
  • It depends a lot on how the dryer breaks down the power usage. Older dryers use a single 115 to power electronics and the drum, while the other powers the heating elements. These newer dryers might use less than the full 115 to power the drum so it's not unreasonable to assume it might just try to use the remainder towards heating. Either way 20A is not enough. – Machavity Aug 24 '18 at 15:04
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    I have a gas dryer and it's got a 15A plug on it. I can't think of a reason that an electric dryer would need more power for the drum and electronics than a gas dryer would. – JimmyJames Aug 24 '18 at 18:05
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    The drum motor is a fractional horsepower motor in every dryer I have worked on and usually runs on 120v. The heating element is usually the only 240 part because 240 is more efficient when looking at power in watts. – Ed Beal Aug 24 '18 at 21:28
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All good answers, but one thing that is likely happening here is that the opinions are based on the OLD model of how a clothes dryer functions. A "condensing" dryer is different. It is, for all intents and purposes, using a "heat pump" type of system to remove the MOISTURE from the clothes, but at low(er) temperatures that the old heater type. There is an air circulating fan that pushes the warm dried air from the "hot" side of the heat pump into the clothes chamber, then the moist return air passes over the "cold" side of the heat pump where the moisture condenses on the coils and is drained away. So that heat pump has a small refrigerant compressor as the heat source and moisture condenser.

In some models, and I suspect this is one of them, they use TWO heat pump compressors in parallel, each one powered by 120V, and the microprocessor decides how much each or both of them run. That would totally explain why it is able to function with only 120V, it is just never able to kick in that second condenser, which also explains why it takes so long to dry. So it's as if you have it set for "Delicates" even if you have selected "Bedding" for the program; it can't do any more than that, so when you put in some sort of heavier load, it is going to run for a LOT longer, and I agree, likely 4x longer than it should.

That aspect is still the same as was previously explained; the longer it has to run, the more energy it uses per load because the tumbler motor and circulating fans are still running at full load fro 4x the time, even though the moisture removal portion is at 1/2 load.

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As everyone else has pointed out, you ought to fix your incorrect install for a good variety of reasons. However, it's probably not the cause of your $600 bill. Some simple math:

If you pulling 16A @ 120V for 12 hours a day, every day, for the entire month, that's ≈700 kWh. (You just multiply all that together 16 × 120 × 12 × 30.5 ≈ 700,000 Wh, divide by 1,000 gets 700 kWh.) You can then compare that to your electric rates or just compare to the number of kWh used in the month, which should be on the bill.

I'd suggest starting with asking your neighbors about their power bills, especially if their houses are similar, to see how abnormal your bill is. Then you can look at your electric meter to see how much power you're using at a given moment, as you turn things on and off to see which matter.

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