# How much power does a 120v 15A lighted switch use anyway?

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• posted on May 18, 2010, 2:02 pm

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Agree: We have a lighted switch still working some 40 years later with a small neon inside it. The neon glows when the switch is 'off'. Making it easy to find the switch in the dark! Presumably the switch mentioned by the OP is that? There are however other switches that light 'on' when the switch is operated, useful for indicating that something remote and out of site has been left on .................! In our case that could be "Oh. The lighted switch in the kitchen shows the garage light has been left on"! Typically indicators employ a neon using 'a couple of milliamps'. Probably around 115 x 0.003 = maybe 4 one hundredths of a watt at the most! 24 hours a day 365 days = 24 x 365 x 0.04 = 302 watts or 0.3 k.watt.hrs. each; per year. At ten cents per k.watt.hr that's about 3 cents per lighted switch, per year. That is the equivalent of leaving one 100 watt bulb switched on, once, for one or two seconds or so, longer than necessary!
A typical (neon) spec might be.
DC breakdown volts:70avg DC maintain volts:59avg after 100 hours at design current design current/milliamps 0.3 end of life is 5v change in breakdown for maintaining voltage maximum diameter:0.275inchs neon glow lamp pre-aged:no voltage range:105-125v
PS: Remembering that in operation there will be a small resistor in series with the neon indicator and the whole thing (resistor plus neon) will be across the 115 volt supply (switch off) so that most of the 302 watts per year will be dissipated by the resistor and least by the neon indicator itself. At this low power the resistor will not even get warm! Except academically the whole topic of how much power is used by each neon indicator, similar to those on appliances etc. is not worth bothering about. Leaving an outside door open for a few minutes during winter, for example, to bring in groceries on a cold/windy day, will entail more heating cost than a years use of ten such indicators!
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• posted on May 18, 2010, 5:20 pm
On Tue, 18 May 2010 07:02:52 -0700 (PDT), terry wrote:

Yes.
The only "problem" is that our energy here in sunny California is nowhere near 10¢ per KWh. I'm going to get my bill and come back with the actual numbers, but the first KWh is about 12¢ but that only lasts for a "baseline" which is about a week. Then the next week is double, then triple, then more than four times that when you get to the last week.
I'm figuring easily that it's 35¢/KWh here in California. Any other Californians out there that can help me on the math?
My math comes to about \$3.00/year for the dozen switches.
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• posted on June 6, 2010, 9:54 pm
On Tue, 18 May 2010 17:20:53 +0000 (UTC), Glenda Copeland

That's a big difference. It's about 8¢ here in east Texas (figuring from actual electric bills, NOT company ads).
[snip]
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Mark Lloyd
http://notstupid.us
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• posted on June 7, 2010, 5:04 am

Maybe OK in principle but ............ Problem is that based on \$2,50 per month (\$30.00 per year), if indeed it is that much? That just over 8 cents per-day is inconsequential in the overall cost of operating a North American home. (Less than 1% of energy bill). Eight cents per day is here (NE Canada) about 8/10ths of 1000 watt hours during one day, or the equivalent of leaving one 34 watt fluorescent tube light fixture on all the time!. Since we have a 9 'LED strip above our sink that uses ONE watt (total), which we leave on all the time, it's hard to perceive 'All the little indicator lights' adding up to anything significant!' Also recall that after WWII, in the UK, neon 'night lights' became available and my grandfather saying, with some delight, that he turned off everything in the house except the night light and 'The meter didn't even move'! As posted here previously, mains voltage neons use a milliamp or two, at 120 or 240 volts, LEDs probably less! And since all/most electrical energy entering a home ends up as heat within the house envelope anyway .................. !
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• posted on June 7, 2010, 4:59 pm
terry wrote:
<SNIP previously quoted stuff on power consumption of neon indicator lamps>

1% here, a fraction of a percent there and other places, half a percent in a couple more, another % in each of a couple other places... That often adds up to something significant.

LEDs usually take more. Few get less than 2 mA, and 10 mA is typical. Keep in mind that most indcator LEDs even now have chip chemistries that were available in the mid to late 1970's. That is done ecause they cost less than more efficient more modern ones. With an average supply voltage that LED power comes from likely being around 5 volts in consumer products other than power strips, along with losses in the power supply, I would expect typical power consumption by and associated with each LED glowing in the house to be ~.07 watt. What if there's a lot of those?
However, I would worry more about wallwarts being plugged in all the time and computers, monitors, TVs etc. drawing a few watts each when they are plugged in but "off", and 4-7W incandescent nightlights that can be replaced by 1/3-watt to 1-watt LED ones.

Which in most places costs more per BTU than natural gas, fuel oil and heat pumps do. And when it's not heating season, the electricity cost does not offset anything. And when it's air conditioning season, the cost is compounded.
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- Don Klipstein ( snipped-for-privacy@misty.com)

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• posted on June 7, 2010, 5:53 pm
On 06/06/10 10:04 PM, terry wrote:
<snip>

Indicator LEDs are about 2mA at 2VDV, so at 120VAC the losses in the transformer and rectifiers are far more than the power actually drawn by the LED. A neon lamp might actually be more efficient to run off of AC since you don't have all the losses of the magnetics. You could run an LED off low voltage AC and it would just illuminate on half of each cycle (some cyclists do this when they connect an LED directly to their dynamo without using a rectifier).
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• posted on May 18, 2010, 5:16 pm
On Tue, 18 May 2010 06:17:06 -0700 (PDT), keith wrote:

Using 0.1W, and averaging my electric rates (35¢/KW) for a dozen switches I get about 25¢/month or \$3.00/year.
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• posted on May 19, 2010, 5:36 am
On May 18, 3:16 pm, Glenda Copeland <gscopel...@Use-Author-Supplied- Address.invalid> wrote:

Ok on all those numbers but the spec I found showed each neon indicator using about 0.04 watts per hour.
Based on 0.3 milliamps at 115 volts. Thus wattage = current times voltage or (0.3 x 115)/1000 = 0.0345 watts per hour.
Per month that would be 24 x30 x 0.0345 = 24.84 watt/hours.
And at ten cents per 1000 watt hours (i.e. per kilowatt/hour) that'd cost 24.84/1000 x \$0.1 = approx 0.25 cents At 35 cents per kilowatt hour it would be 0.75 cents, per month. And for a dozen switches 0.75 x 12 = about 3 cents or of the order of 36 cents per year. Since we are all presuming, it seems, that the indicator light inside the switches will be off whenever whatever the switch controls is 'on' the indicators will cost even less than that. In other words if one is using electric lights, negligible!
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• posted on May 19, 2010, 12:56 pm

Just a nitpick, but .04 watts per hour is meaningless. It's .04 watt- hours per hour, or just .04 watts. One watt for one hour is defined to be one watt-hour.

No, it's .04 watts (if that's the number). You can't do some arithmetic, throwing away precision, and then come back to the same units with a different number. In this case you lost energy. At least you could have made a perpetual motion machine. ;-)

If one is using other appliances, such as refrigerators, water heaters, or clothes dryers, the lights themselves are (usually) negligible (if not, the whole bill is ;-).
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• posted on May 19, 2010, 10:43 pm
terry wrote:

Make that .04 watts, or .04 watt-hours per hour.

I have a lot of experience with a lighted switch at my "day job", and it is obvious to me that the neon lamp there is a "high intensity" type, probably C2A (NE-2H) or A1C ("mini NE2H").
http://www.cml-it.com/pdf/5-4.pdf says design current for NE-2H is 1.9 milliamps. Multiply by 120V, that means .228 watt. Since neon lamps don't conduct at less than 50-60V, I seem to think that average voltage used to push electrons through from 120 VAC is closer to 130V. That would mean closer to .25 watt.

35 cents per KWH does sound to me high. I thought Philadelphia was bad at around 14-15 cents per KWH. Chicago and NYC are close to Philadelphia in electricity cost as of last time I checked.
Meanwhile, I would balance lighted switches against another slice or two of pizza per year or a few more newspapers per year.
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- Don Klipstein ( snipped-for-privacy@misty.com)

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• posted on May 19, 2010, 10:18 pm
keith wrote:

Some sort of spec sheet for several neon lamps, including NE-2H, by CML Technologies (formerly Chicago Miniature Lamps):
http://www.cml-it.com/pdf/5-4.pdf
Design current of NE-2H is 1.9 milliamps. Multiply that by 120V and the result is .23 watt.
In Philadelphia and nearby suburbs in Pennsylvania, that currently amounts to 28-29 or so cents per year, likely to go up at least 10% in January 2011, assuming 24 hour per day operation. (USA national average would be more like 22 cents now.)
This does sound small. However, I would rather consider how much that adds up to over the life of the neon lamp, knock it down slightly due to paying-later while investments likely have rate-of-return exceeding inflation in electricity cost, and consider it to be part of the switch. Would you still buy the switch at that rate?
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- Don Klipstein ( snipped-for-privacy@misty.com)

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• posted on May 18, 2010, 5:37 pm
On Tue, 18 May 2010 01:53:25 +0000 (UTC), Glenda Copeland wrote:

You guys have cheap electricity!
I just pulled out my California PG&E bill to check the numbers (I can't believe you guys pay only a dime per Kwh!!!!!. Lucky you!)
My baseline is 365.4Kwh at 12¢/Kwh Then for 101% to 130% of baseline, it's 14¢/Kwh. For 131% to 200%, it's 29¢/Kwh. And, for the last few weeks of the month, at 201% to 300% of baseline, it's 43¢/month.
I averaged this to about 35¢/Kwh because I didn't know how to do the math otherwise (I used over 150 Kwh at the 131% to 200% rate and 256 Kwh at the 29¢ rate).
.1W/bulb x 12switches x 20hours/day x 365days/year x 35¢/Kwh x 1Kwh/1000KW = \$3.00/year
It would be nice to see what others pay for 201% to 300% over baseline 'cuz if it's 10¢, you have the deal of the century!
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• posted on May 18, 2010, 6:10 pm
Glenda Copeland wrote:

in our area, the rate during the day is 2x the rate for nighttime or weekends, so we try to schedule our heavy usage for off peak. nighttime rates are in the .07kwh range.
i run a couple of kilns, at about 8kh each, which can run for 2-3 days straight, so i couldn't afford to live in ca.
however, i just installed a 7.5kw pv cell array, so my day costs are 0.
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• posted on May 18, 2010, 6:54 pm
On May 18, 12:37 pm, Glenda Copeland <gscopel...@Use-Author-Supplied- Address.invalid> wrote:

\$.10, top to bottom, Winter and Summer (heat pump).
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• posted on May 18, 2010, 7:38 pm
Glenda Copeland wrote:

Nope, you have very expensive electricity.

You should be using the highest rate you actually get charged, because that is what you get charged for the extra electricity those switches use.

That conflicts with the previous para listing the rates unless that para is badly worded, particularly with the weeks bit.
If there is no week effect, just the charge that varys with the percentage of what you call the baseline, you should use the charge for the highest band you actually pay which will either be 28c or 43c

Thats hardly a shocking charge that will send you bankrupt any time soon even at the 43c rate.

We have the reverse type of charging, the rate drops the more you use.

Nope, its not that unusual when it comes from hydro.
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• posted on May 19, 2010, 1:50 am
Glenda Copeland wrote:

It's gonna get more expensive soon. Arizona provides about 30% of California's power, and Arizona is pissed.
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• posted on May 19, 2010, 12:58 pm

Actually, Arizona is well on the way to sending you their illegals.
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• posted on May 19, 2010, 5:06 pm
On 5/19/2010 5:58 AM keith spake thus:
>

Fine. We'll happily accept them here.
--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.
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• posted on May 19, 2010, 5:07 pm

That's good, because you're getting them in any case.
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• posted on May 19, 2010, 10:59 pm
Smitty Two wrote:

I seem to think that if such a "p!\$\$ing contest" develops along with ability to ship out illegal aliens, I would think that Arizona would send them back to California, Freight Collect. Maybe along with some of their own - especially if expelling illegal aliens from a state is legally easier of not forcing them to cross or dragging them across an international border.
If California gains competence and allowance at state level of government expelling illegal aliens, it appears to me that CA would do better to send them back outside USA as a whole. If not, I seem to think that CA is not in really good shape to tick off AZ.
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- Don Klipstein ( snipped-for-privacy@misty.com)