How many computers on one 15 amp household circuit?

In my living room I currently have 5 Computers, 5 x 20 inch LCD's, 2 Laptops and a large house fan to keep me cool.

I am about to change my setup and buy a nice 6 monitor stand and add a $5000 top end gaming pc with all the best gear and a 1000 watt power supply.

Checking my breaker box I see that the rating on this circuit says 15 amps. Do you think I'm close to blowing the circuit? What is the most any of you have put on one 15 amp wall circuit?

Would love to hear some suggestions to how far we can go on one 15 amp household circuit.

what you do is you take your total watts.. les say 500 and divided it by your voltage.. we'll say 120.

so you have 5 computers that all run at 500 watts. that comes to 2500 watts. then you take that and divide that by your voltage we'll say 120 but some are 230 (i believe) which comes out to 20 amps.


Keep in mind I just took the Wattage of your power supply. you need to take the wattage of your..

laptops, monitors house fan, lights, tv if you have one on and other stuff.

I am sure you will need to pull from 3 different breakers at the least. :wink:

Thanks man, I must be right on the edge already then.

Do you know if its a limitation of the wires in the wall or can I change out a 15amp circuit for a 20amp in my breaker box (i would have an electrician do it of course if its possible).

yiiha.. electrical stuff with my broken english :)

let's give it a try


I've got a 16 amp circuit.
and 230V on the cables

so 16 * 230 = 3680 Watts

I've installed several "power counters" on each socket (I think it's called so? the thingy where u plug the power cable into *g*) which are connected to the circuit I want to use. So I can see the current amount of watts which are in use and the watt crits (if a gfx-card needs more power for a short moment etc). I'm currently on 3180 watts for my entire system so I got a lil space left.

those "power counters" cost on german ebay about 10 euro each and they can show you how much your entire system costs... per minute... per hour... per day.... outch :)

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Do you know if its a limitation of the wires in the wall or can I change out a 15amp circuit for a 20amp in my breaker box (i would have an electrician do it of course if its possible).

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depends on the line. every cable can handle a fixed amount of power. if the cable is thick enough so it can handle the 20amp then you can change it. an electrican can tell you that because he can measure the cable . be careful with that - if the cable can't handle the 20amp it will burn =)

I have 7 computers, 32' tv (with cable box, dvd player and all that jazz) 7 monitors, 2 of which are CRTS.

PCS 500w x 7
CRT 145w x 2
LCD 90w? x 5

TV and all that junk no idea

Fan, phone, answer machine.

Hell I have 5 computers and monitors plugged in to ONE outlet.

All this stuff is all on one circuit.

No idea what the limit is. I couldn't plug in a space heater without the breaker going off, but I can run all this stuff. So far so good!

Electric bill is a bit scary :shock:

If you plan on changing the main Breaker (fuse?) for the whole circuit. Does that curcuit just supply your room or is it like a bedroom/office/downstairs/etc ring? Either way get an electrician in, it'll cost you more short term but then re-building the house having burnt it down with an electrical fire in the walls will cost more. Generally speaking what ever the circuit is rated for 20A 15A whatever, will be lower than what the circuit can handle but the more it handles to higher the chance of catastrophic failure...

Disclaimer: I am not a licensed electrician. But I can install new circuits and I have a healthy respect for currents. Plus, the math is pretty easy to do.

15 Amps = 120*15 Watts Non Peak.

Or 1800 Watts

Of which, 80% can be in use for lengthy periods of time.

So 1440 Watts can safely be used on a 15 amp circuit for extended periods of time. 1920 Watts in a 20 amp. To power all of my machines, I ran 3 extra 20 amp lines (plus the existing 15 amp line). HOWEVER - this is overkill. I would have been ok with 1 extra 20 amp line and I suspect most of you here will also be unless you wind up with something crazy.

Keep in mind that a 1000 watt power supply WILL NOT continually pull 1000 watts. I have one, powering a quad core with 3x 8800GTXes. IDLE they pull 400 watts from the wall. Power supplies actually waste about 20% of their total power being used (none can reach 100% efficiency).

I have spoken a bit about this in my FAQ - take a look there. There are also cheap devices like the Kill-A-Watt that can read power consumption at the wall. Buy one and measure. If you do go the extension cord route (I don't suggest this but it is possible) then make SURE you get one PROPERLY rated or else it could over heat and cause a fire. Meaning, DO NOT use a 100' 20 gauge cord on a 20 amp rated breaker.

If in doubt - consult a qualified electrician, please.

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Originally Posted by Nitro

Thanks man, I must be right on the edge already then.

Do you know if its a limitation of the wires in the wall or can I change out a 15amp circuit for a 20amp in my breaker box (i would have an electrician do it of course if its possible).

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Most likely no, you cannot. This would be dangerous. Almost NO builders over build if they don't need to. Less money in their pockets and they are already meeting code.

So the lines are VERY UNLIKELY to be able to safely carry that higher current. It would work of course (as would bypassing the breaker all together but would be VERY unsafe. Do NOT do that. Take the time to pay a licensed electrician to run the extra line and do it properly.

I had 7 computers (plus TV, Amp, cable box, NO lights) on one circuit, and it'd trip out once a month. Usually happen when I was zoning and all the hard drives kicked in.

I went to add an 8th computer (high end, 750 watt etc) and had to move 3 of the low end computers to a different circuit. I used a thick extension cord and ran it from the other room. It would get warm, but never hot.

If you're serious about this, I would suggest removing any unnecessary hardware from the bot computers (mainly the CD-ROM drives). If you are spec'ing out new computers, keep power usage in mind. Not only can you run more computers on a single circuit... it will cost less in the long run as well!

If you are careful to avoid high power draining devices (heaters, motors, refrigerators, AC units, etc) and are sure that nothing else but your computers are on said 15 amp circuit (generally an entire room or sometimes even two rooms may be on the same circuit) then it is POSSIBLE to run 5 computers and 5 LCD monitors on a single circuit. But very little else. Figure each computer will be around 250 watts... that is 1250 - within the limits for continual use. This is assuming a "normal" computer setup and a low power LCD monitor. Use a CRT and also put a refrigerator or other high amp devices on the same circuit and you will most likely trip. Any lights, particularly high energy incandescents will use . 40 - 60 watts EACH. This can add up quickly and put you over the edge.

Add everything up that is plugged in. Every device will have its power consumption listed on it, either in Amps (multiply that by 120 to get watts) or in watts. It would be helpful to read the actual power use from the wall though and add all of those up.

Note that you can push this further as some of you are likely doing. You can run 2000 watts on a 15 amp breaker. You can also swim with sharks. It SHOULD eventually trip (to save your house/life). However, if this is very stupid to do. If the breaker fails to trip, you could start a fire. I DO NOT suggest that you push the envelope when it comes to electrical use. There are codes and limits for a reason. You can jury rig things with a PROPERLY RATED extension cord but if in doubt, consult a professional.

Thanks for all the info guys, I will take power consumption into consideration when purchasing any further parts, with this in mind I think I will get an array of 6 of these monitors http://www.newegg.com/Product/Produc...82E16824001226

Only 36 watts each

You might want to pick up one of these to get an idea of how much power you're really using.

http://www.amazon.com/P3-Internation.../dp/B00009MDBU

I'm somewhat lucky in that I have a dedicated 20 amp circuit for my computers (formerly for an air conditioner.)

i;m going to get me one of those kill a watt things. I really would like to know the juice all my PC stuff pulls. It would be interesting to know how much it costs me an hour to use all of it.

Lucky for me, my house has a 115v 30 amp circuit in the basement. It used to be for the dryer and sump pump, but the dryer at some point was replaced with gas. The sump pump draws around 8A if I remember... 1 HP motor?
Anyways I hooked up a 2000VA UPS to suck up the spike from the sump pump kicking in (runs a couple times per day, more if there's raid), it's more than enough to run multiple computers, TV, game consoles, beer fridge, etc without any problems.

Speaking of power use - my bill came today. I figured it would be a bit much because of the new AC system and well 10 computers plus 2 servers plus my monitor array.....

It was over $500.

Ouch :)

I calculated my monitor array alone costs over $50 a month to run. 10 computers runs about $200 per month. Maybe I should hibernate / standby when not in use.......

Yeah....

Heh...seeing this thread reminded me that I need to do this myself. Mine are on 24/7 except for the monitors. Need to verify just what these things are doing as I think it costs me probably $100 extra here, too. :P

I will not be doing the sleep/hibernate thing, though. Power management is way too buggy for daily use for a gaming rig, IMO. And it usually manifests itself as weird intermittent bugs that are a PITA to lock down. Better these days than it used to be but still not something I want going on if I can possibly avoid it.

I have wake on lan going and I actually powered down the other 8 computers when I was not playing on them. So uhh yeah..... not really sure how else to minimize power use here.

I have them setup to boot and automatically run WoW - takes only a few seconds.. I have to switch my monitors from A to B anyway (manual hardware switch) and log in anyway - so it is not a big deal.

Cooling is a big one - that thing runs nearly constantly. 2 Ton AC unit.... 30 Amp breaker.... adds up.

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Originally Posted by Fursphere

Ever thought about liquid cooling the PCs?

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Liquid cooling may make your components run cooler but I think the same amount of heat still exits your PC.

They still use the same energy either way. And watercooling, generally, does not cool below ambient.

Peltier coolers (the most common alternative) are powered devices, which use more watts, which generates more heat.

I was actually thinking about making a custom exhaust tube to run from the back of each PC to a main pipe that goes out of my house, vents all the heat outside and i can pull it in during the winter to heat the house.

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Originally Posted by Fursphere

Depending on pipe length, you might need inline fans though.

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exactly what I was thinking

I did something similar to this for my first setup. Enclose all of the CPUs and then vent the air either outside in the summer or inside in the winter. Pretty much turned off the heater in the winter - had a 1200 watt heater going full blast all of the time anyway :)

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Originally Posted by Nitro

I was actually thinking about making a custom exhaust tube to run from the back of each PC to a main pipe that goes out of my house, vents all the heat outside and i can pull it in during the winter to heat the house.

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I thought about doing the exact same thing! When I stop renting and get a place that is. Renting sucks. Which reminds me I should be doing my weekly on-line check of the area.

Brad - how bad are your power bills?

5 Boxing I don't think I ever went over $250 a month for my entire house.

10 Boxing and all of the hardware upgrades and cooling system upgrades...well ... should be around $300 - $350 once I put some power saving measures in place....

Timing the AC unit and setting my monitors to sleep, etc.

The monitors alone run $50 a month to run 24/7!

My wife and I only pay about $160 a month and we run 7-9 computers 24/7

I guess electricity in the NW is alot cheaper, we live right next to Seattle.

Here in Texas, power isn't a LOT more expensive, we just run the A/C a whole lot more. Those 100-105 days are a bitch.