# how much wattage can a household can provide?

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### #1 niulinfeng

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Posted 27 May 2013 - 04:20 PM

hi, everyone, I am a newbie in lighting, so I have a very basic question to ask : how much wattage can a household can provide?

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### #2 David Mullen ASC

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Posted 27 May 2013 - 04:43 PM

I'm talking about U.S. power (60 Hz AC, 240V/120V) for a moment here:

Household circuit breaker boxes usually break down the incoming power into 20A circuits, but more than one outlet in a room may share that circuit (and it's not always 20 amps / 20A, some are 15A, etc.)  So first thing is to look in breaker box and see how the power is divided up, and second is to mark every outlet in the house in terms of which circuit it belongs to.  You can do this by switching off every circuit except one and then plugging a lamp or circuit tester in each outlet until it lights up, and then marking every outlet for that circuit and the matching switch in the breaker box, then moving on to the next switch.

Watts = Volts x Amps (some people use the mnemonic "West Virginia" to remember that.)  Appliances are usually rated for 120V, so 120V x 20A = 2.4kW.  However, due to line loss over distance, amount of power you can run through a cord, start-up power, etc. most people round down to 20A allows 2kW, or 1kW per 10A.  But again, that's per circuit, not per outlet.  As a general rule, often outlets along the same wall might be using the same circuit.  Also, keep in mind that other appliances in the house may be drawing power on the same circuit -- refrigerators for example.

As for how many usable circuits there are in a house, it depends on the house.  Some older houses only have 10A and 15A circuits (and some use a fuse box, not circuit breaker boxes, so carry spare fuses for those) and don't have a lot of total power available.

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### #3 niulinfeng

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Posted 29 May 2013 - 04:22 PM

I'm talking about U.S. power (60 Hz AC, 240V/120V) for a moment here:

Household circuit breaker boxes usually break down the incoming power into 20A circuits, but more than one outlet in a room may share that circuit (and it's not always 20 amps / 20A, some are 15A, etc.)  So first thing is to look in breaker box and see how the power is divided up, and second is to mark every outlet in the house in terms of which circuit it belongs to.  You can do this by switching off every circuit except one and then plugging a lamp or circuit tester in each outlet until it lights up, and then marking every outlet for that circuit and the matching switch in the breaker box, then moving on to the next switch.

Watts = Volts x Amps (some people use the mnemonic "West Virginia" to remember that.)  Appliances are usually rated for 120V, so 120V x 20A = 2.4kW.  However, due to line loss over distance, amount of power you can run through a cord, start-up power, etc. most people round down to 20A allows 2kW, or 1kW per 10A.  But again, that's per circuit, not per outlet.  As a general rule, often outlets along the same wall might be using the same circuit.  Also, keep in mind that other appliances in the house may be drawing power on the same circuit -- refrigerators for example.

As for how many usable circuits there are in a house, it depends on the house.  Some older houses only have 10A and 15A circuits (and some use a fuse box, not circuit breaker boxes, so carry spare fuses for those) and don't have a lot of total power available.

Thanks for your explanation, sir! I am going to make a short film in my apartment, so I want to boost the lighting of my apartment by replacing the current lightbulbs with one 150W and two 200W bulbs. Just want to know if it is feasible.

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Posted 29 May 2013 - 04:31 PM

Generally, yes, you'll be ok, but you need to be careful with what you're putting it into as most things are only rated for 60w bulbs. That said in brief spurts you can be fine running a 150W in them. But you gotta keep an eye on it.

Another option would be baging something like a par 64 off of the ceiling to boost the overall ambience of the room and then keeping with the 60W bulbs and employing negative fill (black solids to take light away from the opposite side of the lamp lighting)

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### #5 Travis Gray

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Posted 30 May 2013 - 09:29 AM

Another option, while maybe not great because of color temperatures, are fluorescent bulbs. You can get a higher output light while still staying under what the socket is rated for, but just be careful and make sure the bulb you're trying to use can fit the fixture. I have a lamp I used as a practical and put a ~60w fluorescent bulb in it and it was just barely short enough to stay under the top of the shade.

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### #6 niulinfeng

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Posted 31 May 2013 - 03:34 PM

Generally, yes, you'll be ok, but you need to be careful with what you're putting it into as most things are only rated for 60w bulbs. That said in brief spurts you can be fine running a 150W in them. But you gotta keep an eye on it.

Another option would be baging something like a par 64 off of the ceiling to boost the overall ambience of the room and then keeping with the 60W bulbs and employing negative fill (black solids to take light away from the opposite side of the lamp lighting)

most lightings are rated for 60w bulbs. do u mean those bulb socket,sir?

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Posted 31 May 2013 - 03:35 PM

Yes, as in most lamps you buy at stores, at least here in the US.

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### #8 niulinfeng

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Posted 31 May 2013 - 05:42 PM

Yes, as in most lamps you buy at stores, at least here in the US.

Can i get away with this limit by buying bulb sockets that support more power output?

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### #9 David Mullen ASC

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Posted 31 May 2013 - 07:38 PM

Sure you can rebuild a lamp with heavier gauge wire and a porcelain socket but it would take some work... I put 150w, even 250w bulbs in regular lamps rated for 60w all the time, you just have to shut them off between takes to keep them from overheating.
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Posted 31 May 2013 - 10:36 PM

Exactly. Or what I do now that I have one, is run most that I can to a dimmer board (Dove Systems) and just have them dim them all down between takes.

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### #11 JD Hartman

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Posted 04 July 2013 - 07:59 AM

Most sockets, even the plastic ones in practical fixtures are rated for 600w, the problem is the heat from the bulb (globe, bubble, lamp) and its effect on the fixture wiring.  Especially true of ceiling fixtures in practical locations.  That's why most ceiling fixtures and table lamps will have a caution sticker stating maximum wattage.

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