Data on cost effectiveness of 14 vs 12 gage NM in residential or other wiring systems

[iblittljn]

Question: Does anyone know of any study or analysis or have data that compares the cost effectiveness of using a 12 gage NM wiring method compared to 14 gage in residences or other locations that the 14 gage NM wiring method can be used?
Background: Since the resistance of 14 gage wire is about 60% higher than 12 gage but 12 gage costs 50% more ($90 per 1000 ft), there may be a monetary advantage to using 12 gage instead of 14 gage due to Ohm's law. Lighting systems are usually wired with 14 gage NM but could be wired with 12 gage, saving energy. Lots of devices operate 24/7/52 - DVR, chargers, instant-on sound systems, etc. So over the 30+ year life cycle of a residential cable plant, would there be a cost savings to the owner if 12 gage wire were used rather than 14 gage? Any hard data to support either position would be helpful. Thanks.

 

[electrofelon]

Question: Does anyone know of any study or analysis or have data that compares the cost effectiveness of using a 12 gage NM wiring method compared to 14 gage in residences or other locations that the 14 gage NM wiring method can be used?
Background: Since the resistance of 14 gage wire is about 60% higher than 12 gage but 12 gage costs 50% more ($90 per 1000 ft), there may be a monetary advantage to using 12 gage instead of 14 gage due to Ohm's law. Lighting systems are usually wired with 14 gage NM but could be wired with 12 gage, saving energy. Lots of devices operate 24/7/52 - DVR, chargers, instant-on sound systems, etc. So over the 30+ year life cycle of a residential cable plant, would there be a cost savings to the owner if 12 gage wire were used rather than 14 gage? Any hard data to support either position would be helpful. Thanks.

Just something to think about: More wire resistance will LOWER the power consumed on a circuit with resistive loads.

 

[junkhound]

Just anecdotal, but a retired electrician I worked with on Habitat houses said the copper savings is 'trivial' compared to the manhours savings in routing and wire pull and box fill impact it there are more than a few light fixtures. Copper savings is simply another plus if you save an hour or more of time for 250 ft.

When I was young and copper cheap, used 12 AWG for everything.
Last house I wired ALL light fixtures were 14 AWG, SO much easier and faster to run, and with fluorescent and LED lights nowadays, there is relatively little current to calculate into the equation.

Some folks even use 14 AWG/15A breakers for everything except the kitchen and shop outlets (or electric heat), not may loads in a modern house anymore reach even 15A except kitchen and shop, if there is a shop.

Of course, WA and CO now have legal MJ, so maybe in those states everything has to be 20A (or more) to support the gro lights <G>.

 

[kingpb]

Question: Does anyone know of any study or analysis or have data that compares the cost effectiveness of using a 12 gage NM wiring method compared to 14 gage in residences or other locations that the 14 gage NM wiring method can be used?
Background: Since the resistance of 14 gage wire is about 60% higher than 12 gage but 12 gage costs 50% more ($90 per 1000 ft), there may be a monetary advantage to using 12 gage instead of 14 gage due to Ohm's law. Lighting systems are usually wired with 14 gage NM but could be wired with 12 gage, saving energy. Lots of devices operate 24/7/52 - DVR, chargers, instant-on sound systems, etc. So over the 30+ year life cycle of a residential cable plant, would there be a cost savings to the owner if 12 gage wire were used rather than 14 gage? Any hard data to support either position would be helpful. Thanks.

The problem is that you are comparing installed cost (first cost) to operational costs. The builder wants to do things the cheapest possible way, the Owner will have to live with the higher operating costs; of which the builder could care less.

 

[kwired]

Just something to think about: More wire resistance will LOWER the power consumed on a circuit with resistive loads.

But energy required to complete a specific task will remain the same - so time to complete the task starts to factor in there, and your watthour meter still will register same watthours to complete that task - and that is ultimately what you pay for. Now installation cost can be some factor but 14 vs 12 AWG is not really that big of a cost difference unless it is a very long circuit run - but then you do complicate it more with voltage drop.

 

[electrofelon]

But energy required to complete a specific task will remain the same - so time to complete the task starts to factor in there, and your watthour meter still will register same watthours to complete that task - and that is ultimately what you pay for. Now installation cost can be some factor but 14 vs 12 AWG is not really that big of a cost difference unless it is a very long circuit run - but then you do complicate it more with voltage drop.

True. A task that requires a specific amount of energy like heating a tank of water to X degrees would result in the watthour meter "seeing" the energy lost in a smaller conductor. My argument was based on something like an incandescent bulb with the assumption that the person doesnt notice the slight decrease in brightness and put in a bigger bulb or turn up the dimmer that may have otherwise been turned down a bit. Of course resistive loads are becoming a thing of the past and I assume CFL's and LED lights are constant power devices regardless of voltage (within reason)?

 

[kwired]

True. A task that requires a specific amount of energy like heating a tank of water to X degrees would result in the watthour meter "seeing" the energy lost in a smaller conductor. My argument was based on something like an incandescent bulb with the assumption that the person doesnt notice the slight decrease in brightness and put in a bigger bulb or turn up the dimmer that may have otherwise been turned down a bit. Of course resistive loads are becoming a thing of the past and I assume CFL's and LED lights are constant power devices regardless of voltage (within reason)?

Well voltage drop will result in losses no matter what, as it is a resistive load though usually small enough that it is often ignored.

When it comes to say space heating - you aren't losing much unless the wiring is outside the space being heated, as the loss is still given up to the heated space.

 

[Jraef]

...Since the resistance of 14 gage wire is about 60% higher than 12 gage ...

Let's start here. While this statement is true the actual values of energy costs involved are often so infinitesimal that it becomes ludicrous to give them serious consideration. It's the same false logic often used by "energy saver" scam artists selling capacitors.

Consider a load rated 100W, I don't care if it's an incandescent or a string of LED lamps, the total load is 100W and let's call it all resistive (just for argument's sake). With 14 gauge wire the losses in a 100ft run are roughly .00100017W. With 12 gauge wire, the losses are .0100011W. So the DIFFERENCE in actual power consumption is only .0000006W! If that load was to run 24/7/365, the difference in energy consumed in a YEAR would amount to .37Wh, or .00037kWHr. At let's say 11 cents per kWh, that comes to a whopping 0.04 CENTS of energy cost per year. So now lets say this involves 100 such circuits., so 10,000 feet of wire running who knows how many lights, 24/7/365. $4.00 per year.

Spurious argument even though TECHNICALLY less energy consumption.

Oops, off by a factor of 10 on the resistance value, and some calc errors (divided by instead of subtracted from 1). Redoing...

 

[kwired]

Let's start here. While this statement is true the actual values of energy costs involved are often so infinitesimal that it becomes ludicrous to give them serious consideration. It's the same false logic often used by "energy saver" scam artists selling capacitors.

Consider a load rated 100W, I don't care if it's an incandescent or a string of LED lamps, the total load is 100W and let's call it all resistive (just for argument's sake). With 14 gauge wire the losses in a 100ft run are roughly .00100017W. With 12 gauge wire, the losses are .0100011W. So the DIFFERENCE in actual power consumption is only .0000006W! If that load was to run 24/7/365, the difference in energy consumed in a YEAR would amount to .37Wh, or .00037kWHr. At let's say 11 cents per kWh, that comes to a whopping 0.04 CENTS of energy cost per year. So now lets say this involves 100 such circuits., so 10,000 feet of wire running who knows how many lights, 24/7/365. $4.00 per year.

Spurious argument even though TECHNICALLY less energy consumption.

Oops, off by a factor of 10 on the resistance value, and some calc errors (divided by instead of subtracted from 1). Redoing...

I think with your last comment - you caught what I noticed, and I never did any calculations, I just noticed you had higher losses for the 12 AWG then you did for the 14 AWG, but assuming you maybe just misplaced the decimal point.

 

[Jraef]

Phone rang and the edit timed out too. Then I discovered my time values were way off too. Just not my day I guess.

OK Redo...

Consider a load rated 100W, I don't care if it's an incandescent or a string of LED lamps, the total load is 100W and let's call it all resistive (just for argument's sake). With 14 gauge wire the losses in a 100ft run are roughly .17539W. With 12 gauge wire, the losses are .1103W. So the DIFFERENCE in actual power consumption is only .0651W! If that load was to run 24/7/365 (8760 hours), the difference in energy consumed in a YEAR would amount to 570Wh, or .57kWHr. At let's say 11 cents per kWh, that comes to a whopping 6.26 CENTS of energy cost per year.

Still spurious...

 

[kwired]

Phone rang and the edit timed out too. Then I discovered my time values were way off too. Just not my day I guess.

OK Redo...

Consider a load rated 100W, I don't care if it's an incandescent or a string of LED lamps, the total load is 100W and let's call it all resistive (just for argument's sake). With 14 gauge wire the losses in a 100ft run are roughly .17539W. With 12 gauge wire, the losses are .1103W. So the DIFFERENCE in actual power consumption is only .0651W! If that load was to run 24/7/365 (8760 hours), the difference in energy consumed in a YEAR would amount to 570Wh, or .57kWHr. At let's say 11 cents per kWh, that comes to a whopping 6.26 CENTS of energy cost per year.

Still spurious...

Now there are times when voltage drop is critical, but for say a resistance heater - you would almost never recover any extra installation cost via increased efficiency in conductor losses.

 

[iblittljn]

Thanks for the great comments. The 100 watt post is valid as a "per unit" example (if math is correct) but the trouble I am having is with magnitude: Its 9 PM. I am sitting in my home office with 2 light bulbs (CFL) on, my laptop and charger are on, refrigerator is running, TV is on, DVR is recording a show I want to watch later and wife is on her computer. Sound system is in standy instant-on mode, her computer is attached to a laser printer ready to print, I am charging up batteries for my impact driver and saw for a job tomorrow. The outside porch lights are on as are the lights on the garage. And our Internet connected router is running. Our fiber optic telephone interface unit is on, connecting us to the telphone network and charging its batteries periodically. I believe our smart phones are on chargers (differnt phone models - different chargers). Something tells me there are several amps being drawn through a cable system permitted to use the 14 gage NM wiring method. Thanks.

 

[Jraef]

Thanks for the great comments. The 100 watt post is valid as a "per unit" example (if math is correct) but the trouble I am having is with magnitude: Its 9 PM. I am sitting in my home office with 2 light bulbs (CFL) on, my laptop and charger are on, refrigerator is running, TV is on, DVR is recording a show I want to watch later and wife is on her computer. Sound system is in standy instant-on mode, her computer is attached to a laser printer ready to print, I am charging up batteries for my impact driver and saw for a job tomorrow. The outside porch lights are on as are the lights on the garage. And our Internet connected router is running. Our fiber optic telephone interface unit is on, connecting us to the telphone network and charging its batteries periodically. I believe our smart phones are on chargers (differnt phone models - different chargers). Something tells me there are several amps being drawn through a cable system permitted to use the 14 gage NM wiring method. Thanks.

So all of those loads are on the exact same circuit with 14ga wire?

Of course they're not, I'm making a point. If the issue of conductor size was all-important, why not just use 10ga wire? Or why not embed the walls of the house with 1/4" x 4" solid copper bus bar? Or why not use silver wire?

Because it's not PRACTICAL for the infinitesimal gain in efficiency you attain, that's why. 14ga wire is fine for the vast majority of loads you can use in a household given that we like to use different circuits so that all of the lights don't go out when a breaker trips. We are going to divide the loads up anyway, so why use more copper than necessary?

 

[iblittljn]

So all of those loads are on the exact same circuit with 14ga wire?

Of course they're not, I'm making a point. If the issue of conductor size was all-important, why not just use 10ga wire? Or why not embed the walls of the house with 1/4" x 4" solid copper bus bar? Or why not use silver wire?

Because it's not PRACTICAL for the infinitesimal gain in efficiency you attain, that's why. 14ga wire is fine for the vast majority of loads you can use in a household given that we like to use different circuits so that all of the lights don't go out when a breaker trips. We are going to divide the loads up anyway, so why use more copper than necessary?

14 gage cable is indeed fine for the vast majority of loads you can use in a household. However, it may not be the most cost effective over time for the owner. (That's what I am trying to determine). The issue of conductor size is selection between the 14 gage NM or 12 gage NM wiring method based on power loss. It is certainly not all important. 10 gage NM cable could not be used because there are no devices made for that cable size (receptacles, switches etc). I do suspect its acquisition cost would not benefit such installations. And it would be very difficult to thread thru walls etc. The other options you identified are not permitted wiring methods by the NEC. Thanks.

 

[kwired]

14 gage cable is indeed fine for the vast majority of loads you can use in a household. However, it may not be the most cost effective over time for the owner. (That's what I am trying to determine). The issue of conductor size is selection between the 14 gage NM or 12 gage NM wiring method based on power loss. It is certainly not all important. 10 gage NM cable could not be used because there are no devices made for that cable size (receptacles, switches etc). I do suspect its acquisition cost would not benefit such installations. And it would be very difficult to thread thru walls etc. The other options you identified are not permitted wiring methods by the NEC. Thanks.

As has been pointed out the cost (dollars) in line losses is nearly something you can ignore. The performance issues from things that are adversely effected by voltage drop is a different story, and may be worth running a larger conductor to avoid those issues.

Things like dimming lights may be an issue for some and not hardly even noticed by others, but unless it is effecting life of the lamp, ballast, or other items, isn't really costing enough to be a concern.