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We recently built a house and added 3/4 conduit underground from outside the breaker box to the top of the driveway for a future project to add stone pillars with LED lights (example pictures below).

The distance from the box to the top of the driveway is 400-425 feet, with a junction at one post where the wire will run underground to the other post.

My electrician said he would recommend 10 AWG wiring to prevent voltage loss. OK, great. Then I priced 500' rolls of 10 AWG wire, and WOW it's expensive. Is there any cheaper way to get the power to the light fixtures? I've heard suggestions to use solar, but we don't get a lot of sunlight, so I'm not sure if that would work.

Any suggestions? enter image description here

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    Is there an imperative to do this project NOW? Everyone is building right now. So you are doing the equivalent of looking for the new Playstation right before Christmas, or finding a popular Beanie Baby. Prices are insane. May 10 at 1:20
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    The house is already built. We have the leftover rock veneer and the conduit is in place. It's just a matter of pulling the wire and building the stone posts. I don't know about your house, but what's not imperative to me is sometimes imperative to someone else. :-)
    – RetiredATC
    May 10 at 2:28
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    I thought you said cost was a factor, in which case "wait" is one way to solve it! May 10 at 3:38
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    I was just shocked (pun intended) at the cost of the wire. Like most people, if I can do a quality job and save some money too, that's the route I'm going to travel.
    – RetiredATC
    May 10 at 3:44
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    @RetiredATC copper is very expensive now. I had to buy a roll of NM 10/3 for something that couldn't really wait more than a month or I'd start accumulating a bunch of other costs. If it could wait without much cost, waiting would be my response to current prices.
    – cr0
    May 10 at 14:13

7 Answers 7

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14 AWG and LED lights. Practically no current so practically no voltage drop. Easy enough to get LEDSs that run on 240V, so half of practically no current at double the volts if you're overly concerned (I would not be.) Easy enough to get LEDs that operate on 85-277 volts, for that matter, which will make a lot of voltage drop no problem...12 amps on 14Ga copper, for 1033W delivered at 86.1V to an LED that will take 85V in (and make it hard to enter your too-bright driveway.) Need more power? Stick to the wide-range input and change the supply to 240V. 2472 W at 206V & 12A)

What is your electrician planning for, 1000 watt incandescent bulbs?

If you're dead-set on overdoing it, you have room to run 6 gauge aluminum, which will cost less than 10 Ga copper...

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    +1 because LED = low power = 14 AWG is fine. But as far as the aluminum in place of copper, at least some places (Montgomery County, MD) do not allow aluminum for branch circuits, and unlike "I only want to add one circuit to charge my EV", this is not a situation where "OK, put in a small subpanel and use copper for the last few feet" will work. May 10 at 0:57
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    Put an (absurdly) small weatherproof subpanel on the first driveway pillar... ;^)
    – Ecnerwal
    May 10 at 1:58
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    Yeah, that's a specific adaptation to avoiding a deluded local rule. Even if you wanted a general purpose outlet there and thus chose to use #6 Al, you could just use appropriate connectors to pigtail the Al to Cu wires that would fit your devices - unless you lived in a place with a deluded local rule saying you couldn't.
    – Ecnerwal
    May 10 at 2:50
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    Brilliant answer, not just the humorous aspects but the reminder that long standing rules of thumb can be broken, shattered, and in fact you don't even need thumbs. Let me add:. Solar plus batteries plus 12 V trickle charger, despite the distance 12V will work because you have all day to charge the batteries. You can use old phone wire you get for free and you don't even need the conduit, just shove it between the driveway and the curb
    – jay613
    May 10 at 9:20
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    ...OP already has conduit in place ;^)
    – Ecnerwal
    May 12 at 12:08
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Lights only? Anything.

It all pivots on the receptacle. If you never want a general-use 120V receptacle there, then any wire will do down to #14 copper. So you can price based on the cheapest wire of any size. Further you can energize it at 240V as discussed by Ecnerwal.

Receptacle? Voltage drop is no joke

If you ever might want a general-use receptacles, then you have a nightmare on your hands because the receptacle load can be as much as 15 amps but more typically 12A. Voltage drop at long distance is bad enough at 240V; at 120V it is four times worse. People often "spitball" voltage drop calculations and "give it a bump or two" and get the wrong answer.

I suspect that is what your electrician did: erroneously "rule of thumb'ed" it based on 240V not 120V since 2 size bumps is about right for 240V. However at 120V not nearly enough.

Here try this: 400' distance, 120V, 4% voltage drop tolerable and 12 amps actual load. 6 AWG copper for 3.53% drop. Holy crud, that's not going to work! Costwise.

We could go to #8 copper for 5.52% drop @12A but we're still breaking the bank.

My favorite secret weapon for saving money (and doing a quality job) is aluminum wire. It's not the "moral panic" some make it out to be. It got a bad name on small branch circuits because in the 1970s, two key rules were botched.

  • Use terminals rated for aluminum wire. Most large terminals are.
  • Torque the connections to spec using a torque wrench. (mind you, the science hadn't even come in on this until 2008, and that science pertained to copper connections. But it explains why things went wrong in the 70s.)

Meanwhile, heavy feeders have always used aluminum without trouble. First because the large terminals are rated for aluminum (typically made of aluminum) and second because electricians always used torque wrenches on those.

So, heavy feeder. #6 aluminum is ideal. It fits in 3/4" condut, voltage drop @12A will be 5.72% which is as good as we're going to fit in 3/4" conduit.

Now we need a lug rated for aluminum wire. For #6 wire, you can use the relatively inexpensive ILSCO "Mac Block Connector". This has a neat trick - the second port can accommodate up to four smaller copper wires. So you can attach three #14 for the run to the socket and lamps. And that's it!

The trick is finding it, especially since #6 and smaller must be natively black, white and green. It's not really a Home Depot thing - it's best to deal with local electrical supply houses. The internet is a flaming disaster for trying to purchase electrical equipment; it's low value for its weight, which makes it expensive to ship. As a result, most people quote the "I don't wanna ship it" price. The only reliable place for sensible pricing is an electrical supply house.

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  • Lots of people forget about aluminum. This is a perfect use case for al wire!
    – Scottie H
    May 10 at 21:27
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    I'm intrigued by "mind you, the science hadn't even come in on this until 2008, and that science pertained to copper connections. But it explains why things went wrong in the 70s." What was this new science? Does putting a precise amount of torque on electrical connections matter? How does it explain what went wrong with aluminum in 1970s? May 12 at 19:10
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What's the purpose of these lights? Are you

  • just illuminating the step for pedestrians in the dark?
  • Or is it all-night lighting?
  • is it for security?

If you just want people to not trip, I'd suggest one of these sensor LED lights on either side. They charge well enough, and only switch on for motion then stay on for about 2 minutes. The battery lasts at least 3 years and the units are cheap.

enter image description here


But I suspect you want to power the existing light fittings. In that case, I'd suggest getting a solar-powered security light that has a flat solar panel on a wire. These are intended so the lamp can go where it needs to, but the panel can be some distance away for better angle and insolation. Something of this design:

General image

There will be a lithium battery somewhere, probably behind the LEDs and not in the solar panel itself. I'd get two (maybe a third as a spare) and then open the unit.

Figure out the voltage it drives the LEDs at and see if you can get an LED lamp/bulb for your existing fixture that suits. If not, I'd look at rearranging the entire guts of the light fitting with the LEDs inside your existing housing, the motion sensor aiming toward the steps, and the solar panel in the best place for sunlight.

I know you said "you don't get a lot of sunlight" which suggests this area might be in shadow a lot. That's okay - modern solar panels will produce voltage even on cloudy days.

The upsides are overall price savings compared to the long run of mains cable, and its a completely autonomous independent system separate from your mains electrics.

Downsides, it needs effort on your part to make something nice-looking here, and there will be a solar panel hanging out somewhere. Perhaps angled on the capstone, or on the sunward face of the stone pillar.

Last resort is to replace the mains-powered pillar-topper fittings pictured with something designed to be solarised. Think nicer than those nasty garden-edge solar spike lights. Example: enter image description here

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    The OP's picture was "for example", so any of your solutions would work. In fact, any solution would work!
    – FreeMan
    May 10 at 11:37
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    I referenced this answer in a new question I just posted: diy.stackexchange.com/q/249035/4191
    – Tango
    May 10 at 17:17
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What's the cheapest way to wire these lights?

The right way, period.


"The cheap man pays twice" is thoroughly applicable here.

If you run anything other than a wire which is rated for 20A at that distance then you will just live with regret. If you cannot "afford" this then don't do the project yet. Wait for prices to come down, if ever.

You may not be thinking it but you will want a receptacle or two nearby for other seasonal decorations. You'll also end up wanting to plug in other things like a nearby bounce-house for kids birthday party, a leafblower, electric whatever power tool, etc...

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    The bouncy house does not go at the end of the long driveway near the road, the power tools are Lithium Battery Powered these days. Be sure to install rings so your guests can tie up their horses, and do it right by running a gas line for gas lights, you can't trust these new-fangled electric lamps - someone might leave a switch on with no bulb in place and you'll have electricity just flowing out of the socket getting everywhere..(credit to J. Thurber, of course).
    – Ecnerwal
    May 10 at 14:32
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    @Ecnerwal Yes, because it would be outlandish to tap into the middle of the conduit and have outlets closer to home or to throw a birthday party in the front of a house with 400 feet of front yard because their backyard is only 20 feet deep or to need an electric concrete mixer to pour a slab at the end of the walkway. Totally unrealistic!
    – MonkeyZeus
    May 10 at 15:26
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    @Ecnerwal: While I agree a bouncy castle is likely not going to be used at the end of a driveway and that most tools are battery powered these days, I have to agree, from experience, that once you have power there, at some point, you want to use it. As for running a new conduit with other wire to a center tap, that can be difficult. Once you put conduit in and cover it, re-trenching can be a major issue, especially if the conduit comes out from the house where bushes or flowers have probably been planted near the wall.
    – Tango
    May 10 at 17:22
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    @Ecnerwal: On the other hand, I learned, long ago, to think, "If I'm doing this, what will I want in the future?" and, before running 3/4" conduit for this, would have asked for help and numbers first AND planned on an outlet at the posts and considered outlets midway. I've just found having power 400' from the house is tempting. I have a post (for a Starlink dish) 800' from the house and, from the start, used heavier wire because I knew once I had power out there, I'd find other uses for it.
    – Tango
    May 10 at 17:24
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    Will I regret having done this the cheapest way possible? Yes, +1. The electrician is presuming two, upwards of, 250W bulbs and an eventual outlet. Which means bringing real power out there, not just a simple solution for some lights with zero future proofing.
    – Mazura
    May 10 at 19:59
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There is one important thing missing, what type and size of bulb. Assuming 2 100 W tungsten bulbs and allowing 7.2 Volt drop #12 would work fine on a 15 Amp circuit. You can use LED bulbs they will draw a lot less. Here is the calculator I used: https://www.southwire.com/calculator-vdrop If you want to get cheap use LED bulbs and with two of them drawing less then one amp you could use #14.The electrician gave you the best answer. With his solution you could also put a receptacle there for say a hedge trimmer etc. With my cheap solutions that would not work so good. You could also use aluminum wire. Whatever solution you pick pass it by your local inspector to see if it is OK with that person.

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    Just a quick look and I found a fixture that will hold 3 candelabra bulbs (below). 60W equivalent LEDs draw 5W apiece. Good for 14 AWG? lowes.com/pd/…
    – RetiredATC
    May 10 at 2:32
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    Two fixtures, 3 bulbs at 5W each per fixture, 30W total, a whopping 0.25A current at 120V. 450 foot distance, 14 AWG copper, 119.29V delivered at the end of the wire...
    – Ecnerwal
    May 10 at 3:07
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I'm unfamiliar with USA wiring codes, but in the UK everything goes away if you use 12V DC LED lighting. What you might spend on thicker cabling, you save by not having to employ an electrician.

How bright are you wanting? 12W of LEDs is the equivalent of a 100W light bulb. 1A at 12V. Resistance chart for 1000 ft of cable here. Resistance of 1000ft of 14 guage is 2.525 ohms, so around 1.25 Ohm for your distance. With 12V going in and a current draw of 1A (12W) you will drop 1.25V, and I'm pretty sure any 12V LED lamp or bulb will work on 10.75V. An LED won't run dim, it will draw a bit more current to compensate for a lower input voltage. If not, use a thicker gauge of wire.

Alternatively you might source a 13--14V PSU or adjustable PSU so at least 12V comes out. 12V is pretty nominal (it's Lead-Acid battery voltage, which is 13.6V fully charged and lightly loaded with a good battery on a warm day)

Your electrician may be correct for a supply which can deliver whatever your normal supply expectation is (15A?) without excessive voltage drop, but if you want to run LED lighting only, then tell him to install thinner cable and protect it with a low-current breaker. 1A (if you can get a 1A breaker!) will support 100W of lighting, which is a helluva lot of illumination using LEDs. If that's not permitted by your wiring codes ... back to 12V DC.

(Old Analogue security cameras were connected with co-ax cable for the signal and a 12V 1A power pair. Modern ones are power-over-Ethernet which is up to 15W supplied at 44V down Ethernet (26 gauge?) wires, still deemed safe for non-electricians, but you probably can't find any 44V LED lighting! )

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  • You forgot to double the distance because there are two 400ft wires involved.
    – user253751
    May 12 at 12:22
  • Oops, yes. So 2.5V drop or thicker cable.
    – nigel222
    May 12 at 12:36
  • It would be very easy to run 20-44V down the cable and put an 12V regulated supply at each post.
    – spuck
    May 12 at 18:12
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    Added bonus of doing it this way, there's no chance anyone can expect to use a mains-voltage outlet at the far end. Avoids the bouncy castle issue referenced above.
    – Criggie
    May 13 at 0:02
  • >An LED won't run dim, it will draw a bit more current to compensate for a lower input voltage. Depends on the drive circuitry. Many simple 12V LED bulbs just have a few LEDs and current-limiting resistor.
    – rsaxvc
    May 13 at 3:22
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I've heard suggestions to use solar, but we don't get a lot of sunlight, so I'm not sure if that would work.

I think this assumption has to be fundamentally addressed. Solar doesn't require direct sunlight to work. All it means is a lower power output and more panels.

Eyeballing the costs for 500 feet of copper wire throws some wild costs at $10k to $20k out. You could fit out a home with solar for a similar cost.

Use Monocrystalline

Monocrystalline panels have higher efficiency and work better in cloudy conditions. To keep costs down your best bet is to try to order direct from manufacturer or as near direct as possible (for example, aliexpress.com).

Calculate for Worst-Case

Your main calculations are going to be how much sun you get during winter periods on a day with the least amount of sunlight (worst case scenario), using the surface area of the panel plus rating to work out an estimate on power output, then working out the power demand of the lights, plus margins on energy conversion losses, to finally work out how many panels you'd need to keep it powered during operation.

Design the System to Reduce Losses

You'll want to aim for 12v LED lights (12v to avoid any upstep or downstep conversion power losses, LED for efficiency), coupled with a lithium ion battery (cheaper than lead-acid, smaller, doesn't require as big margins on discharge, better energy density), charge controller (MPPT is the most efficient, but you can get away with much cheaper PWM given it's a small project).

Use a Night-Sensor

To reduce power demands further, I'd also advise a light sensor to detect night-time/dark periods to turn the lights on when it is too dark to see, and off when there's natural sunlight to avoid wasting power, and pick batteries able to store a charge sufficient to cover the longest possible night during winter.

Put together these should easily allow you to implement a solar setup.

Other Options?

If you have a nearby river or stream, you could also use hydro. Wind turbines are expensive and intermittent but might be an option if you have good clearance for one.

If the system doesn't produce enough power, worst case scenario the lights don't turn on and you charge on a consecutive day. You can always add more panels and more batteries.

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    3x500 ft 14AWG copper Less than $200 with wire left over, and several of your suggestions are rather dubious (buying anything electrical from aliexpress, hydro power - yeah, every driveway has a handy year-round stream you can tap, and small scale hydro is terribly affordable - in your dreams, perhaps...)
    – Ecnerwal
    May 10 at 15:39
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    I recently had to run over 350' of 4/0 underground. Total cost for 3 AC wires (common and 2 legs) and a ground made of 2/0 was about $3,000. That includes conduit and j-boxes because I did it in multiple segments. That was wire purchased in April, so the pricing figures you give are seriously out of line.
    – Tango
    May 10 at 16:24
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    An RTG! Of course Plutonium is our friend!
    – Ecnerwal
    May 10 at 18:03
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    I do have a creek I can dam up, but it's 700' from the top of the driveway. Darn, that's going to be more wire. :-)
    – RetiredATC
    May 10 at 18:12
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    $10k, wtf? 500 feet of 10/3 is about $850. Where do you live?
    – MonkeyZeus
    May 11 at 1:15

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