What's the cheapest way to wire these lights that are 400' away at the end of the driveway?

Question

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?

Answer 1

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...

Answer 2

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.

Answer 3

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.

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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:

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:

Answer 4

What's the cheapest way to wire these lights?

The right way, period.

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"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...

Answer 5

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.

Answer 6

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! )

Answer 7

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.