Weekly digest #184: price changes in copper

Copper hit another rough patch this week. LME settled near $4.85/lb on Friday, up roughly 6% from the prior Monday, with COMEX tracking close behind. If you bid jobs three weeks ago on $4.55 wire, your margin just walked out the door. Here is what changed, what it means for your next pull, and how to protect the next bid.

What moved the market

Three things stacked up. Chilean mine output came in light again on the April production reports. Chinese grid spending guidance ticked higher on the Q1 release. And the dollar softened against the basket, which always lifts metals. None of these are one-day shocks, so the spike has legs into May.

Distributors are not eating the difference. Most of the majors pushed price sheets effective Monday, with THHN, XHHW, and bare copper grounding all moving 4 to 7%. MC cable and SER followed by Wednesday. Aluminum building wire stayed flat, which matters for the substitution conversation below.

Watch these three numbers each Monday morning before you submit bids:

• LME copper spot settle (London close)
• COMEX front-month future
• Your distributor's posted price sheet date

Where you feel it on the job

Service entrance work takes the biggest hit. A 200A residential service with 4/0 copper SER from the meter to the panel just got noticeably more expensive than it was in March. Same story on 3/0 and 250 kcmil feeders for commercial subpanels. If you priced a panel change a month ago and have not pulled material yet, recheck the ticket.

Branch circuit work hurts less in absolute dollars but adds up across a tract. A 2,400 sq ft house with the usual mix of 14 and 12 AWG runs is maybe $80 to $140 heavier than it was four weeks ago, depending on your distributor.

If your bid is older than 14 days and material is not on site, call your supply house and lock pricing in writing before the customer signs. A two-line email confirmation has saved more jobs than I can count.

The aluminum substitution question

With copper up and aluminum flat, the feeder substitution conversation comes back. NEC 310.16 and Table 310.16 still govern. For a 200A service, 4/0 copper at 75°C gets you 230A; you need 250 kcmil aluminum at 75°C for the same 205A column reading, and most AHJs will sign off on it for dwellings under 310.12 which permits 4/0 aluminum SER for 200A dwelling services specifically.

The catch is terminations. Verify the lugs at both ends are AL9CU or CU/AL rated per NEC 110.14. Anti-oxidant compound is not optional on aluminum terminations even when the lug listing does not strictly require it. Torque to the manufacturer spec on the label, not from memory, and recheck after 24 hours under load when you can.

• NEC 310.12: dwelling service and feeder ampacity table for aluminum
• NEC 110.14(A) and (B): termination and splicing requirements
• NEC 110.14(D): torque requirements per listing

Bidding adjustments that hold

Three changes that work in a rising market. First, shorten your bid validity language to 10 days on copper-heavy work. Most customers accept it once and never push back. Second, separate material and labor on the proposal so a copper escalator clause is easier to add without renegotiating the whole number. Third, build a 3 to 5% material contingency into anything over 30 days out.

If you run service work, consider stocking your most-used SER, MC, and THHN in 250 ft and 500 ft master coils when prices dip. The carrying cost is real but a 5% swing on a $4,000 wire order pays for a lot of shelf space. Track your turn rate so you do not end up sitting on inventory that ages out.

Price your next 30 days of pulls off your current cost basis, not last month's. The wire on the truck cost what it cost; the wire you order tomorrow is the new number.

Code refreshers worth a minute

A few articles that come up often when copper prices push crews toward shortcuts. Do not let the budget pressure walk you past the code book.

1. NEC 250.122: equipment grounding conductor sizing. Upsizing ungrounded conductors for voltage drop requires proportional EGC upsizing. This gets missed when crews spec heavier copper to "future-proof" a run.
2. NEC 310.15(B): ampacity adjustment for conduit fill and ambient. Squeezing one more circuit into an existing raceway to save a wire pull rarely pencils out once you derate.
3. NEC 408.4(A): circuit directory legibility. If you are reusing an existing panel on a remodel to dodge a service upgrade, the directory still has to be current and accurate.

What to watch next week

The May 1 distributor price sheets will tell you whether this is settling or extending. Watch for any movement on aluminum building wire, since flat aluminum is the only thing keeping the substitution math attractive. If aluminum starts to climb in sympathy, the calculus changes fast.

The Q2 copper inventory reports out of LME and Shanghai drop mid-month. If warehouse stocks fell again, expect another leg up. If they recovered, you may get a small reset in late May. Either way, the bids you write today should assume the current number, not the one you wish were still posted.