Weekly digest #214: price changes in copper

Copper is moving again

Copper hit another swing this week, and it is showing up in supply house quotes faster than usual. THHN, MC cable, and bare grounding conductors are all trending up. If you bid jobs three or four weeks ago at last month's pricing, your margin is already thinner than you think.

The driver is a mix of LME spot pressure and inventory tightness at the warehouse level. Distributors are repricing weekly, sometimes mid week. A few are quoting good for 24 hours only on bulk wire orders. That means the spool you priced Monday might cost more by Friday.

For service work, this matters less. For panel changes, feeders, or any job where you are pulling a lot of copper, build in a contingency or get the wire on site before you commit.

Where copper hits hardest on a typical job

Feeders and service entrance conductors are the obvious hit. A 200A residential service in #2/0 copper SER or parallel #4/0 in conduit can swing hundreds of dollars on a single house. Multiply that across a 12 unit job and it adds up fast.

Grounding electrode conductors per NEC 250.66 are another sneaky line item. A #4 copper GEC for a 200A service is small wire, but the bare copper price tracks raw spot tighter than insulated product. Same with bonding jumpers under 250.102.

• Service feeders sized per NEC 310.12 for dwellings
• GEC sized per NEC 250.66
• Equipment grounding conductors per NEC 250.122
• MC cable runs on commercial fitouts
• Motor branch circuits where copper is spec'd over aluminum

Aluminum is back on the table

When copper runs hot, aluminum starts to pencil out for feeders. NEC 310.12(A) already permits aluminum or copper clad aluminum for dwelling services and feeders supplying the main power. For a 200A service, #4/0 aluminum SER is the standard call.

The catch is terminations. Every lug, breaker, and splice in the path has to be rated for aluminum. Most modern panel main lugs are AL/CU rated, but verify before you assume. And use the listed antioxidant where the manufacturer requires it.

Tip from a 30 year journeyman: "I keep one tube of NoAlox in the van for every aluminum termination. Costs nothing, prevents callbacks, and the inspector sees it and moves on."

Bidding strategy when material is volatile

If you are quoting work more than two weeks out, separate material and labor on the proposal. State the material price is good for 7 or 14 days and subject to current invoice cost after that. Most commercial GCs accept this language. Residential customers need it explained, but they understand it once you do.

Another option is to buy and stage the wire on signed contract, before the job actually starts. Storage is cheap, repricing is not. If you have the cash flow, this locks your number.

1. Quote with a material expiration date in writing
2. Pull current copper spot before sending any bid over $5k in wire
3. Buy long lead items at contract signing, not at job start
4. Track your wire cost per foot in a spreadsheet, not in your head
5. Recheck spool pricing the morning of any pull over 500 feet

What to actually do this week

Walk your truck and your shop. Count what you have. If you are under a 1000 foot spool of #12 THHN black, white, and green, top off now. Same for #10 and #6. The small stuff moves fast and the per foot price is climbing in step with the bulk wire.

Call your supply house and ask for their current price sheet, dated. Some reps will quote off last month's sheet if you do not push. Get the dated quote in writing or on email so you have it for the next bid.

If you have open quotes that are more than 14 days old and the customer has not signed, send a revised number. Do not eat the swing because you did not want to make the call.

Tip: "Price every bid off today's wire cost, not last week's. If you lose the job over $80 in copper, you were not going to make money on it anyway."

Code reminders that save copper

NEC 310.12 simplifies dwelling service conductor sizing. For a 200A service, you can use #2/0 copper or #4/0 aluminum. Some electricians still default to the older 310.16 ampacity table and oversize the wire. Read the article, use the right table, and stop buying copper you do not need.

NEC 240.4(D) sets the small conductor rule. #14 copper protects at 15A, #12 at 20A, #10 at 30A. There are exceptions in 240.4(E) and (G) for specific applications like motor circuits and tap conductors. Know the exceptions and you can right size instead of upsizing out of habit.

NEC 250.122 sizes the equipment grounding conductor based on the overcurrent device, not the phase conductor. A #12 EGC is fine on a 20A circuit even if you upsized the phase conductors for voltage drop. Check 250.122(B) for the proportional upsize rule when it applies.