Weekly digest #64: price changes in copper

Copper is moving again. If you bid jobs three weeks ago with wire pricing from last quarter, you are losing money right now. This digest covers what is happening with copper, how to hedge your material exposure, and the NEC citations that determine when you can and cannot substitute.

Where copper sits this week

COMEX copper closed at roughly $4.85 per pound this week, up from $4.12 four weeks ago. That is an 18 percent jump in under a month. Distributor pricing on THHN, MC cable, and bare copper ground has already adjusted. Expect another bump when current distributor inventory clears.

The driver is a combination of Chilean mine disruptions, grid buildout demand in Asia, and inventory drawdowns at LME warehouses. None of these resolve in the next 60 days. Plan accordingly.

• #12 THHN stranded: up roughly 14 percent since March
• #6 THHN: up roughly 16 percent
• 250 kcmil THHN: up roughly 19 percent
• 1/0 bare copper ground: up roughly 17 percent

Bid protection on open proposals

If you have proposals outstanding that are more than 14 days old, pull them back and rebid. Most commercial customers will accept a revised bid if you show them the distributor quote. Residential customers are harder, but a brief written note explaining the copper market shift usually lands.

For new proposals, add material escalation language. Cap the quote at 7 or 14 days, and include a clause that ties copper line items to the spot price on the day of purchase. If you cannot get the customer to accept escalation, shorten the quote validity window.

Tip from the field: screenshot your distributor's price sheet the morning you bid. If the job closes and copper has jumped, that screenshot is your proof when you renegotiate or change-order.

When aluminum is a legitimate substitute

Aluminum feeders and service conductors are code-compliant under NEC 310.3 and sized per NEC Table 310.16. For a 200 amp residential service, 4/0 aluminum SER replaces 2/0 copper SER and the material cost delta is substantial right now. Verify the terminations are rated AL-CU or AL9CU per NEC 110.14(A).

Aluminum branch circuits are a different story. NEC 310.3(B) permits aluminum down to #12, but most jurisdictions and inspectors will push back hard on aluminum branch wiring in dwellings because of the legacy failure history. Stick to copper on branch circuits 20 amp and under.

• Service entrance and feeders: aluminum is fine, check lugs per 110.14
• Grounded conductor in parallel sets: aluminum acceptable per 310.10(G)
• Equipment grounding conductors: aluminum permitted per 250.120, but not in damp locations or within 18 inches of earth per 250.64(A)
• Branch circuits in dwellings: copper only, practically speaking

MC cable versus pipe and wire

On commercial tenant improvements, the pipe and wire versus MC cable calculation shifts when copper jumps. MC still uses copper conductors, so the copper content is a wash. The savings come from labor and EMT elimination. When copper is high, the relative labor savings from MC pull ahead because you are eliminating less expensive steel and more expensive per-foot installation time.

Check your AHJ. NEC 330.10 permits MC in most occupancies, but some jurisdictions still restrict it in plenums unless it is specifically listed. NEC 300.22(C) governs plenum installations and you want MC-PCS or similar plenum-rated product.

Tip from the field: on a 10,000 square foot office fit-out, switching from EMT and THHN to MC typically saves 20 to 30 percent on labor. At current copper prices, that is real money.

Managing existing inventory

Walk your truck and your shop this week. Any copper wire sitting on shelves is worth more than it was 30 days ago. Do not bleed it into small change orders at old pricing. Track what you have, update your internal cost basis, and bill accordingly.

If you run a service van stocking program, audit the wire spool counts. Service calls where you replace a feeder or rewire a panel should be priced on replacement cost, not what you paid six months ago.

1. Count all copper inventory on trucks and in shop
2. Mark internal cost basis to current distributor replacement pricing
3. Update T and M rate sheets for material markup
4. Flag any open change orders that use old material pricing

Theft exposure is up

Copper theft tracks the spot price. Jobsite theft reports climb roughly two weeks behind a sustained price jump. If you have copper staged on a jobsite, especially ground bar, bus duct, or large feeders on a rooftop or remote pad, lock it down or stage smaller quantities.

Document serial numbers on reels when possible. File a police report the same day for any theft. Your insurance carrier will want the documentation and many policies have sublimits on copper theft that you should verify before you need them.

• Do not leave cut lengths of bare copper overnight on open sites
• Stage MC and THHN reels inside locked containers
• Photograph staged material at end of day
• Review your policy sublimits for copper loss