Compression Lugs for Solar Farms, Utility PV and Battery Storage
Sep 29, 2026
A utility solar site is a lug job at every stage: strings into combiners, combiners into inverters, inverters into AC collection, collection into the substation, and on hybrid sites, battery containers into everything. Each stage has a different conductor and therefore a different lug. Get the lug family right at takeoff and the EPC does not spend the last month of the job chasing hot spots with an IR camera.
Stage by stage
Strings and combiners
Module strings run on PV wire (UL 4703), tinned copper, 8 to 10 AWG, terminated with MC4 connectors at the modules and landed on fuse holders or terminal blocks in the combiner. Combiner output to the inverter is typically 4/0 through 500 kcmil copper or aluminum. Lugs: tin plated copper compression lugs for copper, AL9CU dual rated mechanical or aluminum compression for aluminum. Tin plating matters outdoors and on tinned PV wire.
Inverter DC inputs
Central and string inverters land DC on bus pads or terminal lugs. Long barrel two-hole lugs are the usual spec on 350 kcmil and up, sized to the inverter manufacturer's pad drilling. Check the inverter manual for the lug listing it requires; some call out compression only, no mechanical.
AC collection
Inverter AC output through the collection system is where aluminum shows up: XHHW-2 or USE-2 aluminum in 500 to 1000 kcmil. Never land aluminum in a copper-only lug. Use AL9CU listed connectors or aluminum compression lugs with the joint compound and torque the manufacturer specifies. Copper pigtails through splicer reducers are a common transition at the switchgear.
Substation and grounding
Ground grid, equipment grounds and the fence bond use bare copper with irreversible compression grounding connectors and two-hole lugs on ground bars. Ground rods and clamps at every array block. NEC 690.47 and Article 250 govern; utility interconnection specs often add exothermic or irreversible below grade.
Battery storage (BESS)
Battery containers and rack strings run fine strand battery cable, often 2 kV DLO class, on 2/0 to 500 kcmil. This is flex and battery lug territory. A standard Class B lug on a Class K battery cable is the number one termination defect on storage sites. See the DLO lug guide.
Spec checklist for solar EPCs and installers
| Item | Spec |
|---|---|
| Copper lugs | UL 486A/B, tin plated, long barrel two-hole on 4/0 and up, NEMA drilling |
| Aluminum conductor | AL9CU dual rated mechanical, or aluminum compression with compound; torque per 110.14(D) |
| PV wire terminations | Tin plated lugs; MC4 1000 V or 1500 V at the module end; Class B or C conductor |
| BESS and inverter DC | Flex or battery lugs listed for fine strand; heavy wall; tin plated |
| Grounding | Irreversible compression connectors, ground bars, rods and clamps |
| Outdoor exposure | Tin plating throughout; no bare copper lugs on aluminum or in corrosive air |
| Tools | 12 ton hydraulic with dies by index; die must match the lug's marking |
Why installers stock Conversions Tech
- The cross is on the page. Solar specs name Burndy or ILSCO. Every lug page shows the equivalent, so the submittal goes through without a call.
- Volume with stock. Two-hole 500 and 750 kcmil, MC4 connectors by the thousand, ground bars and rods, all stocked with same-day shipping on in-stock items.
- One source for DC and AC. MC4, PV wire, fuses and disconnects, lugs, grounding, aluminum transitions.
- Trade pricing and terms. Contractor and distributor pricing on POs; net terms through the credit application; container programs for repeat volume.
Product families are on the solar and EV installer supply page. For a site takeoff, send the single line and conductor schedule to CS@ConversionsTech.com.
Related: Cable type to lug cross reference · Wind and hydro lugs · Trade accounts
