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400 amp 3 phase panelboards, 208Y/120 and 480Y/277
A 400 amp three phase panelboard carries 144 kVA at 208Y/120 volts and 333 kVA at 480Y/277 volts. Public listings in November 2026 put a new 400 A Square D I-Line interior at about $1,900 to $2,300 before breakers and enclosure, and complete used panels at about $2,300 to $3,500. A stock 400 A Eaton panel ships in 1 to 2 weeks, a factory order in 5 to 7. We quote new, new surplus and used panelboards delivered, with the breakers you need.
400 A three phase panelboard or 400 A house service
A residential 400 A service is single phase 120/240 V and is built from load centers and a meter base. A 400 A three phase panelboard is a commercial and industrial item, built to UL 67, on a 208Y/120 or 480Y/277 V system. This page is about the second kind.
Voltage and the transformer each one needs
The voltage decides how much power the panel carries and what feeds it. At 208Y/120 a 400 A panel is 144 kVA, so a 150 kVA transformer carries it at full rating, delivering 416 A. At 480Y/277 it is 333 kVA, which takes a 500 kVA transformer for the full rating. A 300 kVA unit delivers 361 A at 480 V and is enough when the calculated load stays under that.
| System | kVA at 400 A | Transformer for full rating | Smaller unit and its amps |
|---|---|---|---|
| 208Y/120 V, 3 phase 4 wire | 144 | 150 kVA | 112.5 kVA, 312 A |
| 480Y/277 V, 3 phase 4 wire | 333 | 500 kVA | 300 kVA, 361 A |
Computed, kVA equals amps times volts times 1.732 divided by 1000.
Main breaker or main lug only
A main breaker panel has its own 400 A breaker and can serve as the disconnect. A main lug only panel, MLO, has lugs where the feeder lands and relies on a breaker upstream, usually in a switchboard or a separate disconnect. MLO interiors are the cheaper option in the listings below, a new Square D I-Line interior at under $2,300, while a new surplus I-Line interior with a 400 A main breaker listed at $3,250.
- Choose a main breaker panel when it is the service equipment or the first device after the transformer
- Choose MLO when it is fed from a switchboard breaker sized for it
- Check the short circuit rating. The I-Line HCP interior listed below carries 200 kA, branch panels are often far lower
Models you will see
These are the product families named in the listings and sources on this page.
- Square D I-Line, the HCP, HCN and HCJ interiors. Its breaker plug on jaws need no fasteners. The HCP32684 interior is rated 600 V AC, 400 A, 63 spaces and 200 kA, and fits a 42 in wide, 68 in high, 9.5 in deep box
- Square D NQ and NF. Tech Energy America describes NQ as the branch circuit panelboard and NF as the distribution panelboard
- Eaton Pow-R-Line, PRL1 through PRL4. Tech Energy America puts PRL-1 at 225 to 600 A and notes Eaton stock panels often ship at 65 kA without a surcharge
- Siemens P series, which Tech Energy America calls the industrial specification choice, with copper bus standard and lower stock in its region
Indoor or NEMA 3R
An outdoor panel needs a NEMA 3R enclosure. Tech Energy America adds $1,200 to $3,800 and 1 to 3 weeks of lead time for a NEMA 3R enclosure on a replacement job in Arizona. One of the used listings below is a 400 A Eaton PRL3A MLO already in a 3R outdoor box. Our NEMA enclosure chart explains each rating.
Public prices, November 2026
These are public asking prices from distributor and surplus listings read in November 2026. An interior is the bus and the frame only, without the box, the trim or the branch breakers, so a complete panel costs more.
| Item | Condition | Price | Seller |
|---|---|---|---|
| Square D I-Line HCP32684 interior, 400 A MLO, 63 spaces, 200 kA | New | $2,273 (list $2,706) | Standard Electric Supply |
| Square D I-Line HCP23594 interior, 400 A MLO, 45 spaces | New | $1,932 | Zoro |
| Square D HCP interior, 400 A 208/120 V with LGA36400 main, 30 spaces | New surplus | $3,250 | Brilliant Breakers |
| Square D I-Line panel, 400 A 480/277 V, MJA36400 main, 30 spaces | Used | $3,500 | Brilliant Breakers |
| Eaton PRL3A panel, 400 A 480Y/277 V MLO, 18 circuits, NEMA 3R | Used | $2,275 | Brilliant Breakers |
Asking prices from the sources listed below, not our prices. Freight is extra on every listing.
Installed cost
Tech Energy America publishes $11,000 to $18,500 to replace and relocate a 400 A, 84 circuit Eaton PRL panelboard, with 4 to 6 weeks from order to finish. That covers the panel, labor and permit on a commercial job in Arizona, and an arc flash study and labels add $1,800 to $4,500.
Lead times
Tech Energy America lists a 400 A, 84 circuit Eaton PRL-1 at 1 to 2 weeks from its stock and 5 to 7 weeks from the factory, and Square D NQ panelboards from 100 to 400 A at the same week from stock and 3 to 4 weeks from the factory. Switchboards from 800 A take 10 to 14 weeks or more. A used or new surplus panel ships once it is tested and packed.
What to send for a quote
- Voltage and system, 208Y/120 or 480Y/277, 3 phase 4 wire
- Main breaker or main lug only, and top or bottom feed
- Number of spaces and the branch breaker schedule if you have one
- Short circuit rating required at the panel
- Indoor or NEMA 3R outdoor, surface or flush mount
- Copper or aluminum bus if specified
- New, new surplus or used, and the delivery ZIP code
Common questions
How much does a 400 amp 3 phase panel cost
In November 2026 public listings put a new 400 A Square D I-Line interior at about $1,900 to $2,300 without breakers or enclosure, a new surplus interior with a 400 A main at $3,250, and complete used 400 A panels at $2,275 to $3,500. Installed, Tech Energy America quotes $11,000 to $18,500 to replace and relocate an 84 circuit 400 A panel.
What size transformer for a 400 amp 3 phase panel
At 208Y/120 V the panel is 144 kVA, so 150 kVA covers its full rating. At 480Y/277 V it is 333 kVA, so 500 kVA covers it, while a 300 kVA unit delivers 361 A and is enough when the load is below that.
What is the difference between MLO and main breaker
A main breaker panel has its own main breaker and can act as the disconnect. A main lug only panel has lugs instead and is protected by a breaker upstream. MLO costs less and is used when a switchboard feeds the panel.
How many kVA is a 400 amp 480 volt panel
333 kVA at full rating, three phase. At 208 V the same 400 A is 144 kVA.
How long does a 400 amp panelboard take to get
Tech Energy America lists 1 to 2 weeks for a stock 400 A Eaton PRL-1 and 5 to 7 weeks from the factory. Used and new surplus panels ship once tested.
Can a 400 A panelboard go outdoors
Yes, in a NEMA 3R enclosure. Tech Energy America adds $1,200 to $3,800 for the 3R enclosure on a replacement job.
Related pages
Sources
- Standard Electric Supply, Square D HCP32684 I-Line panelboard interior
- Zoro, Square D HCP23594 panelboard interior 400 A main lug
- Brilliant Breakers, Square D HCP interior 400 A 208/120 V with LGA36400 main
- Brilliant Breakers, Square D I-Line panelboard 400 A 480/277 V MJA36400 main
- Brilliant Breakers, Eaton PRL3A panelboard 400 A 480Y/277 V MLO NEMA 3R
- Tech Energy America, Commercial panelboard upgrade, cost and lead times
- Tech Energy America, Switchgear vs panelboard
Market figures are public asking prices and published industry figures, dated where the source gives a date. They are not our prices. A quote from us is a delivered price for a specific unit.