The allowable ampacity for 2/0 AWG Aluminum SER cable is 135 amps when terminated in standard 75°C residential panel lugs. For 2/0 AWG Copper SER, the allowable ampacity is 175 amps under the same 75°C termination conditions. While the individual conductors inside SER cable often carry a 90°C insulation rating, the National Electrical Code (NEC) strictly limits the final usable ampacity based on the temperature rating of the equipment terminations, not just the wire insulation.
This reference guide provides the exact NEC Table 310.16 values for 2/0 Service Entrance Round (SER) cable, explains how ambient heat and bundling modify those base numbers, and covers the edge cases that standard ampacity charts leave out.
The 2/0 SER Ampacity Reference Table (NEC Table 310.16)
SER cable typically contains two hot conductors, one neutral, and one bare equipment grounding conductor. The insulated conductors are usually XHHW-2 or THHN/THWN-2, which are rated for 90°C in dry locations. However, to use this table correctly, you must understand the three temperature columns:
- 60°C Column: Used for older equipment, specific appliance wiring, or when the termination temperature is unknown or explicitly marked 60°C.
- 75°C Column: The default governing column for almost all modern residential and commercial panelboards, breakers, and lugs rated 100A and above.
- 90°C Column: Used exclusively as the starting point for calculating derating factors (ambient temperature or conduit fill). The final derated value is then compared to the 75°C column, and the lower of the two becomes your legal ampacity.
| Conductor Material | 60°C Column (Amps) | 75°C Column (Amps) | 90°C Column (Amps) |
|---|---|---|---|
| Copper (Cu) | 145A | 175A | 195A |
| Aluminum (Al) / CCA | 115A | 135A | 150A |
Bookmark Quick-Jump: If you are wiring a standard 150-amp residential subpanel feeder using 2/0 Aluminum SER, your governing ampacity is 135A (75°C column). If you are using 2/0 Copper for a high-load continuous feeder, your governing ampacity is 175A.
Which Column Applies to Your Installation?
The most common mistake DIYers and junior electricians make is looking at the 90°C column (150A for Aluminum) and assuming they can safely land that wire on a 150-amp breaker. Under NEC Article 110.14(C), the temperature rating of the circuit is determined by the lowest rated component in the chain. Because standard panelboard lugs and breaker terminals are tested and listed for 75°C, the 75°C column governs your final breaker sizing.
How Derating Rows Modify the Base Value
The 90°C column exists so you have a higher baseline to apply penalty multipliers (derating) before comparing the result to the 75°C termination limit. Two main factors trigger derating for SER cable:
- Ambient Temperature: If you run 2/0 Al SER through a hot attic. According to NEC Table 310.15(B)(1), an ambient temperature of 110°F (43°C) requires a correction factor of 0.87. You multiply the 90°C baseline (150A) by 0.87, resulting in 130.5A. Because 130.5A is lower than the 75°C termination limit (135A), your new maximum ampacity drops to 130.5A.
- Current-Carrying Conductors Bundled Together: SER cable contains three current-carrying conductors (two hots, one neutral if it carries unbalanced load or harmonic currents). If you pull multiple SER cables through the same bored hole or conduit sleeve, you must apply the bundling adjustment factors in Table 310.15(C)(1). Four to six current-carrying conductors require an 80% multiplier.
In both scenarios, you calculate the penalty using the 90°C column, but you can never exceed the 75°C column value for the final overcurrent protection device.
What the Table Cannot Tell You (Edge Cases & Code Limits)
An ampacity chart assumes ideal conditions: a maximum of three current-carrying conductors, an ambient temperature of 86°F (30°C), and standard residential loads. Here is what the table leaves out that will fail an inspection if ignored.
The 83% Dwelling Service Rule (NEC 310.12)
If you are using 2/0 Aluminum SER as the main service entrance conductors for an entire single-family dwelling, NEC 310.12 allows you to size the conductors at 83% of the service rating. For a 150-amp service, 150A × 0.83 = 124.5A. Since 2/0 Al is rated 135A at 75°C, it is perfectly legal for a 150A dwelling service. However, 2/0 Aluminum is not large enough for a 200-amp dwelling service (which requires a minimum of 166A, pushing you to 4/0 Aluminum). Note: This 83% rule applies only to the main service conductors supplying the entire dwelling, not to subpanel feeders.
Voltage Drop Over Distance
Ampacity tables do not account for voltage drop. If you are running 2/0 Aluminum SER to a detached garage subpanel 250 feet away, a 130-amp load will cause a voltage drop of roughly 5.2% on a 240V circuit. This exceeds the NEC's recommended 3% maximum for feeders (found in Informational Note to NEC 310.15). For runs over 150 feet at high loads, you must upsize to 1/0 or 2/0 Copper, or 4/0 Aluminum, regardless of the base ampacity table.
Physical Bending Radius and Conduit Fill
2/0 SER is thick, stiff, and difficult to manipulate. NEC Article 339 dictates that SER cable must not be bent to a radius less than five times the diameter of the cable. Furthermore, while SER can be run through bored holes in framing, if you must transition it through a sleeve into a wet location or underground conduit, the conduit must be sized generously (typically 2-inch PVC minimum for a single 2/0 SER cable) to prevent jacket tearing during the pull.
Frequently Asked Questions About 2/0 SER Ampacity
Can I use 2/0 aluminum SER for a 200-amp subpanel?
No, not for the feeder conductors. While the subpanel itself can be rated for 200 amps (acting as a local disconnect), the 2/0 Aluminum SER feeding it is limited to 135 amps (75°C column). Under NEC 240.4(B) (the next-size-up rule), you could protect this wire with a 150-amp breaker, provided your calculated continuous and non-continuous load does not exceed 135 amps. If your actual calculated load approaches 200 amps, you must upgrade your feeder to 4/0 Aluminum or 2/0 Copper.
Does 2/0 SER cable need to be in conduit?
No. SER cable is specifically designed and listed to be run exposed or concealed inside walls without a raceway or conduit, similar to NM-B (Romex) but with a higher temperature rating and heavier gauge options. However, it cannot be buried directly in the earth. If you run it outdoors or underground, it must transition to individual THWN-2 conductors inside a rated conduit (like Schedule 80 PVC) or you must use a direct-burial rated cable like USE-2 or URD.
What size breaker do I use for 2/0 copper SER?
For 2/0 Copper SER, the 75°C ampacity is 175 amps. Since 175A is a standard breaker size listed in NEC 240.6, you can use a 175-amp breaker. If your specific panel manufacturer does not offer a 175A breaker (some residential lines jump from 150A to 200A), you must either downsize your breaker to 150A or use a panel that accepts 175A molded case breakers. You cannot use a 200A breaker on 2/0 Copper, as 175A does not qualify for the next-size-up rule to 200A.
Is the bare ground wire in 2/0 SER sized correctly for a 150A circuit?
Yes. Standard 2/0-2/0-2/0-1/0 SER cable includes a 1/0 AWG bare aluminum equipment grounding conductor. According to NEC Table 250.122, a 1/0 AWG aluminum ground is rated for circuits up to 200 amps. Therefore, the integrated ground in standard 2/0 SER is more than sufficient for a 135A to 150A feeder circuit.
