Central Air Conditioner LRA Surge Table by Tonnage and SEER2 Rating (2026)
Compressor locked-rotor amps (LRA) determine the peak surge watts required to start your central air conditioner. Modern high-efficiency SEER2 units draw lower running amps but still require soft-starters to tame inrush surges.
01 Understanding LRA on Condenser Data Plates
Every outdoor central air conditioner condenser features an aluminum data plate stamped with RLA (Running Load Amps) and LRA (Locked Rotor Amps).
To calculate peak surge wattage, multiply LRA by 240 volts. A 3.5-ton condenser with an LRA of 79 amps requires 18,960 starting watts without soft-starter intervention.
- LRA represents instantaneous locked-rotor starting current.
- Multiply LRA by 240 volts to calculate starting surge wattage.
- Soft-starters reduce factory LRA ratings by up to seventy percent.
02 LRA and Surge Reference Table
Review our standardized engineering table comparing stock compressor inrush against soft-starter equipped performance.
Installing a Micro-Air EasyStart drops inrush surge across every single tonnage category.
| A/C Tonnage | Typical LRA | Stock Surge Watts | With Soft-Starter | Running Watts |
|---|---|---|---|---|
| 2.0-Ton | 48 Amps | 11,520W | 3,800W | 2,100W |
| 2.5-Ton | 58 Amps | 13,920W | 4,600W | 2,500W |
| 3.0-Ton | 73 Amps | 17,520W | 5,200W | 3,100W |
| 3.5-Ton | 79 Amps | 18,960W | 5,900W | 3,600W |
| 4.0-Ton | 96 Amps | 23,040W | 7,100W | 4,200W |
| 5.0-Ton | 115 Amps | 27,600W | 8,500W | 5,200W |
- Locate the LRA rating on your outdoor condenser data plate.
- Soft-starters drop 3-ton to 4-ton inrush down to manageable 5kW-7kW levels.
- Modern SEER2 compressors still produce high locked-rotor spikes.
Frequently Asked Questions
Q: Where is the LRA rating located on my air conditioner?
The LRA number is stamped on the metal data rating plate located on the outdoor condenser cabinet, usually near the electrical service disconnect.
Q: Why is starting surge so much higher than running wattage?
When stationary, the compressor motor has zero back-electromotive force, allowing maximum electrical current to flow through copper windings until rotation begins.