Capacitor Tester & Calculator
Safely discharge, test, and evaluate HVAC capacitors. Determine keep-or-replace status and calculate parallel capacitor combinations.
Safety Warning — Capacitors Store Dangerous Energy
Even after the system is powered off, capacitors can retain a lethal electrical charge. A charged capacitor can deliver a severe shock, cause burns, or damage equipment. Always discharge before testing or handling.
This tool is intended as a reference for qualified HVAC technicians. Do not attempt capacitor testing unless you are trained in electrical safety.
Capacitor Safety & Testing Checklist
Follow each step in order — from power isolation and safe discharge through visual inspection and capacitance measurement.
Capacitors store electrical energy that can cause serious shock or burns even after the system is powered off. Always discharge before handling.
Keep or Replace?
Enter the rated and measured capacitance to instantly determine if your capacitor is within spec (±6% industry tolerance).
From the capacitor label
From your multimeter
Replacement must match or exceed this voltage
Parallel Capacitor Combiner
Don't have the exact μF? Capacitors wired in parallel add together. Enter two values to see their combined capacitance.
Common HVAC Capacitor Values
| Application | Typical μF | Voltage |
|---|---|---|
| Condenser Fan Motor | 3–10 μF | 370/440 VAC |
| Blower Motor (PSC) | 5–15 μF | 370/440 VAC |
| Compressor (small) | 25–40 μF | 370/440 VAC |
| Compressor (large) | 40–80 μF | 370/440 VAC |
| Dual Cap (typical) | 35/5, 40/5, 45/5 μF | 440 VAC |
Replacement Rules
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Our goal is to provide the HVAC community with helpful resources. If you have ideas for new calculators, improvements to this tool, or technical suggestions, we'd love to hear them.