Can I use a higher voltage capacitor?

Yes. A higher voltage rating is usually acceptable and can improve reliability. Never use a lower voltage rating than the original requirement.

How close does the µF value need to be?

For motor run capacitors, stay very close to the rated value (commonly within ±5%). For many start capacitors, a wider tolerance may be acceptable, but matching the original value is still best practice.

Can I replace a capacitor with a different capacitance value?

Only if the circuit design allows it. In most repairs, changing capacitance changes behavior and can cause poor startup, overheating, noise, or instability. Match the original µF whenever possible.

What matters besides capacitance and voltage?

Temperature rating, ESR (for power supplies), ripple current rating, polarity, and physical size/mounting. These factors strongly affect lifespan and performance.

How do I size a capacitor if the original is missing?

Use equipment documentation, motor nameplate data, and application rules. If data is unavailable, use a calculator and then verify operation under load. For critical equipment, consult technical support before powering up.

Selection Guide

What Size Capacitor Do I Need?

Q: What size capacitor do I need?

It depends on the circuit type. For a replacement, match the original capacitance (µF) first, then use the same or higher voltage rating. For motors, match the nameplate or original part value closely.

The fastest safe method is: match the original µF value, keep the same capacitor type, and use the same or higher voltage rating. Then verify temperature, ESR/ripple requirements, and physical fit.

Use Motor Capacitor Calculator Convert Capacitor Values

Quick Selection Rules

Match capacitance (µF) first for replacements.

Use the same capacitor type (run, start, electrolytic, film, etc.).

Use equal or higher voltage rating, never lower.

Check polarity and mounting before installation.

For power supplies, verify ESR and ripple-current suitability.

For high-heat areas, choose higher temperature ratings.

What Must Match by Application

Application	Must Match	Safe Upgrade Options
Motor Run (HVAC / pumps / compressors)	µF value (very close), AC voltage class, continuous-duty type	Higher voltage rating if physical fit is acceptable
Motor Start	Start-cap µF range and duty type (intermittent start use)	Higher voltage rating if dimensions fit and specs match
Power Supply Filtering	Capacitance, polarity, minimum voltage, temperature rating	Lower ESR series, higher temperature rating, higher voltage
Audio / Signal Coupling	Capacitance and dielectric behavior for the design intent	Tighter tolerance or higher voltage where appropriate

If You Are Replacing a Failed Capacitor

1. Read the original label: capacitance, voltage, temperature, and type.
2. Confirm whether it is polarized and ensure orientation is correct.
3. Match the µF value and select equal/higher voltage.
4. Verify mechanical fit: diameter, height, lead spacing, and mounting style.
5. Test and verify with meter readings before returning equipment to service.

If you are sizing for safety-critical, medical, aerospace, or high-energy systems, validate against applicable standards and manufacturer datasheets before installation.

Next Step Links

Motor Capacitor Sizing Calculator How to Test a Capacitor Shop Motor Capacitors Request Help From Specap