Soft starters and hard start kits both help an air conditioner compressor start, but they work in opposite ways. A hard start kit gives an aging compressor an extra boost of starting torque. A soft starter reduces the sudden surge of electricity a compressor draws at startup. Which one helps depends on the problem you are trying to solve.
What a hard start kit does
A hard start kit adds a start capacitor and relay that give the compressor extra torque for the first moment of startup. It can help older compressors that hum, trip the breaker or struggle to start in extreme heat. Hard start kit installation typically costs $795 to $1,200.
What a soft starter does
A soft starter controls how quickly power ramps up when the compressor starts, reducing the large inrush of current. Homeowners often consider them when running an A/C on a generator or when lights dim noticeably each time the system starts.
Signs your compressor is struggling to start
- A loud hum or buzz from the outdoor unit before it starts
- Lights flicker or dim when the A/C kicks on
- The breaker trips at startup
- The outdoor unit clicks on and off without running
Diagnose first
Starting problems can come from a weak run capacitor, a failing contactor or a compressor near the end of its life. A $150 to $450 capacitor replacement may solve the problem on its own. We diagnose first and recommend a start device only when it will actually help.
Related prices
| Service | Typical Price Range |
|---|---|
| Hard Start Kit Installation | $795–$1,200 |
| Capacitor Replacement | $150–$450 |
| Compressor Start Relay | $200–$500 |
Typical ranges for guidance only; your exact price is given in writing before any work begins. See our full price guide.