Transfer Switch Size Calculator
Find the right transfer switch size based on your generator and home electrical needs.
Enter your generator's running (rated) watts
Your Recommendation
Recommended Transfer Switch Size
30 Amp
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Note: This is a general recommendation. For a complete assessment, consult a licensed electrician who can evaluate your specific electrical system.
How to Size a Transfer Switch
Choosing the correct transfer switch size is crucial for safe and effective backup power. Here's what you need to consider:
Match Your Generator Output
Your transfer switch should match your generator's output capacity. A common formula:
- Watts ÷ Volts = Amps
- Example: 7,500W ÷ 240V = 31.25A → Use a 30A transfer switch
Consider Your Electrical Panel
The transfer switch should not exceed your main panel's capacity. Most homes have 100A, 150A, or 200A service.
Common Transfer Switch Sizes
| Switch Size | Generator Range | Typical Use |
|---|---|---|
| 30 Amp | 5,000 - 7,500W | Portable generators, essential circuits |
| 50 Amp | 10,000 - 12,000W | Large portable or small standby generators |
| 100 Amp | 15,000 - 22,000W | Whole-house standby generators |
| 200 Amp | 22,000W+ | Large homes, service entrance rated |