Is this calculation free and private?

Yes, 100% of calculations execute locally in your web browser. No inputs or personal data are stored or transmitted.

What does the Home Generator Sizing & Surge Wattage Calculator give me?

It works out Total Running Load, Peak Starting Surge Load, Recommended Generator Rating and Continuous 80% Safe Load Limit, updating live as you change the inputs.

Is my data uploaded anywhere?

No. The calculation runs in your browser with JavaScript — nothing you type is sent to a server or stored.

Does it work on a phone?

Yes. The layout adapts to small screens and needs no app or signup.

Home Generator Sizing & Surge Wattage Calculator

Calculate total running watts, motor startup surge wattage, and recommended portable or whole-house standby generator size in kW.

100% free
Private in browser
No signup
No watermarks

Refrigerator / Freezer Running Watts

Sump Pump 1/2 HP Running Watts

Well Pump or Window AC Running Watts

LED Lights, Router & Electronics Watts

Microwave / Coffee Maker Watts

Total Running Load (Watts)

5,200

Peak Starting Surge Load (Watts)

10,200

Recommended Generator Rating (kW)

10.2

Continuous 80% Safe Load Limit (Watts)

8,160

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About Home Generator Sizing & Surge Wattage Calculator

Calculate total running watts, motor startup surge wattage, and recommended portable or whole-house standby generator size in kW. Enter Refrigerator / Freezer Running Watts, Sump Pump 1/2 HP Running Watts and Well Pump or Window AC Running Watts and the tool works out Total Running Load, Peak Starting Surge Load and Recommended Generator Rating straight away. Everything runs in your browser, so your data never leaves your device.

How to use Home Generator Sizing & Surge Wattage Calculator

Enter Refrigerator / Freezer Running Watts, Sump Pump 1/2 HP Running Watts and Well Pump or Window AC Running Watts.
Adjust the remaining options (LED Lights, Router & Electronics Watts and Microwave / Coffee Maker Watts) to match your case.
Read Total Running Load, Peak Starting Surge Load and Recommended Generator Rating in the results panel — copy or download what you need.

Key features

Shows Total Running Load (Watts)
Shows Peak Starting Surge Load (Watts)
Shows Recommended Generator Rating (kW)
5 adjustable inputs, results update as you type
No signup, no limits

Frequently asked questions

Is this calculation free and private?: Yes, 100% of calculations execute locally in your web browser. No inputs or personal data are stored or transmitted.
What does the Home Generator Sizing & Surge Wattage Calculator give me?: It works out Total Running Load, Peak Starting Surge Load, Recommended Generator Rating and Continuous 80% Safe Load Limit, updating live as you change the inputs.
What do I need to enter?: Just Refrigerator / Freezer Running Watts, Sump Pump 1/2 HP Running Watts, Well Pump or Window AC Running Watts, LED Lights, Router & Electronics Watts and Microwave / Coffee Maker Watts. Every field has a sensible default you can start from.
Is my data uploaded anywhere?: No. The calculation runs in your browser with JavaScript — nothing you type is sent to a server or stored.
Does it work on a phone?: Yes. The layout adapts to small screens and needs no app or signup.

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