PickMyWatt

Portable Generator Wattage Calculator

Calculate the right portable generator size for your home, RV, or job site. Select appliances below to see total wattage, NEC-compliant sizing, and estimated fuel costs.

🏠
Home Backup
Power essential appliances during outages — fridge, lights, WiFi, and a window AC.
🏕️
Camping & RV
Run an RV AC unit, mini fridge, and charge devices off-grid.
🔧
Job Site
Run power tools like circular saws, drills, and compressors at a remote job site.
🎉
Outdoor Events
Power speakers, lighting, and food prep equipment for tailgates or parties.
W
NEC 80% Rule: Per NEC 210.20(A), continuous loads (running 3+ hours) should not exceed 80% of rated capacity. Your 5,000W generator safely handles 4,000W continuous load.

Your appliances

Running W = normal draw · Starting W = motor startup surge · Contruns 3+ hours (NEC continuous load) · Non-Contshort duty

W
W
W
W
W
W
W
W
3 appliances · 1,850W running
Generator Size
5,000W
watts
Load Status47%
NEC Load: 1,888WUsable: 4,000W
Refrigerator150/600WCont
Microwave (1000W)1,200WNon-Cont
Washing MachineMAX SURGE500/1,200WNon-Cont

Fuel Cost Estimate

gal
Price
$$/gal
Hours/Day8h
Diversity?75%
Avg Load?
2%
Rate: 0.075 gal/kW/hr. Sources: Generac, Honda, US EIA
Per Hour
$0
Per Day
$0
Per Month
$5
Calculation breakdown
Base Load: 150W ÷ 5,000W = 3%
Avg Load: 3% × 75% = 2%
Fuel/hr: 5.0 kW × 0.075 × 2% = 0.01 gal/hr
Cost/hr: 0.01 × $3.00 = $0.02/hr
Cost/day: $0.02 × 8h = $0/day
Cost/month: $0 × 30 = $5/mo

PickMyWatt.com

Portable Generator Wattage Calculator

Your Generator
5,000
watts
Load: 47%
Continuous
150W
Non-Cont
1,700W
Starting Surge
700W

Selected Appliances

Refrigerator150/600W
Microwave (1000W)1,200W
Washing MachineMAX SURGE500/1,200W
Fuel Cost Estimate
Per Hour
$0.02
Per Day
$0
Per Month
$5
gasoline

Calculated with PickMyWatt.com

NEC Article 220 Compliant

Calculation Standard: Based on NEC Article 220 load calculation principles. Continuous loads (>3 hours) sized at 125% per NEC 210.20(A). Non-continuous loads use only the largest expected simultaneous load.
Data Sources: Energy Star, DOE, Manufacturer specs (Generac, Honda, Champion, Kohler)

How to Choose the Right Portable Generator

A portable generator is the most versatile backup power option for homeowners, renters, contractors, and outdoor enthusiasts. Unlike standby generators, portable generators can be moved, stored in a garage, and used for multiple purposes — from home backup during outages to powering tools at a job site.

Portable Generator Sizes: What Do the Watts Mean?

Portable generators range from small 1,000W units to large 15,000W+ models. The wattage rating tells you how much electrical load the generator can handle. Using our calculator above, you can select your specific appliances and get an exact NEC-compliant recommendation.

Generator SizeTypical UseCan Run
2,000-3,500WCamping, tailgating, small essentialsFridge, lights, phone charger, fan, TV
3,500-5,000WHome backup essentials, RVAbove + window AC, microwave, sump pump
5,000-7,500WExtended home backup, job siteAbove + well pump, multiple appliances, power tools
7,500-10,000WMajor home backupMost home circuits including electric water heater
10,000-15,000WNear whole-house, large job siteEverything except central AC and electric dryer simultaneously

How We Calculate Portable Generator Size

Our calculator uses NEC Article 220 methodology:

  1. Continuous loads (3+ hours: fridge, lights, pumps) sized at full wattage
  2. Non-continuous loads (microwave, tools, hair dryer) — only the largest counts
  3. Apply the 80% rule per NEC 210.20(A)
  4. Account for starting surge from motor-driven appliances

Portable vs Inverter vs Standby: Which Do You Need?

FeaturePortableInverterStandby
Price$400-$3,000$500-$4,000$3,000-$15,000+
Wattage Range3,000-15,000W1,000-7,600W7,500-150,000W
Noise Level65-80 dB50-65 dB60-70 dB
Power Quality5-15% THD<3% THD5-10% THD
Auto StartNoNoYes

Frequently Asked Questions

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References & Sources