TL;DR
A 7,500-watt generator running at 50% load burns 0.8-1.2 gallons of propane per hour. On a standard 20-lb BBQ tank (4.7 gallons), that's about 4-6 hours. On a 100-lb tank (23.5 gallons), you get 20-30 hours of runtime at 50% load.
Propane vs Gasoline: Fuel Economics for Generator Backup
Propane is the preferred fuel for standby generators because it doesn't degrade in storage (gasoline goes bad in 3-6 months) and produces fewer engine deposits. The tradeoff is energy density: propane contains about 91,500 BTU per gallon vs gasoline's 114,000 BTU, so you need more fuel volume for the same runtime.
Fuel consumption depends primarily on load level, not generator size. A generator at 25% load uses roughly 30-40% less fuel than at 75% load. For budgeting, assume 50% load (the most efficient operating point for fuel-to-electricity conversion).
Top picks for this size
DuroMax XP10000E 10,000-Watt Gas Powered Portable Generator - Electric Start, Whole Home Backup Power, Transfer Switch Ready, RV & Emergency Ready #ad
★★★★☆ 4.6 · 666+ · $1560
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Champion Power Equipment 100177 8.5-kW Home Standby Generator with 50-Amp Outdoor-Rated Automatic Transfer Switch #ad
★★★★☆ 4.6 · 57 · $3649
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Generac 6864 XD5000E 5000-Watt Diesel-Powered Portable Generator - Ideal for Emergency Backup Power and Job Sites - Reliable Power for Demanding Applications - CARB Compliant #ad
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Pulsar 10, 000W Dual Fuel Portable Generator with Switch & Go Technology & Electric Start, PG10000B16 Non-Carb Approved #ad
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Pulsar 5,250W Dual Fuel Portable Generator with Switch and Go Technology, PG5250B #ad
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Westinghouse 5000 Peak Watt Super Quiet Portable Inverter Generator, Remote Electric Start with Auto Choke, Wheel & Handle Kit, RV Ready, Gas Powered, Parallel Capable #ad
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Honda Power Equipment EU3000IS 3000W 120V Portable Home Gas Power Generator #ad
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Generac Guardian 10kW Home Standby Generator with 100 Amp Transfer Switch - Automatic Whole House Backup Power for Storms, Emergencies, and Outages, WiFi Enabled, Runs on Natural Gas or Liquid Propane #ad
★★★★ 4.2 · 38 · $4119
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Honda EB5000 5000 Watt Generator, Quiet 120/240V Gas Powered OSHA-Compliant Portable Generator for Construction Site or Backup Power Supply, Up to 10.5 Hour Run Time (EB5000XK3AN) #ad
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Westinghouse 9500 Peak Watt Home Backup Portable Generator, Remote Electric Start with Auto Choke, Transfer Switch Ready, Gas Powered, CO Sensor #ad
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Generac 7690 GP6500 6,500-Watt Gas-Powered Portable Generator - Powerrush Advanced Technology - Reliable Power for Emergencies and Recreation - 49-State Compliant #ad
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Champion Power Equipment 8125-Watt Electric Start Tri-Fuel Portable Generator with Free 3-Year Warranty #ad
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Pulsar 7,250-Watt Super Quiet Dual Fuel Inverter Generator with Remote Start #ad
★★★★ 4.2 · 113+ · $998
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Champion Power Equipment 9375-Watt Dual Fuel Portable Generator with Electric Start and Free 3-Year Warranty #ad
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WEN 5,600-Watt Dual Fuel Portable Generator with Wheel Kit, Electric Start, and CO Watchdog (DF5600X) #ad
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AIVOLT 8000W Dual Fuel Inverter Generator, Super Quiet Electric Start Portable Generator Gas Propane Powered for Home Backup, RV, Camping & Travel - CARB Compliant #ad
★★★★☆ 4.7 · 379+ · $1100
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Champion Power Equipment 9375-Watt Electric Start Dual Fuel Home Backup Portable Generator with and CO Shield #ad
★★★★★ 5 · · $1000
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Champion Power Equipment 12,500-Watt Electric Start Tri Fuel Home Backup Portable Generator with Free 3-Year Warranty #ad
★★★★ 4.2 · 33 · $1260
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Genkins 8000W Inverter Generator Outdoor Portable Generators Gas Powered Super Quiet with Electric Start Ideal for Home Backup, RV, Camping, Travel #ad
★★★★☆ 4.7 · 17 · $839
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Generac 8,000-Watt Gas-Powered Portable Generator - COsense Technology - Powerrush Advanced Technology - Power for Emergencies and Recreation - Electric Start - Orange/Black - 50 State Compliant #ad
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Generac 12,500 Starting Watt Tri-Fuel Portable Generator - Electric Start - Gas, Propane or Natural Gas - Home Backup, Jobsite, or RV - Quiet Operation - Long Runtime - 50-State Compliant #ad
★★★★☆ 4.6 · 26 · $1399
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WEN 6800-Watt Dual Fuel RV-Ready Electric Start Portable Inverter Generator with Fuel Shut Off and CO Watchdog for Electric Vehicle Backup (DF680iX) #ad
★★★★☆ 4.7 · 309+ ·
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Westinghouse 5000 Peak Watt Super Quiet Dual Fuel Portable Inverter EFI Generator, Remote Electric Start, Gas & Propane Powered, RV Ready, CO Sensor, Parallel Capable, CARB Compliant #ad
★★★★☆ 4.7 · 80 · $1249
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Westinghouse 7500 Peak Watt EFI Dual Fuel Home Backup Portable Generator, Remote Electric Start, Transfer Switch Ready, Gas and Propane Powered, CO Sensor, CARB Compliant #ad
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Westinghouse 8200 Peak Watt Tri-Fuel Portable Inverter Generator, Remote Electric Start, Transfer Switch Ready, Gas, Propane, Natural Gas, Low THD, Safe for Electronics, Parallel Capable, CO Sensor #ad
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Generac 12,500 Starting Watt Tri-Fuel Portable Generator, Electric Start, Gas Propane Natural Gas, COsense Carbon Monoxide Detection, 9.5 Hour Runtime, Home Backup Emergency, 49-State Compliant #ad
★★★★☆ 4.6 · 32 ·
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Champion Power Equipment 8500-Watt Wireless Remote Start Ultra Quiet Tri Fuel RV Ready Portable Inverter Generator with StartLINK, Free 3-Year Warranty #ad
★★★★ 4 · 3 · $1389
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Generac 10kW Home Standby Generator with 16 circuit transfer switch, cellular connectivity, easy to use, whole house power backup, smart outage solution #ad
★★★★☆ 4.6 · · $3896
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These Amazon-available picks meet the calculated spec. For region-specific or licensed contractor-installed options, consult a local professional. See our Disclaimers.
Propane Consumption by Generator Size and Load
- 5,000W generator at 50% load: ~0.6 gal/hr — 20-lb tank lasts ~8 hours, 100-lb tank ~39 hours
- 7,500W generator at 50% load: ~1.0 gal/hr — 20-lb tank ~5 hours, 100-lb tank ~24 hours
- 12,000W generator at 50% load: ~1.5 gal/hr — 20-lb tank ~3 hours, 100-lb tank ~16 hours
- 22,000W standby at 50% load: ~2.8 gal/hr — requires a 250-gallon tank for multi-day outages
Frequently asked questions
How long will a generator run on a 20-lb propane tank?
At 50% load, a 5,000W generator runs about 8 hours on a 20-lb tank. A 7,500W runs about 5 hours. A 12,000W runs about 3 hours. Always keep at least 2 spare tanks for storms.
Is propane or gasoline better for generators?
Propane: longer shelf life (indefinite), cleaner burning, lower maintenance. Gasoline: higher energy density, easier refueling during outages. Dual-fuel generators let you choose based on availability.
How much propane does a whole-house generator use per day?
A 22kW standby generator burns about 2.8 gal/hr at 50% load or roughly 67 gallons per day. A 500-gallon tank provides about 7 days of continuous operation. For multi-day outages, schedule off-hours to conserve fuel.