Generator sizing Last reviewed June 2026

What Size Propane Tank for a House Generator?

By the WhatSize editorial team 5 min read Standards-reviewed

TL;DR

A 7,500W portable generator needs a 20-100 lb propane tank (5-23 gallons). A 14-22kW whole-house standby generator needs a 250-500 gallon propane tank for multi-day runtime.

Looking for a different size? See What Size Generator for a 2,000 Sq Ft House? or browse all generator sizing guides.

Why Propane Tank Size Matters More Than You Think

Propane is one of the best fuels for generators — it never goes bad, burns cleaner than gasoline, and can be stored indefinitely. But propane tank sizing is often misunderstood. A generator's runtime depends on both the generator's load and the tank's capacity, measured in gallons or pounds.

For portable generators, LP conversion kits allow propane use with standard 20 lb grill tanks (about 4.7 gallons). A 3,500W generator running at 50% load burns about 0.8-1.0 gallons of propane per hour, giving you about 4-5 hours per 20 lb tank. For multi-day outages, you'd need multiple tanks or a larger 100 lb tank (about 23 gallons).

For whole-house standby generators, the propane tank needs to be permanently installed. A 14kW Generac at full load burns about 1.6 gallons of propane per hour. Over a 3-day outage, that's 115 gallons — requiring a 250-gallon minimum tank. A 500-gallon tank provides about 7-8 days of runtime at 50% load, which is the recommended safety margin for extended outages.

Top picks for this size

BEST OVERALL

DuroStar DS13000MX 13,000W Dual Fuel #ad

13,000W, Dual Fuel, Electric Start, Whole Home Backup

★★★★☆ 4.6 · 177+ ratings

Dual Fuel (Gas/Propane)13,000W PeakElectric Start

$899 approx

Check price

MID-RANGE

Westinghouse 5000W Dual Fuel Inverter #ad

★★★★☆ 4.7 · 19.3K+ · $949

Amazon

These Amazon-available picks meet the calculated spec. For region-specific or licensed contractor-installed options, consult a local professional. See our Disclaimers.

Propane Tank Sizing Guide by Generator Type

Portable 3,500W (Champion, WEN): 20 lb tank (~4.7 gal) gives 4-5 hours at 50% load. Stock 2-3 tanks for 24-hour coverage. Upgrade to 100 lb tank (~23 gal) for multi-day outages.
Portable 7,500W (Westinghouse, Generac GP): 100 lb tank (~23 gal) gives 10-14 hours at 50% load. Consider a 420 lb tank (~100 gal) for extended backup.
Standby 14kW (Generac 14kW): 250 gallon minimum tank — 3-4 days of runtime at 50% load. 500 gallon recommended for areas with frequent or long outages.
Standby 22kW (Generac 22kW): 500 gallon tank — 3-5 days at 50% load due to higher consumption (1.8-2.0 gal/hr). 1,000 gallon for coastal/hurricane areas.

Frequently asked questions

What size propane tank for a whole-house generator?

A 7,500W portable generator burns about 0.8-1.2 gallons of propane per hour at 50% load. A 14kW standby burns about 1.2-1.6 gal/hr. At full load, consumption roughly doubles. Always size your tank for the worst-case scenario — a winter ice storm that could last 3-5 days.

Can I use a BBQ propane tank with my generator?

Yes, if your generator has a dual-fuel or LP conversion kit. A standard 20 lb BBQ tank (4.7 gallons) works, but runtime is limited to 4-6 hours depending on load. For anything beyond a few hours, you need multiple tanks or a larger cylinder.

Is propane better than gasoline for generators?

Propane has three major advantages: it never degrades (gasoline goes bad in 6-12 months), it's cleaner burning (less maintenance, fewer carbon deposits), and it's safer to store (no spills, no fire hazard from vapors). The main downside is slightly lower power output and higher cost per unit of energy.