How Much Propane Does a Generac Generator Use?

In South Florida, it’s not only a question of “Will my generator run?” but “Will it last for the entire outage?” If you have a standby Generac generator that runs on liquid propane, you may be curious how much propane a generator uses and how long a Generac can run.

In general, a Generac whole-home generator typically burns 1 to 3 gallons of propane per hour, depending on the unit’s size and how much load it's actually carrying. For instance, a 22kW generator running at half load might use about 2 gallons of propane per hour, while one running at full load may surpass 3.5 gallons per hour.

This guide explores generator propane use at different loads so you can stay well informed and prepare for generator installation.

Propane Use Per Hour, by Generator Size

Before we share the table, you must understand fuel consumption equations. Fuel consumption equations are designed to convert the gas your generator uses (measured in cubic feet per hour or cubic meters per hour) into energy output (measured in BTUs (British Thermal Units) or megajoules).

To calculate fuel consumption for liquid propane:

• Multiply cubic feet per hour (ft³/h) by 2,500 to get BTU/h.
• Multiply cubic meters per hour (m³/h) by 93.15 to get megajoules per hour (MJ/h).

The figures in this table are based on standard Generac air-cooled generators in varying sizes.

* Data from Generac

** Values given are approximate

How Long Will Your Tank Last?

After you figure out your generator’s average hourly burn rate, you can estimate how many days a propane generator tank will last during an outage. It’s best to only count on about 80% of your tank’s rated capacity because propane tanks are never filled completely. The extra space is there to allow the liquid propane to expand safely in higher temperatures.

* Figures are estimates only. Actual run time depends on generator size, load, and outdoor conditions

Remember, the larger your generator is and the more you’re powering, the more fuel it will burn per hour. That’s why propane tank sizing is so important when buying a standby generator. Sizing the tank depends on your generator and family’s typical outage length. It’s also important to decide whether a natural gas vs. propane generator is ideal for your home. Most propane tanks are buried underground to maintain curb appeal.

Stretching Your Propane During a Long Outage

Hurricane outages in Florida can last from several days to over a week. There are a few helpful tips you can follow to meaningfully extend your propane supply.

• Run only the systems you need: Consider whether you need non-essential circuits running for systems like a second AC zone or pool pump. Whole-home generators let you cycle off non-essential systems during peak draw.
• Set your thermostat a couple degrees higher: By setting your thermostat higher than usual, you can still stay safe in hot weather but cut fuel use significantly.
• Stagger high-draw appliances: If you run the dryer, oven, and AC at the same time your generator will approach its full load threshold. Try to stagger the use of high-draw appliances to lower fuel usage.
• Keep up with routine maintenance: Regular maintenance keeps your generator well tuned for optimal performance vs. one that’s overdue for service.

Sizing a Tank for Hurricane Season

In South Florida, we recommend you size your propane tank around your longest realistic outage. If you can, most homeowners should plan for outages that require up to seven days of run time, since major hurricanes and tropical storms can knock the power out for more than the typical 48 hours.

Here’s a breakdown of common sizing guidelines:

• For small generators (under 15kW) with short outage expectations, a 120-gallon tank is usually suitable
• Mid-sized homes running a generator intermittently can typically use a 250-gallon tank
• 500-gallon tanks are the most common choice for whole-home generators in hurricane-prone areas
• 1,000-gallon tanks are suitable for larger homes or generators with heavy loads for extended periods

It’s critical to choose the right propane tank for your residential generator. A professional generator installer can make sure your unit is installed correctly and up to code. Reliable Power Systems will help size, install, and connect a propane tank to your whole-home generator to ensure you’re ready when the next storm hits.

Call us at (561) 408-5147 or book a free tank sizing consultation online!