Running a Generac standby generator on natural gas usually costs about $2 to $5 per hour. That equals roughly $60 to $120 for 24 hours of continuous operation.
A propane-powered model may cost $8 to $11 per hour when carrying a heavy whole-house load. Your final expense depends on generator size, fuel price, electrical demand, and outage length.
A 22kW model consumes about 200 cubic feet of natural gas per hour at half load and close to 300 cubic feet at full load. On propane, the same unit may use about 3 to 4 gallons per hour.
At Grounded Electric, head electrician Robert “Bobby” Mulholland and project manager Barret Abramow help Bergen County homeowners compare generator sizes, fuel options, installation requirements, and expected operating expenses.
Key Takeaways
- A 22kW Generac costs about $2 to $5 per hour on natural gas.
- Running one for 24 hours on natural gas usually costs $60 to $120.
- Propane can cost $8 to $11 per hour under heavier loads.
- A 22kW model uses about 200 to 300 cubic feet of natural gas per hour.
- The same model may consume about 3 to 4 gallons of propane per hour.
- A 500-gallon propane tank may support about 4 to 6 days of continuous use at sustained half-to-full load.
- Professional maintenance may cost about $300 to $600 per year.
- A complete standby generator installation may cost about $12,000 to $20,000, depending on the project.
- Most generators use less fuel in practice because household demand changes throughout the day.
Hourly and Daily Generac Generator Running Costs
If you are asking how much it costs to run a generator, the answer depends mainly on its fuel source, electrical load, size, and hours of operation.
A generator operating at half load consumes less fuel than one continuously powering air conditioning, electric heating, water heaters, kitchen appliances, and other large systems.
Cost to Run a 22kW Generac Generator
A 22kW Generac uses approximately:
- 203 cubic feet of natural gas per hour at half load
- 306 cubic feet of natural gas per hour at full load
- 3 gallons of propane per hour at half load
- 4 gallons of propane per hour at full load
Using typical residential fuel price assumptions, natural gas costs about $2 to $5 per hour. Propane operation costs about $8 to $11 per hour.
| Fuel and Load | Fuel Consumption | Hourly Cost | 24-Hour Cost |
|---|---|---|---|
| Natural gas at 50% load | About 203 ft³ per hour | $2 to $3 | $60 to $80 |
| Natural gas at 100% load | About 306 ft³ per hour | $4 to $5 | $90 to $120 |
| Propane at 50% load | About 3 gallons per hour | $8 to $9 | $190 to $215 |
| Propane at 100% load | About 4 gallons per hour | $10 to $11 | $240 to $265 |
Estimates use published 22kW consumption figures and assumed residential prices of roughly $12 to $16 per thousand cubic feet of natural gas and about $2.70 per gallon of propane. Local utility and delivery rates vary.
Moving a 22kW unit from half load to full load adds roughly $2 per hour to the natural gas expense. Over a three-day outage, the difference may reach about $140 to $215.
How Much Does It Cost to Run a Generac Generator Per Day?
A 22kW model running on natural gas generally costs:
- $60 to $80 per day at half load
- $90 to $120 per day at full load
Propane costs more. Continuous propane operation can exceed $200 per day, especially when the generator carries central air conditioning and other high-demand equipment.
Most homes do not maintain a constant full load—appliances cycle on and off, which often keeps actual daily consumption below the full-load estimate.
Fuel Type and Usage Costs
Your fuel source usually has the largest effect on hourly operating expenses.
Running a Generac Generator on Natural Gas
Piped natural gas is generally the least expensive fuel for a permanently installed standby generator.
The generator connects to the home’s gas line, eliminating the need to store or refill a separate fuel tank. This makes natural gas suitable for longer outages when utility service remains available.
A 22kW model consumes about 200 cubic feet per hour at half load and around 300 cubic feet per hour at full load. At common residential rates, that equals approximately $2 to $5 per hour.
The Generac natural gas generator cost per hour changes with your local utility rate and the percentage of the generator’s capacity being used.
For example, a generator using 203 cubic feet per hour costs about $2.84 per hour when natural gas costs $14 per thousand cubic feet. If the local rate rises to $18, the same amount of fuel costs about $3.65 per hour.
Check your latest gas bill to calculate a more accurate local estimate. You can also review this model-by-model natural gas consumption breakdown before calculating your hourly expense.
Running a Generac Generator on Propane
Propane works well for homes without natural gas service. It also gives the homeowner control over an on-site fuel supply.
A 22kW Generac may use:
- About 3 gallons per hour at half load
- About 4 gallons per hour at full load
At an assumed price of $2.70 per gallon, that equals approximately $8 to $11 per hour.
The cost of operating a Generac propane generator is usually higher than that of natural gas because propane is purchased and delivered by the gallon.
A 500-gallon propane tank is normally filled to about 80% of its capacity, leaving roughly 400 usable gallons. At a continuous burn rate of 3 to 4 gallons per hour, the tank may last about 4 to 6 days.
At $2.70 per gallon, filling 400 usable gallons would cost about $1,080 before delivery charges, taxes, or supplier fees. Actual tank-filling costs depend on local propane prices.
The tank can last longer when the generator operates intermittently or carries lighter loads.
Running a Generator on Diesel or Gasoline
Diesel standby generators are more common in commercial settings. Homeowners and property managers comparing fuel options can review this guide to choosing the best diesel generator for more information.
Diesel units provide dependable output but require on-site fuel storage and regular fuel-quality checks.
Gasoline is mainly used for portable generators. It requires manual refueling and is not the standard choice for an automatic whole-house system.
| Fuel Source | Typical Hourly Cost | Fuel Setup | Common Application |
|---|---|---|---|
| Natural gas | $2 to $5 | Connected to utility gas line | Automatic residential standby systems |
| Propane | $8 to $11 under heavier loads | On-site storage tank | Homes without natural gas service |
| Diesel | Depends on local diesel prices | On-site storage tank | Commercial and larger standby systems |
| Gasoline | Depends on generator size and pump prices | Manual refueling | Short-term portable backup power |
For a 22kW whole-house unit, switching from natural gas to propane can more than double the hourly fuel expense.
Costs by Generator Size and Type
Generac generators cost different amounts to operate based on their rated capacity, average load, fuel source, and local energy prices.
Larger generators can power more circuits, but their operating expenses depend on the electrical load they carry rather than capacity alone.
A properly sized generator running at a moderate load may use less fuel than an oversized unit operating inefficiently.
| Generator Size | Estimated Hourly Cost | Estimated 24-Hour Cost |
|---|---|---|
| 10kW to 14kW | $1.50 to $3.50 | $36 to $84 |
| 18kW to 20kW | $2 to $4.50 | $48 to $108 |
| 22kW | $2 to $5 | $60 to $120 |
| 24kW to 26kW | $3 to $6 | $72 to $144 |
These are planning estimates rather than fixed prices. Actual consumption depends on the exact model, household demand, local gas rate, and percentage of load.
How Much Does It Cost to Run a 24kW Generac Generator?
A 24kW Generac generally falls within the same operating range as other large residential standby models.
On natural gas, a planning estimate is about $3 to $6 per hour, or approximately $72 to $144 for 24 hours. The final amount depends on the exact model, household demand, and local gas rate.
Propane operation can approach or exceed $200 per day under a continuous heavy load.
Exact consumption varies between product generations and model numbers. Check the specification sheet for the exact unit rather than applying a 22kW consumption figure to every 24kW generator.
Cost to Run a Whole-House Generac Generator
A whole-house Generac generally costs about $60 to $150 per day on natural gas, depending on generator size, local rates, and electrical demand.
Propane costs can be higher and may exceed $200 per day during continuous heavy use.
Whole-house systems consume more fuel when they power equipment such as:
- Central air conditioning
- Electric water heaters
- Well pumps
- Clothes dryers
- Electric ranges
- Pool equipment
- Multiple refrigerators or freezers
Load-management modules can prevent several large appliances from starting simultaneously. This can lower peak demand and help the generator operate within its rated capacity.
Keeping a 22kW generator near half load instead of full load may lower natural gas spending from about $4 to $5 per hour to $2 to $3 per hour.
Factors That Affect Generator Running Costs
Electrical Load
The percentage of available capacity being used directly affects fuel consumption.
A generator supplying essential circuits may operate near half-load. A unit powering the entire electrical panel may approach full load when several major appliances run at once.
For a 22kW generator, the difference between half load and full load may equal about $1 to $3 per hour, depending on the natural gas rate.
During a 72-hour outage, that difference can add approximately $72 to $216 to the fuel bill.
Local Fuel Rates
Natural gas and propane rates differ by region.
Natural gas bills may also include delivery charges, taxes, and other fees. Propane prices can change based on order size, season, supplier, and delivery distance.
Use the effective rate shown on your bill rather than relying only on a national average.
A natural gas rate of $14 per thousand cubic feet puts a 203-cubic-foot hourly burn at about $2.84 per hour. At $18 per thousand cubic feet, the same generator costs about $3.65 per hour.
Generator Size
A larger unit can support more equipment, but it may consume more fuel.
Correct sizing matters. A generator should have enough capacity to handle starting loads without being much larger than the home requires.
Smaller standby models may cost about $36 to $84 per day on natural gas. A 22kW system may cost $60 to $120 per day, while a 24kW to 26kW unit may fall near $72 to $144 per day.
These ranges assume continuous use. Real-world daily costs may be lower when the generator operates at a lighter average load.
Maintenance and Servicing
Dirty filters, worn spark plugs, incorrect valve clearances, or neglected oil changes can affect performance.
Robert “Bobby” Mulholland recommends following the manufacturer’s service schedule and checking the generator after extended operation. Routine maintenance helps the unit start reliably and operate near its rated fuel consumption.
Professional standby generator maintenance typically costs $300 to $600 per year, depending on the generator’s size, service plan, and included parts.
Oil, filters, spark plugs, batteries, repairs, and emergency visits may increase the annual total. Reviewing typical generator maintenance costs can help you estimate the system’s recurring expense.
Installation Choices
Fuel-line sizing, electrical connections, transfer-switch configuration, and equipment placement can affect generator performance.
A whole-house standby generator installation often costs about $12,000 to $20,000. This range may include the generator, transfer switch, electrical work, fuel connection, permits, site preparation, and startup testing.
Complex gas line work, trenching, electrical panel upgrades, concrete pads, or difficult equipment access can increase the final cost.
Installation is separate from the hourly fuel expense. Homeowners should consider both the upfront generator installation cost and the long-term operating expense.
Scenario-Based Cost Examples
12-Hour Natural Gas Outage
A 22kW generator operating near half load may cost approximately:
$2 to $3 per hour × 12 hours = $24 to $36
24-Hour Natural Gas Outage
The same generator may cost:
$2.50 to $4.50 per hour × 24 hours = $60 to $108
This places a typical day near the $60 to $110 range.
Three-Day Natural Gas Outage
At a moderate average load:
$60 to $110 per day × 3 days = $180 to $330
Seven-Day Natural Gas Outage
A full week of continuous use at a moderate load may cost:
$60 to $110 per day × 7 days = $420 to $770
24-Hour Propane Outage
At 3 to 4 gallons per hour and $2.70 per gallon:
$8.10 to $10.80 per hour × 24 hours = $194 to $259
Three-Day Propane Outage
A sustained three-day propane run may cost:
$194 to $259 per day × 3 days = $582 to $777
These examples show why your fuel source and average load matter more than the generator’s maximum wattage alone.
How to Estimate Your Generator Costs
A generator running cost calculator can provide a starting estimate, but you can also calculate the expense manually.
Use this formula:
Fuel consumption per hour × Local fuel price × Hours of operation = Estimated running cost
Natural Gas Example
A generator uses 203 cubic feet per hour.
Your effective natural gas rate is $14 per thousand cubic feet.
- Convert consumption to thousands of cubic feet:
203 ÷ 1,000 = 0.203 - Multiply by the fuel rate:
0.203 × $14 = $2.84 per hour - Multiply by the outage length:
$2.84 × 24 hours = $68.16
Propane Example
A generator consumes 3 gallons per hour.
Propane costs $2.70 per gallon.
3 × $2.70 × 10 hours = $81
A Generac whole house generator cost calculator should use the consumption rating for your exact model. It should also allow you to enter your local fuel price and expected average load.
Total Cost of Owning a Generac Generator
Running costs are only one part of the total budget.
A homeowner may spend:
- $12,000 to $20,000 on equipment and installation
- $300 to $600 per year on maintenance
- $60 to $120 per day on natural gas during an outage
- $190 to $265 per day on propane under sustained load
For example, consider a generator installed for $15,000.
If maintenance costs $425 per year and the generator runs for three outage days per year at $90 per day, the estimated five-year cost would be:
- Installation: $15,000
- Five years of maintenance: $2,125
- Fifteen outage days: $1,350
- Estimated five-year total: $18,475
This example excludes repairs, financing, fuel-price changes, and equipment replacement.
Pros and Cons of Generac Standby Generators
Pros
- Automatic backup power during an outage
- Whole-house coverage when properly sized
- Natural gas and propane model options
- No manual setup when the power fails
- Support for essential electrical and HVAC systems
Cons
- Fuel expenses increase during extended outages
- Propane requires tank storage and refilling
- Larger units may consume more fuel
- Regular maintenance is required
- Installation adds a separate upfront expense
A standby generator can provide dependable backup power, but homeowners should plan for installation, maintenance, and fuel costs rather than focusing only on the equipment price.
A typical owner may spend $12,000 to $20,000 upfront, $300 to $600 per year on maintenance, and $60 to $120 per day of a natural gas outage.
Those comparing the full benefits and ownership expenses can also evaluate whether Generac generators are worth it for their home.
Frequently Asked Questions
How Much Does It Cost to Run a Generac Generator Per Day?
A 22kW Generac usually costs about $60 to $120 per day on natural gas. Propane operation under a heavy load may cost $190 to $265 per day.
How Much Does It Cost to Run a Generator for 24 Hours?
A large residential natural gas generator may cost approximately $60 to $120 for 24 hours. The same generator may cost more than $200 on propane under a sustained heavy load.
How Much Natural Gas Does a Generac Generator Use Per Hour?
A 22kW Generac uses approximately 203 cubic feet per hour at half load and 306 cubic feet per hour at full load. Consumption differs by model and capacity.
How Much Propane Does a Generac Generator Use Per Hour?
A 22kW unit uses approximately 3 gallons per hour at half load and 4 gallons per hour at full load.
Is It Cheaper to Run a Generac on Natural Gas or Propane?
Natural gas usually costs less per hour. Propane provides on-site fuel storage and is available in areas without utility gas service.
A 22kW model may cost $2 to $5 per hour on natural gas, compared with about $8 to $11 per hour on propane under heavier loads.
How Long Will a 500-Gallon Propane Tank Run a Generac Generator?
A 500-gallon tank contains about 400 usable gallons when filled to the standard 80% level.
At 3 to 4 gallons per hour, it may provide approximately 100 to 133 hours of continuous operation, or around 4 to 6 days. Intermittent use and lighter demand can extend the runtime.
What Does a Generac Generator Cost?
The purchase and installation price is separate from the cost to operate the generator.
Readers researching the brand itself can also learn who makes Generac generators and how the company’s product lines differ.
The cost of Generac generator ownership includes the equipment, installation, fuel, and recurring maintenance.
The generator unit alone may cost about $4,500 to $8,000 for many large residential models. Once labor, the transfer switch, permits, site work, and fuel connections are included, the total installed cost typically ranges from $12,000 to $20,000.
A contractor should provide separate estimates for equipment, installation, annual maintenance, and expected fuel consumption.
How Much Is a Generac Generator?
Smaller standby generator units may cost between $3,000 and $5,000 before installation. Larger whole-house models may cost $6,000 to $10,000 or more for the equipment alone.
The finished project usually costs more than the generator itself because it may require:
- A transfer switch
- Electrical labor
- Gas-line or propane work
- Permits
- A concrete or composite equipment pad
- Trenching
- Panel modifications
- Startup testing
Request an itemized estimate so you can separate the equipment price from labor, permits, fuel work, electrical work, and future maintenance.
Final Takeaway on Generac Generator Running Cost
A Generac standby generator generally costs $2 to $5 per hour on natural gas, or approximately $60 to $120 for a full day.
A propane-powered 22kW model may cost $8 to $11 per hour, placing a full day near $190 to $265 under sustained use.
Homeowners should also budget about $300 to $600 per year for maintenance and approximately $12,000 to $20,000 for a complete installation.
For a closer estimate, find the fuel consumption rating for your exact generator model, then multiply it by your local fuel rate and the expected outage length.
Grounded Electric can help homeowners evaluate generator capacity, fuel requirements, transfer-switch options, installation costs, and expected operating expenses before selecting a system.
