Investing in a whole-house generator gives you peace of mind during power outages—but choosing the right fuel source is just as important as choosing the generator itself. If you’re shopping for an emergency backup power solution, you’re likely asking: What fuel source is best for a whole-house generator—natural gas or propane?
The short answer: Both fuel types have their advantages. Natural gas offers continuous fuel supply and lower operating costs, while propane provides higher energy efficiency and can be stored independently of utility infrastructure. The best choice depends on your home’s location, fuel access, and emergency preparedness needs.
In this guide, we’ll compare propane vs. natural gas for standby generators and help you choose the best fuel source to keep your entire home running during blackouts, storms, and other power emergencies.
How Whole-House Generators Use Fuel
Whole-house generators are permanently installed systems that connect to your home’s electrical panel and activate automatically during an outage. They require a steady fuel source to power an internal combustion engine, which in turn generates electricity for your home.
The two most common fuels for standby generators are:
- 🛢️ Natural Gas: Delivered via underground utility pipelines
- 🔥 Propane (Liquid Propane or LP): Stored in on-site tanks, typically 100–500 gallons
Unlike portable generators that use gasoline or diesel, whole-house units rely on cleaner-burning, long-lasting fuels for extended runtime and reliability.
Fuel Comparison Table: Natural Gas vs. Propane
| Feature | Natural Gas | Propane (LP) |
|---|---|---|
| Fuel Delivery | Utility pipeline (on-demand) | On-site tank storage |
| Storage Requirement | No storage required | 100–500+ gallon tanks |
| Energy Efficiency (BTUs) | 1,030 BTUs/cu ft | 2,516 BTUs/cu ft (more efficient) |
| Fuel Availability During Disasters | May be disrupted if lines are damaged | Available if tank is full |
| Installation Cost | Lower if gas line exists | Higher due to tank setup |
| Operational Cost | Typically cheaper long-term | More expensive per gallon |
| Environmental Impact | Slightly lower CO₂ emissions | Cleaner burning, no lead or sulfur |
| Cold Weather Performance | Consistent | Tank pressure may drop in extreme cold |
| Backup Duration | Unlimited (as long as utility is working) | Limited to tank size and refill access |
Benefits of Using Natural Gas
1. 🔁 Continuous Supply
Because it connects directly to your utility’s pipeline, natural gas provides a virtually unlimited fuel source. You won’t need to refuel, check tank levels, or schedule propane deliveries.
2. 💰 Lower Long-Term Costs
Natural gas is typically cheaper per BTU than propane, especially in areas where pipeline infrastructure is well-established. Over the lifespan of your generator, you may save hundreds (or thousands) in fuel costs.
3. 🚫 No Storage or Tank Maintenance
With no need for an external fuel tank, you eliminate maintenance, refilling, and space concerns—making installation cleaner and easier if your home already has gas service.
4. 👍 Ideal for Urban and Suburban Homes
Most city and suburban neighborhoods already have access to natural gas lines, making it the most convenient option for many homeowners.
Downsides of Natural Gas
- ⚠️ Vulnerable to service disruptions during earthquakes, floods, or major storms
- 🚫 Not available in rural areas or remote locations
- 🧰 May require costly hookup if no existing gas line is present
Benefits of Using Propane
1. 🧯 On-Site Fuel Storage = Independence
With propane, you control your own fuel supply. A full tank can power your generator for several days or weeks—without relying on external utilities.
2. 🔥 Higher Energy Output
Propane delivers more BTUs per cubic foot than natural gas, meaning it’s more energy-dense and can run your generator more efficiently under load.
3. 🌎 Cleaner Combustion
Propane burns cleanly with fewer carbon deposits. It doesn’t degrade over time and produces minimal air pollutants compared to gasoline or diesel.
4. 🏡 Ideal for Off-Grid or Rural Homes
In areas where natural gas lines don’t reach, propane is the most reliable alternative. It’s commonly used for heating, cooking, and powering backup systems in rural locations.
Drawbacks of Propane
- 💵 Higher fuel cost per hour of operation
- 🛢️ Requires large on-site tank (may be unsightly or space-restrictive)
- ❄️ Performance may decrease in extreme cold (tank pressure drop)
- 📅 Requires regular refills and fuel level monitoring
Fuel Usage: How Long Will It Last?
Propane Runtime Estimates (500-gallon tank):
- 20kW generator: ~6–8 days of continuous runtime at 50% load
- 24kW generator: ~5–6 days at 50% load
Natural Gas Runtime:
- Continuous as long as the gas utility is operational
⚠️ Note: During major disasters (like earthquakes or gas line breaks), natural gas service may be interrupted. Propane offers greater self-sufficiency in such cases—assuming your tank is full.
Which Fuel Is Better for Your Home?
✅ Choose Natural Gas if you:
- Live in an urban/suburban area with reliable utility access
- Already use natural gas for heating, water, or cooking
- Want low-maintenance, continuous fuel with no refills
- Prefer lower long-term operating costs
✅ Choose Propane if you:
- Live in a rural or off-grid area without natural gas access
- Want energy independence with on-site storage
- Need high-efficiency performance or cleaner fuel
- Are prepared to maintain and refill fuel tanks
🏠 Tip: Some dual-fuel generators offer both propane and natural gas compatibility, giving you flexibility during emergencies.
Best Generators for Natural Gas or Propane
🛡️ Generac Guardian 24kW Standby Generator
- Dual-fuel: natural gas or propane
- Wi-Fi-enabled monitoring and self-testing
- Powerful enough for whole-house coverage
🔥 Kohler 20RESCL 20kW Generator
- Factory-equipped for LP or NG
- Corrosion-resistant aluminum enclosure
- Fast 10-second response time
💨 Champion 14kW Home Standby Generator
- Affordable whole-home coverage with smart ATS
- Clean, quiet, and reliable operation
- Best for medium-sized homes
FAQs: Natural Gas vs. Propane for Standby Generators
Q: Is propane or natural gas more efficient for generators?
Propane is more energy-dense, offering more BTUs per unit—but natural gas is usually cheaper and continuously supplied.
Q: Will my generator work if natural gas service is interrupted?
No. If gas lines are damaged or shut off, the generator will not operate unless you have a dual-fuel model with propane backup.
Q: How long does a 500-gallon propane tank last during a power outage?
For a 20kW generator, a 500-gallon tank lasts roughly 6–8 days of continuous use at half load. Actual runtime varies by conditions.
Q: Can I install both propane and natural gas options?
Yes. Many standby generators are dual-fuel capable. You can choose your preferred fuel at installation or switch later with minor adjustments.
Q: Which is better for cold climates?
Natural gas is more consistent in freezing temperatures. Propane tanks can lose pressure in extreme cold unless properly insulated or buried.
Conclusion: Choose the Fuel Source That Matches Your Needs
When it comes to powering your whole house during an emergency, both natural gas and propane are excellent fuel sources. Natural gas offers unlimited supply and lower costs, while propane delivers independence, efficiency, and reliability—even when utility services are down.
By understanding your home’s location, fuel access, and power demands, you can confidently choose the fuel that best supports your backup power plan—and ensure your family stays safe and comfortable during any outage.
Need Help Choosing the Right Generator?
Start here: What Size Standby Generator Do I Need for My Entire Home? — our in-depth guide to sizing, fuel options, and choosing the perfect standby system for whole-home protection.