Quick Answer
Natural gas generators have lower fuel costs (40-50% cheaper) but require gas line infrastructure. Propane systems cost $2,000-$5,000 more upfront for tank installation but offer independence from gas grid disruptions. Over 10 years, natural gas typically saves $3,000-$8,000 in fuel costs for average outage patterns.
Why Fuel Choice Matters
Your fuel selection affects:
- Upfront installation costs (tank vs gas line)
- Ongoing fuel expenses (rate differences)
- Reliability during disasters (grid dependence)
- Maintenance requirements (fuel stability)
- Environmental considerations (emissions, fuel source)
Initial Installation Cost Comparison
Natural Gas Installation Costs
| Component | Cost Range | Notes |
|---|---|---|
| Gas line extension (if needed) | $500-$2,500 | Distance from meter to generator |
| Gas meter upgrade | $0-$800 | Required for larger generators |
| Pressure regulator | $200-$500 | If not already present |
| Permit and inspection | $100-$350 | Gas/mechanical permit |
| Total additional cost | $800-$4,150 | If gas available at property |
Propane Installation Costs
| Component | Cost Range | Notes |
|---|---|---|
| Above-ground tank (250 gal) | $1,500-$2,500 | Includes installation |
| Above-ground tank (500 gal) | $2,000-$3,500 | Recommended for whole-home |
| Underground tank (500 gal) | $3,500-$5,500 | Includes excavation |
| Tank pad/foundation | $150-$400 | Concrete or gravel |
| Gas line to generator | $300-$800 | From tank to unit |
| Initial fuel fill | $400-$800 | At $2.50-$4.00/gallon |
| Total additional cost | $2,350-$6,000 | Tank + fuel line + fill |
Net Installation Difference
| Scenario | NG Additional | Propane Additional | Propane Premium | |----------|---------------|--------------------|-----------------| | | NG available, line extension needed | $800-$2,500 | — | — | | NG not available, tank required | — | $2,350-$6,000 | $2,000-$5,500 |
Fuel Cost Comparison
Per-Hour Operating Costs (20kW at 50% load)
| Fuel Type | Consumption | Rate | Hourly Cost |
|---|---|---|---|
| Natural gas | 1.8 therms/hr | $1.50/therm avg | $2.70/hr |
| Propane | 1.8 gal/hr | $3.00/gal avg | $5.40/hr |
Natural gas is approximately 50% cheaper per hour of operation
Annual Fuel Cost Scenarios
| Usage Pattern | Hours/Year | NG Cost | Propane Cost | NG Savings |
|---|---|---|---|---|
| Exercise only | 52 | $140 | $280 | $140 |
| Typical (2-3 outages) | 150 | $405 | $810 | $405 |
| High outage area | 300 | $810 | $1,620 | $810 |
| Extended outage year | 500 | $1,350 | $2,700 | $1,350 |
10-Year Fuel Cost Projection
Assuming 3% annual fuel price increase:
| Usage Pattern | NG 10-Year | Propane 10-Year | NG Savings |
|---|---|---|---|
| Typical usage | $4,600 | $9,200 | $4,600 |
| High outage area | $9,200 | $18,400 | $9,200 |
Total Cost of Ownership Comparison
10-Year TCO: 20kW Generator
Natural Gas Scenario:
| Cost Category | Amount |
|---|---|
| Installation (w/ gas line) | $12,000-$16,000 |
| Fuel (typical usage) | $4,600 |
| Maintenance | $3,500 |
| 10-Year Total | $20,100-$24,100 |
Propane Scenario:
| Cost Category | Amount |
|---|---|
| Installation (w/ tank) | $14,500-$19,000 |
| Fuel (typical usage) | $9,200 |
| Maintenance | $3,500 |
| 10-Year Total | $27,200-$31,700 |
Natural gas saves $7,000-$7,600 over 10 years in typical usage scenarios.
Reliability Considerations
Natural Gas Advantages
- Unlimited supply: Continuous delivery during outages
- No storage concerns: No tank to monitor or fill
- Lower maintenance: No fuel degradation issues
- Consistent pressure: Utility-maintained system
Natural Gas Risks
- Grid dependence: Gas outages during major disasters (rare but possible)
- Pipeline vulnerabilities: Earthquakes, construction damage
- Pressure drops: During high-demand periods (extreme cold)
Propane Advantages
- Independence: Own your fuel supply
- Works during gas outages: Completely self-contained
- Portable: Can be used for other purposes (grills, heaters)
- No utility coordination: Simpler installation in some areas
Propane Considerations
- Tank monitoring: Must track fuel level
- Delivery scheduling: Arrange refills before storms
- Fuel degradation: Minimal but possible over years
- Tank maintenance: Inspection and recertification required
Fuel Availability by Region
Natural Gas Availability
| Area Type | NG Availability | Recommendation |
|---|---|---|
| Urban/suburban | 90%+ | Natural gas typically preferred |
| Exurban | 60-80% | Check utility availability |
| Rural | 10-30% | Propane usually required |
Regional Fuel Cost Variations
| Region | NG Cost vs National | Propane Cost vs National |
|---|---|---|
| Northeast | +20-40% | +15-25% |
| Southeast | -5-15% | -10-20% |
| Midwest | -10-20% | -5-15% |
| West Coast | +10-20% | +5-15% |
| Texas | -15-25% | -10-20% |
Environmental Considerations
Emissions Comparison
| Factor | Natural Gas | Propane |
|---|---|---|
| CO2 per kWh | 0.91 lbs | 1.32 lbs |
| Clean burning | Very clean | Clean |
| Fuel source | Fossil fuel | Byproduct of NG/refining |
Fuel Stability
| Factor | Natural Gas | Propane |
|---|---|---|
| Shelf life | N/A (delivered) | Indefinite (in sealed tank) |
| Degradation | None | Minimal |
| Storage concerns | None | Tank maintenance |
Decision Framework
Choose Natural Gas When:
- Gas service is available at your property
- You want lowest long-term fuel costs
- Extended outages are infrequent
- You prefer maintenance-free fuel supply
- Local gas utility is reliable
Choose Propane When:
- Natural gas is not available
- You want independence from gas grid
- You experience frequent gas outages
- You may use fuel for other purposes
- You’re in a remote/rural location
Consider Dual-Fuel When:
- You want backup fuel option
- Gas reliability is uncertain
- You want flexibility for price fluctuations
- Available on select generator models
Related Guides
For comprehensive fuel and cost planning:
- Generator Fuel Consumption Cost Calculator
- Home Standby Generator Installation Cost Calculator
- Whole House Generator Payback Calculator
- Generator Maintenance Annual Cost Estimator
FAQ
Is natural gas always cheaper than propane?
In most markets, yes—typically 40-50% cheaper per equivalent energy output. However, local utility rates vary significantly. Check your specific gas and propane rates before deciding.
Can I convert my generator from propane to natural gas later?
Many generators are convertible, but not all. Check manufacturer specifications. Conversion typically costs $200-$500 for parts plus labor.
How big a propane tank do I need?
For standby generators: 250 gallons (3-5 days typical runtime) or 500 gallons (7-14 days) depending on your outage expectations and generator size.
Does propane go bad?
Propane doesn’t degrade like gasoline, but tanks should be inspected and recertified every 10-12 years. Keep tank at least 30% full to minimize moisture issues.
What if the gas grid fails during an emergency?
Gas outages are rare (gas lines are buried and pressurized) but can occur during earthquakes, major floods, or infrastructure failures. Propane offers complete independence but requires tank management.
Can I bury my propane tank?
Yes, underground tanks cost $1,500-$2,500 more than above-ground but are hidden from view. Required in some HOAs. Factor in excavation costs and tank accessibility for fills.
Next Step
Use the Home Standby Generator Cost & Outage Payback Simulator to compare natural gas versus propane costs based on your local fuel rates, expected outage patterns, and installation requirements. Verify natural gas availability with your local utility before finalizing your decision.