Natural Gas vs. Propane Standby Generators: Cost, Runtime, and Availability

A standby generator starts on its own when the power goes out and runs your home until the grid returns. Most residential units run on natural gas or propane (also called liquid propane, or LP). The right fuel depends on what your property has, how long outages last in your area, and what you want to spend. 

This guide compares both fuels on cost, runtime, availability, performance, installation, and upkeep.

Natural Gas vs. Propane Generators: Key Differences

The main difference is fuel supply. Natural gas arrives through a utility pipeline, so you never refill anything. Propane is stored in a tank on your property, so you control your supply but must keep the tank stocked. Natural gas costs less to run. Propane delivers more power from the same engine.

Many air-cooled units can run on either fuel, and some models are dual fuel. Always check the manufacturer's rating for each fuel type.

Entity relationships in plain terms:

Natural Gas vs. Propane Generator Costs

Natural gas is usually cheaper to run per hour, while propane usually adds upfront costs for a tank and first fill. Installed whole-house systems are commonly quoted between $7,000 and $15,000 in the US, and propane setups often cost more because of the tank.

The figures below come from contractor and retailer guides, not an official price list. Prices change by region, so use them as a starting point and get written quotes.

Upfront costs (commonly quoted US ranges):

Running costs per hour: One 2026 analysis, using US average fuel prices, estimated that a 22 kW generator at half load burns about 228 cubic feet of natural gas or about 2.53 gallons of propane per hour. That works out to roughly $4.52 per hour for natural gas and $6.76 per hour for propane, or about $108 versus $162 for 24 hours. A separate contractor guide says propane typically costs 40 to 60 percent more than natural gas for equal output.

Your local gas rates and propane price will change these numbers. To estimate your own cost, multiply the hourly fuel use by your local price per unit.

Ongoing costs: Annual service is often quoted at about $200 to $600 per year. Propane owners may also pay tank rental or delivery fees.

How Runtime Differs Between Natural Gas and Propane Generators

A natural gas generator can run as long as the utility keeps supplying gas, so runtime is not limited by a tank. A propane generator runs until the tank is empty, so runtime depends on tank size, load, and how much fuel is left.

For propane, the math is simple: usable gallons divided by gallons per hour. Tanks are generally filled to 80 percent, so a 500-gallon tank holds about 400 usable gallons.

Using the 22 kW figures from the sources above:

These are calculated estimates, not guarantees. Real runtime depends on your electrical load, outdoor temperature, and the exact model. Most homes do not run a generator at full load all day, so real runtime is often longer than the full-load figure.

Natural gas has a different limit: your meter and gas line. One retailer guide notes that many residential meters deliver about 250 cubic feet per hour in total, while a 22 kW generator at full load wants around 306. Your furnace, water heater, and stove also draw from that same supply. A gas utility may need to upsize your meter or regulator.

Natural Gas vs. Propane: Fuel Availability During Power Outages

Natural gas is delivered underground and does not need refilling, which is a strong advantage in a long outage. Propane is stored on site, so you do not depend on the utility, but you do depend on your tank level and on delivery trucks if the outage runs long.

Natural gas:

• Supply is continuous while the utility network keeps gas flowing.

• You never need to schedule deliveries.

• The risk is a utility-side interruption, such as damage to lines or a regional shutdown. These events are less common than power outages, but they can happen.

Propane:

• Your fuel sits on your property, so a grid outage does not cut it off.

• Propane stores for years without breaking down.

• During storms, blocked roads and high demand can slow deliveries.

• You need to watch the tank gauge. Remote tank monitors can send alerts when the level drops.

If you choose propane, keep the tank above a safe level before storm seasons and ask your supplier about priority delivery for standby customers.

Generator Performance, Power Output, and Efficiency Compared

Propane gives slightly more power than natural gas from the same generator because propane has more energy per cubic foot. Many air-cooled units list a lower kW rating on natural gas. One example is a 22 kW unit rated at about 19.5 kW on natural gas.

That output difference is called derating. Retailer guides put it at roughly 8 to 12 percent. Check the exact rating for your model.

Fuel use also drops with load, but not in a straight line. A generator running at half load does not use exactly half the fuel. One guide says a typical unit uses about 65 to 70 percent of its full-load fuel at half load. This is why sizing matters. An oversized unit wastes fuel, and an undersized one cannot carry your load.

Most standby generators start within about 10 to 30 seconds of an outage. The automatic transfer switch then moves your home's load from the grid to the generator.

Installation Requirements for Natural Gas and Propane Standby Generators

Both fuel types need a level pad, an automatic transfer switch, an electrical connection, a permit in most areas, and licensed installers. Natural gas also needs a gas line and enough meter capacity. Propane also needs a tank, regulators, and the right setback distances.

Shared requirements:

• A concrete or composite pad rated for the unit

• Clearances from windows, doors, vents, and walls set by the manufacturer and local code

• An automatic transfer switch wired to your main panel or a subpanel

• Electrical permits and inspections

• A professional start-up and test

Natural gas specifics:

• A correctly sized gas line from the meter to the generator

• Possible meter or regulator upgrade by the gas utility

• Gas line pressure testing

• Enough gas flow for your other appliances at the same time

Propane specifics:

• A tank, either owned or leased, installed above ground or buried

• A regulator set and piping from the tank to the generator

• Setback distances from the house, property lines, and ignition sources, set by local code

• Truck access for deliveries

• A supplier contract

Rules for clearances and tank placement vary by location. Ask your installer and local building department for the exact requirements before you finalize the site.

Maintenance and Long-Term Operating Costs

Natural gas and propane generators need very similar maintenance because they use the same type of engine. The difference in long-term cost comes mostly from fuel price and propane tank fees.

Routine tasks for both:

• Weekly self-test, often 5 to 20 minutes depending on the model

• Annual professional service

• Oil and oil filter changes

• Air filter checks

• Spark plug replacement

• Battery testing and replacement

• Visual checks for leaks, rust, and pests

Fuel-specific tasks:

One contractor guide estimates that over ten years, propane fuel costs for weekly test runs and outages can run several thousand dollars higher than natural gas. Treat that as a rough estimate, since it depends on how often you lose power and on local prices.

Weekly exercise cycles do use fuel. A contractor guide estimates about $25 to $75 per year for natural gas and $50 to $150 for propane.

Advantages and Disadvantages of Natural Gas Standby Generators

Advantages:

• No fuel deliveries or tank to monitor

• Lower fuel cost per hour in most areas

• No on-site fuel storage

• Continuous supply during long outages, as long as the gas network works

• Lower upfront cost when a gas line is already in place

Disadvantages:

• Not available in every area

• Lower rated output on many models

• Depends on a working utility pipeline

• May require a meter or regulator upgrade

• Shares gas capacity with your other appliances

Advantages and Disadvantages of Propane Standby Generators

Advantages:

• Works anywhere, with no utility gas line

• Full rated output on most air-cooled models

• Fuel stores for years without going bad

• Independent of the utility gas network

• Tank size can be matched to your outage risk

Disadvantages:

• Higher fuel cost per hour

• Needs a tank, which adds upfront cost

• Needs refills and delivery planning

• Runtime is limited by tank level

• Delivery can be slow during major storms

Which Is Better for Rural Homes and Properties Without Gas Lines?

For rural homes without a natural gas line, propane is usually the better choice. It works anywhere a truck can reach, stores fuel on site, and gives full rated output. Dual-fuel models add flexibility if a gas line may arrive later.

Rural properties often face longer outages and slower repair crews. That makes tank size important.

Tips for rural propane setups:

• Choose a tank that matches your outage history. A larger tank gives more days of runtime.

• Add a remote tank monitor for level alerts.

• Set up a delivery contract with a reliable local supplier.

• Keep the tank at a safe fill level going into the storm or winter season.

• Place the tank where delivery trucks can reach it in bad weather.

• Load-management devices can help stretch runtime by shedding large loads like electric dryers or water heaters.

If a gas line runs near your property, ask the gas utility about connection cost and available meter capacity before you decide. Some rural homes are close enough to a main line for natural gas to make sense.

How to Choose the Right Standby Generator Fuel for Your Property

Choose natural gas if you already have a gas line with enough meter capacity. Choose propane if you do not have a line, want fuel independence, or need full rated output. Size the generator to your load and the fuel supply to your longest likely outage.

Use this checklist:

1. Do you have natural gas service? If yes, ask the utility if the meter can support the generator.

2. How long are your typical outages? Longer outages favor either natural gas or a large propane tank.

3. What do you need to power? List your critical loads, such as heating, cooling, well pump, and refrigeration.

4. What is your local fuel price? Compare local propane and natural gas rates.

5. What is your upfront budget? Include the tank, gas line work, and permits.

6. Can trucks reach your property? This matters for propane delivery.

7. What do local codes require? Ask your building department before you buy.

Get written quotes from at least two licensed installers and ask each to show the load calculation, fuel line plan, and permit costs.

Final thoughts

Natural gas standby generators cost less to run and never need refueling, but they depend on your utility line and lose some output. Propane generators deliver full rated power and store fuel on site, yet they need a tank and cost more per hour. If you have a gas line with enough meter capacity, natural gas is usually the simpler choice. If you live in a rural area or want independence, propane makes sense. Get written quotes, check local code, and size the fuel supply for your longest likely outage.

FAQs

Is Natural Gas Or Propane Better For A Standby Generator?

Natural gas is better if you have a gas line, because it costs less to run and needs no refills. Propane is better without a gas line or when you want on-site fuel.

Which Fuel Is Cheaper To Run, Natural Gas Or Propane?

Natural gas is usually cheaper per hour. One 2026 analysis estimated about $4.52 per hour for natural gas and $6.76 for propane on a 22 kW unit at half load. Local prices will change these numbers.

How Long Will A 500-Gallon Propane Tank Run A Generator?

A 500-gallon tank holds about 400 usable gallons. At roughly 3.6 gallons per hour for a 22 kW unit at full load, that is about 111 hours. Lighter loads last longer.

Do Natural Gas Generators Produce Less Power Than Propane?

Yes, on many models. A 22 kW unit may be rated around 19.5 kW on natural gas, because natural gas has fewer BTUs per cubic foot. Check your model's rating.

Will A Natural Gas Generator Work If The Gas Supply Is Cut?

No. It needs gas flowing to the unit. Utility gas interruptions are less common than power outages, but they can happen, so some owners choose propane or a dual-fuel model.

Does Propane Go Bad In Storage?

No. Propane does not degrade the way gasoline or diesel can, so a stored supply stays usable for years.

Can One Generator Run On Both Natural Gas And Propane?

Some can. Many air-cooled units are built for either fuel, and some are dual fuel. Switching may require a conversion kit or settings change, so follow the manufacturer's instructions.

Do I Need A Permit To Install A Standby Generator?

Most areas require electrical and fuel line permits and an inspection. Requirements vary, so ask your local building department.

How Much Extra Does A Propane Tank Add To The Cost?

One contractor guide quotes about $1,500 to $3,000 to buy a tank, or $400 to $800 per year to rent, plus the first fill. Prices vary by region and tank size.

How Often Should A Standby Generator Be Serviced?

Most manufacturers recommend annual professional service plus a weekly self-test. Follow your model's manual for oil change and part replacement intervals.