Natural Gas Generators: Costs, Sizes, Fuel Use & Best Uses for Home Backup

What Is a Natural Gas Generator?

A natural gas generator converts natural gas into electricity using an internal-combustion engine connected to an alternator.

For residential backup, the most common setup is a permanently installed standby generator connected to:

1. the home's natural-gas supply
2. an automatic transfer switch
3. the home's electrical system

When utility electricity fails, the standby system detects the outage, starts the generator and transfers selected or whole-home electrical loads onto generator power.

When utility electricity returns and stabilises, the system transfers the house back and shuts the generator down.

That is fundamentally different from a portable generator that must normally be:

• moved into position
• manually connected
• manually started
• manually refuelled

For serious automatic home backup, permanent standby is the main natural-gas use case.

Are Natural Gas Generators Good for Whole-House Backup?

Yes.

Natural gas is particularly well suited to standby generators because the home already has a continuously supplied fuel source when utility gas infrastructure is available.

The main advantages are:

• automatic operation
• no onsite bulk fuel storage
• no scheduled propane delivery
• no gasoline storage
• no tank-level monitoring
• potentially long-duration operation
• relatively low current residential fuel cost in our comparisons

The disadvantages are:

• dependence on the gas utility
• possible meter/regulator upgrades
• potentially substantial gas-pipe requirements
• lower output than propane on some generators
• no stored reserve if utility gas is interrupted

It is a strong fuel.

It is not magic.

Natural Gas Generator Sizes

Residential natural-gas standby generators cover a wide capacity range.

Current model examples in Backup Generator Guide's research include systems from roughly 9 kW NG into 50+ kW residential/light-commercial territory.

Some current examples:

The important column is Natural Gas Output.

Do not size from the number in the product name.

Does a Natural Gas Generator Produce Less Power?

Often.

But not always.

Several current residential generators are rated lower on natural gas than propane.

Examples include:

Generac Next Generation 22 kW

• 21 kW NG
• 22 kW LP

Generac Next Generation 26 kW

• 24 kW NG
• 26 kW LP

Generac Next Generation 28 kW

• approximately 25 kW NG
• 28 kW LP

Kohler 20RCA

• 18 kW NG
• 20 kW LP

Kohler 26RCA

• 24 kW NG
• 26 kW LP

But that behaviour is not universal.

Cummins examples in our current research include:

Cummins RS25

• 25 kW NG
• 25 kW LP

Cummins RS36

• 36 kW NG
• 36 kW LP

Kohler also has larger examples retaining the same output on both fuels.

So never write:

"Natural gas generators always lose power."

The correct statement is:

many residential standby generators are derated on natural gas, but the amount depends on the exact model.

What Size Natural Gas Generator Do I Need?

Size from electrical load.

Not square footage.

A 4,000-square-foot home with:

• gas heating
• gas water heating
• one efficient AC system

may require less generator than a 2,500-square-foot all-electric home with:

• heat pumps
• electric water heating
• well pump
• multiple HVAC units
• pool equipment

The correct process is:

1. identify the loads that must operate during an outage
2. calculate running demand
3. account for motor starting loads
4. decide what can be load managed
5. add sensible headroom
6. compare the result with the generator's NG rating

Use our generator size calculator for the first-pass calculation.

Then have the final system confirmed for the actual installation.

Example: Why the NG Rating Changes Sizing

Suppose the calculated requirement is:

24.5 kW

You look at a generator marketed as:

26 kW

Sounds large enough.

But if the manufacturer specifies:

• 24 kW on natural gas
• 26 kW on propane

the generator may not satisfy that 24.5 kW requirement on natural gas without additional load management.

Now compare a unit providing:

25 kW NG

That potentially changes the decision.

This is why Backup Generator Guide uses fuel-specific ratings across its model pages rather than headline capacity.

Best Natural Gas Generator Brands

There is no single best brand for every house.

Our main residential shortlist includes:

• Generac
• Kohler/Rehlko
• Cummins
• Briggs & Stratton
• Champion

For most homeowners, Generac remains our default starting point because of the breadth of its residential standby ecosystem and widespread dealer familiarity.

But natural gas makes Cummins particularly interesting because models such as the RS25 and RS36 retain equal NG and LP output.

Kohler/Rehlko also has strong residential options and larger liquid-cooled equipment.

The right decision comes down to:

• calculated load
• NG output
• installed price
• transfer equipment
• local dealer quality
• service availability

See our best whole-house generators guide for the broader shortlist.

Generac Natural Gas Generators

Generac has one of the broadest residential standby ranges in the US market.

Current project research includes Next Generation and Guardian products across mainstream whole-house capacities.

One important detail is that Generac model generations should not be mixed.

For example, current/recent 22 kW Generac evidence includes:

Next Generation 22 kW

• model 7260 / G0072600
• model 7325 / G0073250 with 200A ATS
• 21 kW NG
• 22 kW LP

Guardian 22 kW

• model 7042 / G0070420
• model 7043 / G0070430
• 19.5 kW NG
• 22 kW LP

Both can be described as "22 kW Generac generators."

They do not deliver the same natural-gas output.

See our Generac 22 kW generator guide before comparing quotes.

Generac 22 kW vs 26 kW on Natural Gas

The current Next Generation comparison is:

So moving from the current Next Generation 22 kW to 26 kW buys approximately:

3 kW more natural-gas capacity

not 4 kW.

That distinction matters when deciding whether the additional equipment cost has a real job to do.

See our Generac 22 kW vs 26 kW comparison.

Cummins Natural Gas Generators

Cummins is particularly interesting for natural-gas buyers.

Current verified residential examples include:

RS25

• 25 kW NG
• 25 kW LP

RS36

• 36 kW NG
• 36 kW LP

That equal-fuel output can be valuable where a competing generator loses several kilowatts on NG.

It does not make Cummins universally better.

Dealer quality, price, warranty and exact system design still matter.

But for a natural-gas home near a sizing threshold, Cummins deserves a proper comparison.

See our Cummins generator guide and Generac vs Cummins comparison.

Kohler/Rehlko Natural Gas Generators

Current residential Kohler/Rehlko examples include:

• 10RESV - 9 kW NG
• 12RESV - 11 kW NG
• 14RCA - 12 kW NG
• 20RCA - 18 kW NG
• 26RCA - 24 kW NG
• 24RCLA - 21 kW NG
• 38RCLC - 38 kW NG
• 48RCLC - 48 kW NG
• 60RCLB - 58 kW NG

This shows two useful things.

First, NG derating appears on several mainstream residential units.

Second, some larger liquid-cooled systems retain their full output on natural gas.

See our Kohler generator guide for the broader range.

How Much Natural Gas Does a Whole-House Generator Use?

Fuel consumption depends on:

• generator
• engine
• electrical load
• operating conditions

Do not use one cubic-feet-per-hour figure for every 20 kW generator.

Current manufacturer examples from our fuel research include:

Generac 18 kW Example

Approximate natural-gas consumption:

• 164 ft³/hour at 50% load
• 235 ft³/hour at full load

Champion 201222 Example

Approximate natural-gas consumption:

• 173.4 ft³/hour at 50% load
• 270.2 ft³/hour at full load

Consumption increases as generator load rises.

That sounds obvious, but it matters for both:

• operating cost
• fuel-system design

The gas line must be designed for the generator's required maximum demand, not its pleasant half-load consumption on an average afternoon.

How Long Can a Natural Gas Generator Run?

A utility-fed natural-gas generator has no fixed tank-style runtime.

It can continue operating while:

• utility gas remains available
• gas pressure remains adequate
• the fuel system can supply the generator
• required maintenance is performed
• the generator remains mechanically functional

That makes natural gas particularly useful for prolonged outages.

But do not call it "unlimited."

Natural-gas infrastructure can fail.

Generators can fail.

And prolonged operation can trigger hour-based maintenance.

Can a Natural Gas Generator Run for a Week?

Potentially, yes.

The fuel supply is not limited to an onsite tank.

But a seven-day generator run means:

168 operating hours

That can move the machine significantly through its maintenance schedule.

For example, some generator maintenance intervals appear around:

• 100 hours
• 200 hours

depending on model and operating conditions.

So the correct question is not simply:

"Can it run for seven days?"

It is:

"Can it run for seven days while receiving the fuel and maintenance it requires?"

See our whole-house generator maintenance guide.

Does Natural Gas Still Work During a Power Outage?

Often, yes.

Natural-gas distribution infrastructure is separate from the electric distribution network, which is why utility gas can remain available when electricity fails.

But it is not guaranteed.

Natural-gas service can be interrupted by:

• infrastructure damage
• pressure problems
• deliberate utility shutdown
• local emergency conditions

So we would never claim:

"Natural gas never goes out."

Natural gas provides utility-fed resilience, not independence from utilities.

If owning a fixed amount of fuel at the property matters more, propane deserves consideration.

Do Natural Gas Generators Work During Hurricanes?

Yes, provided:

• the generator survives the event
• natural-gas service remains available
• adequate pressure remains
• maintenance requirements are met

Natural gas has a major hurricane advantage:

you are not waiting for a propane delivery truck while roads and fuel logistics may be disrupted.

But propane has the opposite resilience advantage:

the fuel is physically stored on your property before the storm.

Which one is better depends on local infrastructure and likely disaster type.

For hurricane-prone homes, investigate the historical resilience of the actual local gas network.

Can Natural Gas Be Shut Off During a Disaster?

Yes.

Utility natural gas should not be treated as physically impossible to interrupt.

Emergency shutdowns, infrastructure damage or pressure problems can occur.

That means natural gas is best understood as:

continuously supplied fuel with utility dependency

rather than:

infinite fuel.

If complete fuel independence is the objective, stored propane or another backup architecture changes the trade-off.

Does a Natural Gas Generator Need a Larger Gas Meter?

Possibly.

Having an existing gas meter does not prove it can support a whole-house generator.

A standby generator can add a very large new gas demand.

For example, a large residential generator consuming roughly:

300+ ft³/hour

at full load represents approximately another:

300,000+ BTU/hour

using the common planning approximation of roughly 1,000 BTU per cubic foot of natural gas.

That demand sits on top of other gas equipment such as:

• furnace
• water heater
• dryer
• range
• pool heater
• fireplace

The installer needs to evaluate total connected load.

Natural Gas Generator Meter Sizing

Meter adequacy depends on:

• total BTU demand
• utility pressure
• meter rating
• regulator
• generator demand
• simultaneous appliance demand

A house might have a perfectly adequate meter for:

• furnace
• water heater
• stove

and still need an upgrade once a 20+ kW standby generator is added.

Do not accept:

"You've already got gas, so it'll be fine."

as an engineering calculation.

What Size Gas Line Does a Generator Need?

There is no universal gas-pipe size for a natural-gas generator.

Sizing depends on:

• generator maximum fuel consumption
• inlet pressure
• pipe length
• pipe material
• fittings
• pressure drop
• other connected appliances
• applicable fuel-gas code

A large generator 10 feet from the meter is a different fuel-delivery problem from the same generator 150 feet away.

Use the manufacturer's maximum fuel requirement and an actual fuel-system calculation.

Not an internet chart stripped of context.

Can a Gas Line Be Too Small for a Generator?

Yes.

An undersized fuel system can contribute to:

• poor starting
• unstable operation
• loss of output
• shutdown under heavy load

The generator can appear fine during a low-load weekly exercise and then struggle when a real outage places the house on it.

That is why full-demand fuel design matters.

The installation needs to work at:

worst credible generator load

not merely at idle.

Natural Gas Pressure Requirements

Standby generators require fuel delivered within the manufacturer's specified pressure range.

More pressure is not automatically better.

Too little can starve the engine.

Incorrectly regulated supply can create other operating and safety problems.

The correct pressure belongs in:

• manufacturer specification
• installation design
• commissioning test

Fuel-pressure adjustment is not a homeowner optimisation task.

Can You Share the Existing Gas Line?

Potentially.

But "share" does not mean "tee into whatever pipe happens to be nearby."

The entire system must still supply adequate demand when multiple appliances operate.

The calculation needs to consider a plausible high-load event such as:

• generator near full load
• furnace operating
• water heater operating
• other gas appliances demanding fuel

If the existing downstream piping cannot supply that demand, the generator may need:

• a dedicated larger line
• meter/regulator upgrade
• different routing

Natural Gas Generator Installation

A complete installation normally involves:

1. electrical load assessment
2. generator sizing
3. site selection
4. fuel-system design
5. gas-line installation
6. automatic transfer switch
7. electrical integration
8. permitting
9. load management where required
10. commissioning

The gas system is only one part of the job.

See our whole-house generator installation guide for the complete process.

Is It Expensive to Add Natural Gas Just for a Generator?

It can be.

If the property does not currently have natural-gas service, the economics change materially.

Possible new costs can include:

• utility extension
• meter
• regulator
• trenching
• long piping
• permitting

At that point propane may make more sense even if its ongoing fuel price is higher.

We would not install expensive new natural-gas infrastructure solely because somebody said:

"Natural gas is cheaper."

Compare total installed ownership economics.

Natural Gas Generator vs Propane Generator

Our default fuel call is:

Choose Natural Gas When:

• adequate gas service already exists
• convenience matters
• long utility-fed runtime matters
• you want to avoid fuel storage
• NG-rated generator capacity satisfies the load

Choose Propane When:

• natural gas is unavailable
• new NG infrastructure would be expensive
• stored fuel independence matters
• propane's higher model-specific output is useful
• tank installation is practical

The complete comparison is covered in our natural gas vs propane generator guide.

Natural Gas Generator vs Home Battery

These solve different outage problems.

A natural-gas generator:

• creates electricity continuously from fuel
• can support substantial loads
• can operate for prolonged periods while gas remains available

A battery:

• stores finite kWh
• operates silently
• has no onsite combustion
• becomes much more compelling when solar can recharge it

For long high-energy outages, the natural-gas generator normally has the advantage.

For short outages, solar homes and quiet operation, batteries can be stronger.

See our generator vs home battery comparison.

Natural Gas Generator Maintenance

Natural gas does not remove engine maintenance.

A natural-gas standby generator still requires model-specific service involving items such as:

• engine oil
• oil filter
• air filter
• spark plugs
• starter battery
• valve clearance where applicable
• inspections

Long outages can bring service intervals forward quickly.

Do not assume:

"Natural gas burns clean, therefore the generator barely needs maintenance."

It is still an internal-combustion engine.

See our whole-house generator maintenance guide.

Are Natural Gas Generators More Reliable Than Propane?

We did not find credible population-level evidence proving residential standby generators are universally more reliable simply because they run on natural gas.

Fuel availability affects whether the generator can run.

Fuel-system design affects operation.

But generator reliability also depends on:

• engine
• electrical components
• installation
• battery
• maintenance
• environment
• service quality

Do not convert fuel preference into a fake reliability statistic.

Are Natural Gas Generators Quieter?

There is not enough equivalent model-matched testing to establish natural gas as universally quieter than propane.

Noise depends more usefully on:

• generator model
• enclosure
• load
• engine speed
• installation location
• measurement conditions

Compare exact manufacturer specifications where sound matters.

Can You Convert a Generator to Natural Gas?

Some standby and multi-fuel generator models are designed to operate on either natural gas or propane.

But fuel conversion is model-specific.

Do not assume any propane generator can safely be converted to natural gas with a generic kit.

Changing fuel can affect:

• regulator configuration
• fuel delivery
• rated output
• controller setup
• warranty
• certification

Follow the manufacturer's approved configuration.

Portable Natural Gas Generators

Natural gas is not limited to permanent standby generators.

Some portable tri-fuel generators can operate on:

• gasoline
• propane
• natural gas

That can be useful for homeowners who want access to utility gas without paying for a permanent standby installation.

But portable equipment is still different from standby:

• manual setup
• connection requirements
• weather protection
• transfer equipment
• storage
• starting procedure
• output

A future tri-fuel generator guide should own that specific buying intent rather than forcing it into this standby-focused page.

Who Should Buy a Natural Gas Generator?

Suburban Home Already Connected to Gas

Strong fit.

This is the easiest natural-gas case.

Verify meter and piping capacity, then compare suitable NG-rated generators.

Large Home With High Electrical Demand

Potentially strong fit, but fuel infrastructure matters.

Large generators can create substantial gas demand.

Rural Home Without Natural Gas

Usually weak fit.

Propane normally makes more sense than extending expensive utility infrastructure solely for backup power.

Hurricane-Prone Home

Strong fit where the local gas network is resilient.

Utility-fed fuel avoids onsite refill logistics, but local gas resilience still needs consideration.

Homeowner Wanting Full Fuel Independence

Weak fit.

Natural gas remains a utility service.

Stored propane better matches that particular objective.

Questions to Ask Before Buying a Natural Gas Generator

Ask the installer:

1. What is the generator's exact natural-gas output?
2. What calculated electrical load are you sizing against?
3. What is the generator's maximum natural-gas consumption?
4. Can my current meter support it?
5. Can my regulator support it?
6. What pipe size are you proposing?
7. What pressure will the generator receive under maximum demand?
8. Are other gas appliances included in the calculation?
9. Does the quote include meter/regulator work?
10. What loads are being managed?
11. Who commissions fuel pressure under load?
12. Who services the generator afterwards?

If the salesperson cannot explain the difference between:

headline kW

and:

natural-gas kW

I would be cautious about letting them size the system.