Backup Generators · Service

Natural gas or propane — the fuel decision

Most residential standby generators will run on either, and they are converted at installation. The choice is not really about the machine: it is about what your site already has, what happens to that supply in the disaster you are preparing for, and who has to deliver.

Get matched free All backup generators services

In short

What is natural gas generator installation?

Most residential standby generators are built to run on either natural gas or propane, and are configured for one at installation. Natural gas comes from the street with no tank, no refills and no storage limit, so it is the default wherever a gas main is available. Propane is what you use where there is no main — it stores indefinitely, but it needs a tank, setbacks of its own, and a supplier who can still deliver during whatever event caused the outage.

Triggers

Signs you need natural gas generator installation

You have decided on a standby generator and now have to tell the installer which fuel to configure it for
There is a gas main at the property already serving a furnace or a water heater, and you want to know whether it can take a generator as well
You are rural, off the main, and choosing between a propane tank for the generator and a bigger one that also serves the house
You already have a propane tank for heating or cooking and want to know whether it is large enough to add a generator to
You live somewhere with earthquake risk, where the gas supply itself can be interrupted by the same event that takes out the power
You have been quoted for a generator and the gas work is a vague allowance rather than a priced line, and you want to know what sits behind it

Seeing something not on this list? Browse backup generators problems by symptom →

The job

How natural gas generator installation actually works

Establish what fuel the site can realistically have

Half the decision is made for you. No gas main means propane. A main at the property means natural gas is almost always the practical choice, because there is nothing to store, nothing to refill and no tank taking up a setback on your lot. The genuinely open cases are properties with a main but a supply that is already fully committed, and properties with an existing propane tank.

Watch for: A recommendation made without confirming what is actually at the meter. "You have gas" and "you have gas capacity left" are different statements, and only the second one matters here.
Do the gas load calculation on natural gas

A generator is one of the largest gas appliances a house can have. The calculation adds the generator to everything else on the system — furnace, water heater, range, fireplace, pool heater — and checks the meter and the service line against the total. Where it does not fit, the answer is a larger meter or an upgraded service, applied for from the utility.

Watch for: The calculation left until after the deposit. It is the most common reason one of these projects stalls, and the utility timeline for a meter upgrade is entirely outside your installer's control.
Size the pipe for the actual run, not the straight-line distance

Gas pipe sizing is a function of the load and the length of the run, including the fittings. A generator sited a long way from the meter needs larger pipe than one close to it, and this is a real cost that varies with the position you chose for exhaust and noise reasons.

Watch for: A pipe size worked out on a shorter route than the one that gets installed. An undersized run starves the engine under load and shows up as a machine that runs fine on test and stumbles when the air conditioning starts.
On propane: size the tank around days, not gallons

The right question is how many days of running you want before someone has to deliver. Consumption depends on the machine and how heavily it is loaded, and the manufacturer publishes consumption at half and full load — those figures plus your target duration give you a tank size. A tank shared with house heating needs both demands counted.

Watch for: A tank sized to fit the budget or the corner of the yard. A generator that empties a small tank in two days during a regional event, when every supplier is already committed, has not solved the problem you bought it for.
Site the tank to its own setbacks

Propane tanks have separation requirements from buildings, property lines and ignition sources, and those interact with the generator's own clearances. Underground tanks relax some of the visual and setback problems at a higher installed cost and with their own requirements.

Watch for: A tank position picked to be out of sight without reference to setbacks. On a tight lot the tank and the generator can end up competing for the same compliant space, and that is better discovered on paper.
Configure the machine for the fuel and check the rating you are getting

Conversion between fuels is normally a kit and an adjustment done at installation. It is not cosmetic: manufacturers publish separate output ratings for natural gas and propane, and the natural gas figure is usually the lower of the two. If your sizing was based on the propane number and you are installing on natural gas, your headroom is smaller than you think.

Watch for: Sizing quoted from one fuel's rating and the machine configured for the other. Ask which figure the load calculation used, and confirm it matches the fuel actually being installed.
Pressure test, permit and commission

New gas piping is pressure tested and inspected under a gas permit in most jurisdictions, separately from the electrical inspection. Commissioning then runs the machine under load on its real fuel supply to confirm it holds pressure and output when the big loads come on.

Watch for: A gas connection made without a permit or a test, or commissioning done unloaded. A supply problem only appears under load, which is precisely when you cannot afford to discover it.

Money

What does natural gas generator installation cost?

The gas work is usually a four-figure element of a standby generator project, driven by the length and size of the run rather than by the machine. Propane adds a tank, bought or leased. A utility meter or service upgrade is priced separately by the utility. See the generator cost guide.

See the full natural gas generator installation cost guide — by material, size and region →

Straight answer

When natural gas generator installation is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

Natural gas is wrong when your outages come with gas interruptions. In earthquake country the same event can take out both, and a gas main is not something you can stockpile. Where that is the realistic scenario, an on-site propane tank is genuinely more resilient because the fuel is already on your property.
Propane is wrong when nobody can deliver during the event. A tank is only as good as the refill, and regional storms are exactly when suppliers are overcommitted and roads are bad. If you are choosing propane, size for the outage you actually fear, not for the average one.
Neither, if the gas load calculation says your meter is full and you will not upgrade it. Running a generator on an inadequate supply is not a compromise you can quietly make — it starves under load and the machine fails when it matters. Either upgrade the service or reconsider the size of the machine.
Do not convert an existing house propane tank without counting the heating. A tank sized for a furnace and a range does not have a generator's worth of spare capacity in the middle of the winter storm that caused the outage, which is when both demands peak together.
Propane in extreme cold with a small tank is a weak arrangement. Liquid propane has to vaporise to be used, and vaporisation slows as temperature falls and as the tank empties. A small, low tank asked for high output on the coldest night of the year is the situation where this becomes a real limit. Talk to your supplier about tank size for your climate rather than assuming.
Diesel is rarely the residential answer. It is common in commercial standby because of the fuel storage and load characteristics, and at house scale it brings on-site fuel that degrades, needs polishing or turnover, and a machine that is louder. Unless you have a specific reason, this is a two-fuel decision.

Your options

Types of natural gas generator installation

Natural gas

No tank, no refills, unlimited runtime while the main holds pressure. The default where a main exists.

Dual-fuel and conversion kits

Most machines can be configured for either at installation — and reconfigured later if the site changes.

The rest of the project

Siting, pad, permits, lead times and sizing.

Compare backup generators options side by side →

Before you sign

What to check when hiring for natural gas generator installation

Can I see the gas load calculation, including the generator?

It is the go/no-go on natural gas. You want it in writing before a deposit, along with what happens and who applies if the meter needs upgrading.
Which output rating did you size from — the natural gas figure or the propane figure?

They differ, and natural gas is usually the lower one. Sizing from the wrong figure quietly removes your headroom.
What run length and pipe size are you using, and does that match the route you will actually take?

Undersized pipe on a long run produces a machine that tests fine and stumbles under real load. Get the numbers on the quote.
On propane: how many days will this tank run the generator at a realistic load?

Days is the useful unit, not gallons. Ask them to show the manufacturer's consumption figures they used to get there.
Is the tank bought or leased, and who can refill it?

Leased tanks frequently tie you to one supplier at their price. That matters over a fifteen-year ownership and it is easiest to negotiate at the start.
Who is doing the gas work, are they licensed for it, and is a gas permit being pulled?

Gas and electrical are separate trades, separate permits and often separate inspections. Find out whether one company covers both or whether you are coordinating two.
Will the commissioning test run the machine under load on the installed supply?

An unloaded test proves almost nothing about the fuel supply. A supply that is marginal only reveals itself when the large loads come on.

All backup generators hiring checklists →

Local pros

Natural Gas Generator Installation near you

Local pro matching for natural gas generator installation is rolling out by metro. Enter your ZIP and we'll match you with vetted pros in your area today.

Related work

Often done at the same time

Whole Home Generator Installation

The project the fuel decision sits inside

Generator Transfer Switch Installation

The electrical half of the install

Generator Maintenance

Fuel system checks and annual service

Generator Repair

When it starts and will not carry load

All backup generators services →

FAQ

Natural Gas Generator Installation — questions people ask

Still have a question? Talk to our team →

Is natural gas or propane better for a standby generator?

Natural gas wherever a main is available and has capacity, because there is no tank, no delivery and no runtime limit — the machine can run for as long as the outage lasts. Propane where there is no main, or where you specifically want the fuel on your own property because the same event that cuts your power might cut the gas. The decision is usually made by what your site already has rather than by preference.

Can a generator run on both natural gas and propane?

Most residential standby generators are built to run on either and are configured for one at installation, generally with a kit and an adjustment. That flexibility is real and useful — a machine can be reconfigured later if you connect to a main or move off one. What you cannot do is switch back and forth casually: it is a set-up operation on the machine, not a valve you turn.

Does a generator produce less power on natural gas than on propane?

Typically yes, slightly, and manufacturers publish separate ratings for each fuel — natural gas is usually the lower figure. It matters for one practical reason: if your sizing was worked out from the propane rating and the machine is installed on natural gas, you have less headroom than the calculation assumed. Ask which figure was used, and make sure it matches the fuel you are actually getting.

What size propane tank do I need for a generator?

Work backwards from days of runtime. The manufacturer publishes fuel consumption at half and full load; multiply by the number of days you want to survive without a delivery and you have a tank size. Then add house heating and cooking if the tank is shared, because in a winter storm both demands peak at once. Sizing to fit the yard rather than to the outage is the mistake worth avoiding.

Will my gas meter handle a generator?

It has to be calculated rather than assumed, because a generator is one of the largest gas loads a house can carry and a meter sized for a furnace, water heater and range may have nothing left. Where it does not fit, a larger meter or an upgraded service is an application to the utility with its own timeline. Get the calculation in writing before you commit money, since this is the item most likely to delay the project.

Does propane go bad in storage?

No, and that is one of its genuine advantages — unlike petrol or diesel it does not degrade in the tank, so a propane generator can sit for years and still have usable fuel. The practical limits are different: you need a tank with enough in it, a supplier who can reach you when the roads are bad, and in very cold weather enough tank surface and liquid volume for the propane to vaporise fast enough to feed the engine at load.