Natural Gas vs Propane Standby Generator: Choosing the Fuel for a Texas Home

The natural gas vs propane standby generator decision is one most Texas homeowners do not get to make from scratch. If the street has natural gas service and the house is already connected, natural gas is usually the easy answer. If the house is outside the gas company's lines, as many homes in the Hill Country and on acreage around San Antonio are, propane is usually the only answer. Between those two cases there are real tradeoffs, and they affect the size of the unit, how long it can run, and who has to be involved in the install.

We sell and install Generac home standby and commercial generators, and the fuel comes up on every Generac generator sizing visit. This post covers what we look at and why.

Start with what is at the address

Look at what the house already has. A gas meter on the side of the house means natural gas service, and a large tank in the yard means propane. Some homes have neither, and some have natural gas available at the street but never connected. Each of those leads somewhere different.

• Natural gas already connected: the usual path is to run a line from the meter to the generator, if the meter and service can carry the added load.
• Propane already on site: the generator can often be fed from the existing tank, if the tank is large enough, or from a larger one.
• Natural gas at the street but not connected: the gas utility can tell you what a new service involves.
• No gas of either kind: propane is usually the path, with a new tank set by a propane supplier.

Natural gas: the meter is the question

Natural gas has one big advantage: it is delivered by pipe, so there is no tank to fill and the run time is not limited by what is stored in the yard. As long as the gas keeps flowing during the outage, the generator keeps running.

The question is capacity. A gas meter and service are sized for the appliances the house had when it was connected: a furnace, a water heater, a range, maybe a dryer. A standby generator can draw a lot of gas at full load, and it may run at the same time as all of those. If the meter or the service cannot supply everything at once, the generator can struggle under load. Whether the meter needs to be upgraded is a question for the gas utility, and the sizing of the line from the meter to the generator is a question for a licensed plumber.

Propane: the tank is the question

Propane is stored on site, which means the generator does not depend on a pipeline during an outage. It also means run time is limited by how much fuel is in the tank. A small tank that runs a water heater for weeks can be emptied by a generator running at load through a long outage.

Sizing the tank for the run time you want, setting it, and keeping it filled are the propane supplier's work. They will want to know which generator you are installing and how long you want it to run between fills. Some homeowners keep a larger tank for that reason, and some arrange a delivery schedule before storm season.

Output on each fuel

Many home standby units are rated for both fuels, and the rated output is often somewhat different on each. The spec sheet for the model lists its output on natural gas and on propane. Size the unit on the output for the fuel you will actually use, not on the larger of the two numbers. If you are close to the line on your load list, the fuel can be the thing that decides which size you need.

Sizing the unit to your loads is a separate step, covered in our guide to Generac generator sizing for Texas homes.

Who does what on a standby generator install

A standby generator install involves more than one trade, and it helps to know who does each part before the work starts.

• The electrical work: the transfer switch, the wiring between the generator and the panel, and the electrical permit. That is our part.
• The gas line from the meter or tank to the generator: a licensed plumber.
• The gas meter or service: the gas utility.
• The propane tank, its setting and its fills: the propane supplier.

Gas line and gas connection are not included in our electrical work. That is a licensed plumber's work and we quote it separately. We coordinate with the plumber so the line is sized for the unit you choose and the connection is ready when the electrical work is.

Other things that differ by fuel

A few smaller points come up on almost every job.

• Placement: the unit and any propane tank have clearance rules from the manufacturer and the codes that apply. The tank's location is the propane supplier's call.
• Storm season: a natural gas supply needs nothing from you before a storm. A propane tank should be filled ahead of hurricane or freeze season.
• Cost to run: fuel prices change. Compare what you pay per unit of fuel today, not what someone quoted years ago.
• Other appliances: if the house already uses propane for heat or water, the generator shares that tank, and the tank should be sized for both.

Long outages and run time

Most outages are short, and either fuel handles them easily. The difference shows in the long ones, the kind that follow an ice storm or a hurricane, when power can stay out for days. That is the case to plan for, because it is the one where a generator matters most.

On natural gas, run time is not limited by storage, so the question is only whether the gas supply keeps flowing, which it usually does through an electrical outage. On propane, run time is set by how much fuel is in the tank and how hard the generator is working. A generator carrying the whole house with the air conditioner running burns fuel much faster than one carrying a few essential circuits. If you are on propane, ask the supplier how long your tank would last with the generator you are considering at the load you expect, and size the tank, or the delivery plan, to the longest outage you want to ride out.

Questions to answer before you choose

• Is natural gas already at the house, at the street, or not available at all?
• If natural gas is connected, can the meter and service carry the generator with everything else running? Ask the gas utility.
• If propane, how large is the tank, who supplies it, and how long would it last with the generator at load?
• What is the model's rated output on the fuel you will use?
• Where can the unit and any tank go, with the clearances the manufacturer and the codes require?

With those answered, the fuel decision usually makes itself, and the rest of the project can be planned around it.

Permits and inspections

Inside San Antonio, the electrical permit for a standby generator goes through the City of San Antonio Development Services Department, and the work is inspected under the 2023 National Electrical Code the city adopted effective May 1, 2025. We pull the electrical permit and meet the inspector. The gas work carries its own permit, which the plumber pulls.

For how the electrical side of the job is done, see our Generac generator installation page and our generator installation service. To have the fuel and the size looked at together, book the Generac generator sizing visit.