Generator Fuel Tank Capacity: Runtime vs Refueling

What tank capacity means on a listing

On a portable generator listing, tank capacity is the volume of fuel the tank holds when full. For a gasoline, dual fuel or tri fuel generator, the figure is usually stated in gallons and appears with the model name, the wattage group, the start method and the fuel type. A higher number means the tank holds more fuel before you fill it again.

Tank capacity is a capacity figure, not a runtime figure. How long a generator runs on a full tank depends on how much power the connected devices draw and on the engine's rate of fuel use. The listings on this site state the tank size, the fuel type and the wattage group; they do not state runtime hours or fuel use per hour.

Runtime and refueling: what a tank figure will not tell you

The two questions that come up together are how long a generator runs on a full tank and how often it needs a refill. A listing answers the refill question in part with the tank figure, but runtime has to be read from a separate statement. When a maker states a runtime, it is stated at a particular load, and that load condition is part of the claim.

For shopping, a larger tank generally means fewer refueling stops in the same situation, because the generator holds more fuel between fill-ups. A larger tank also adds weight when full, which matters on a unit you carry. Read the runtime figure, if the maker states one, on the maker's page and in the owner's manual.

Match the tank to your situation

In storm season, an outage can last hours, and each refueling trip means going outside to a running generator. A larger tank reduces the number of trips. Start with the best generator guide and compare the larger wattage groups in the best 5001 to 9000 watt generator guide.

For a camping trip, a small inverter set is often run for a few hours for lights or a small appliance. A tank that covers that time keeps the trip simple. For a travel trailer, the rig's connection and the run time you plan are part of the choice. See the best camping generators guide and the best generator for RV guide.

For a job site or a tailgate, the generator may run several hours at a stretch. Refueling convenience depends on whether a fuel source is close by. Compare portable sets in the best portable generator guide and the best dual fuel portable generator guide.

Fuel type and tank size together

On a dual fuel or tri fuel listing, the tank figure usually applies to the gasoline side of the generator. Propane runs from a separate tank, and natural gas runs from a utility line, so the refueling question is different for those fuels. The EIA pages on gasoline, hydrocarbon gas liquids and natural gas describe the fuels; the listing states the fuel types and the tank size.

If you are comparing a single fuel gasoline generator with a dual fuel or tri fuel unit, compare the tank figure on the gasoline side and keep the fuel question separate. The fuel types comparison article and the dual fuel vs tri fuel article explain the fuel words on a listing.

Fuel gauge and hour meter as listing words

A fuel gauge is a listing feature that shows the level of fuel in the tank, usually on the control panel. An hour meter is a listing feature that tracks how many hours the engine has run. Both appear as separate items on a listing; the tank capacity figure is the one that states how much fuel the tank holds.

An hour meter is useful for following the maintenance schedule in the owner's manual, and a fuel gauge tells you at a glance when a fill-up is close. The fuel gauge article and the hour meter article explain both terms.

Compare listings on stated tank figures

To compare two generators, read the tank figure as it is stated on each listing and compare within the same type and wattage group. A small inverter set and an open frame set in the same wattage group can have very different tanks. The best 3000 to 5000 watt generator guide is a good place to see that range.

The guides on this site compare generators on stated details: type, fuel, wattage group, electric start, RV ready, CO sensor and brand. Tank capacity is one of the stated details you can read for yourself on a listing.

Before you buy: read the safety sources

The CPSC and the CDC publish guides for portable generator use that cover where a running generator belongs and how carbon monoxide can build up indoors. Those pages are useful to read before you plan refueling stops during an outage, and they sit alongside the maker's manual as the documents that describe generator use.

The generator's owner's manual is the place to read the tank fill procedure, the fuel the maker specifies and the maintenance schedule. The listing states what is being sold; the manual states how the unit is meant to be used.

What to pick for your situation

Questions

Does a bigger tank always mean a longer run?

No. Tank capacity is how much fuel the tank holds. Runtime also depends on the load and the engine's fuel use rate. A bigger tank can mean fewer refueling stops, but the runtime figure, if the maker states one, is the number to read for hours.

Where is the runtime figure stated?

On a listing on this site, the tank size, fuel type and wattage group are stated. Runtime hours, when a maker provides them, appear on the maker's page and in the owner's manual, stated at a particular load.

Does the tank figure on a dual fuel listing apply to both fuels?

The stated tank figure usually applies to the gasoline side. Propane runs from a separate tank, and natural gas runs from a utility line, so those fuels have their own refueling questions.

What is a fuel gauge on a generator listing?

A fuel gauge is a feature that shows the level of fuel in the tank. It is listed as a separate feature from the tank capacity figure.

Should I compare tank size between an inverter and an open frame generator?

Compare within the same type and wattage group. An inverter set and an open frame set in the same wattage group can have different tanks and different weights, and they are built for different use situations.