Quick answer: A larger fuel tank does not automatically mean a longer useful runtime. Compare each generator’s published hours at the same percentage of rated load, with the same fuel and operating conditions.
Read the test condition
A listing may quote runtime at 25%, 50%, or another load. Eight hours at a light load cannot be compared fairly with six hours at half load. Find the rated continuous watts, calculate your expected draw as a percentage, and look for a runtime figure near that operating point.
Estimate your working day
If your work needs 1,500 W from a 3,000 W continuous generator, your approximate load is 50%. Use the manufacturer’s runtime at 50% as a planning estimate. Motor starts, changing demand, ambient temperature, elevation, and maintenance condition can alter real consumption. Keep a reserve rather than planning to run the tank dry.
Refuel safely
Shut down and let the engine cool before refueling, following the manual. Store fuel in approved containers away from ignition sources. For backup use, account for fuel availability during a long outage and any oil-check or service interval. A quiet unit with inadequate runtime can still be the wrong choice.
Need help matching these checks to a specific model? Ask the KayrosTool team with the product name and your intended use.