Wed. Oct 20th, 2021

A twenty-pound propane tank will cost you around seventeen dollars on average, with some wiggle room in either direction. While propane mileage is generally good, it varies depending on the generator and how it is used. How long would a twenty-pound propane tank last in average conditions?

Twenty pounds of propane, or approximately 4.6 gallons, should last for at least 24 hours. It’s not a straight line, but each gallon should provide at least five hours of consistent power. The generator’s ability to stretch this limited supply is determined by the load it is operating at, the amount of time it is running, and proper maintenance measures.

Not all generators are the same in terms of efficiency and running them less than optimally can result in potential damage and costly repairs down the road. Generator load issues, as shown below, are one of the most common issues that stifle generator effectiveness.

Generator Load

Generators of all types are rated to provide a specific level of power for optimal performance. A deviation from this balance in either direction can jeopardize your unit’s shelf life, among other risks.

Most generators have a minimum load range that they can handle, with the numbers typically falling between 50% and 75%. Going below this can cause a problem known as wet stacking, in which unburned fuel enters the exhaust systems and wreaks havoc on vital components.

This is a concern because running generators at less than their minimum load causes them to operate at insufficient temperatures to convert all of the fuel used cleanly. This problem can worsen over time, causing serious damage to your generator’s engine. When combined with fuel vapors, soot can accumulate and thicken into a tar-like substance. Soot deposits, in addition to premature wear and tear, reduce efficiency.

While running your generator at a lower load may appear to be a sneaky way to extend fuel life, all you’ll accomplish is introduce unconsumed fuel into the exhaust pipes. This can be handled quickly by identifying it as soon as possible – quick signs include carbon deposits, trickling tar the consistency of engine oil running down your unit, or simply unhealthy black smoke emanating.

Wet stacking can be dealt with by running your generator at the appropriate temperature to at least a 75 percent load, and it can be avoided entirely by staying at that point.

Overloading your generator can result in intermittent power fluctuations because the exceeded wattage cannot be accommodated consistently by the generator unit. It also contributes to soot buildup, which impairs functionality due to clogging. Power spikes are hazardous to any connected electronics, causing circuit boards to fail and posing a fire or explosive risk.

Power skips and premature wear on your generator are caused by both generator issues. Running your generator at the load specified by manufacturers – or at least the minimum load they’ve cleared for safe use – is the best way to get the most mileage out of those twenty pounds of propane.

Keeping it Plugged and Running vs Intermittent Use

In general, running your generator – propane or otherwise – consecutively is the best way to go. Using them for short periods of time on an as-needed basis may be more convenient, but in terms of raw cost-effectiveness, keeping it running gets you much more mileage.

This is due to the wattage difference. In particular, the difference between running and starting watts. Running watts are the amount of power required to keep your device, in this case, the generator, running. The costs to maintain the current momentum are also included in the minimal value.

Starting watts are the watts required to move your generator from its stationary state.

Keeping your generator running continuously reduces the number of times you have to pay for the startup watts.

Long-term use will not be a problem. Unless otherwise specified, most generators can last for about three weeks of continuous use – just over 500 hours of dedicated performance. But don’t push it any further. Living off the grid can make repairs difficult to complete.

Scheduled Maintenance

While propane is the longest-lasting fuel source, their engines cannot match it. Propane-powered generators have a shorter functional lifespan than their modern fuels and require strict maintenance to operate at peak performance.

Most propane-powered appliances will come with maintenance instructions or hotlines to contact the companies in charge. This may be sufficient in most cases, but if the options are inconvenient or simply unavailable, it is better to be safe than sorry.


Generators rely on a precise fluid balance to function properly. Oil should ideally be changed every hundred hours. You might also consider paying for a Fluid Analysis – the process is effective and non-invasive, so you won’t have to disassemble your generator to check.

Check for any leaks as usual. Because of the volatility of propane, fuel leaks will be extremely dangerous, and generator oil will be a net loss over time. Locate any leaks that may pose a risk in your unit as soon as possible, and check for general maintenance once a week.

Leaks are frequently caused by loose nuts or weakened rubber seals and must be addressed accordingly. To be sure, tighten any loose nuts and treat the seal with soap and water or dedicated, purpose-made products.


Generator batteries should be replaced every two to three years, but checking for some of the more common problems is simple. On a broad level, ensure that all of your batteries are in good, equal condition – a single battery with irregular voltage or corrosion marks on the poles could potentially harm the generator and any other attached equipment.

Check that the voltage of your batteries is the same across the board. Aside from outputs, cell charge time is also important to monitor. Undercharging cells reduce battery life and total capacity, whereas overcharging cells corrode the grids on positive plates, reducing overall performance.

How Long Will A Generator Run On 20lb of Propane Bottom Line

While twenty pounds of propane should last you a while, the engine’s performance is just as important as the fuel itself. To get the most out of your propane, make sure your generator is up to the task, that you’re running it according to the manufacturer’s instructions, and that you’re using it correctly.

By Beth

I'm Beth Nunes, the proprietor of preparing in the city. My family is the most important thing in the world to me. I couldn't bear the thought of my three small children going hungry, so I became obsessed with finding simple and practical ways to be prepared for the future by building food storage and gathering other emergency preparedness items.

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