Normally, underground tanks are safer than above-ground tanks. One reason is that it’s easier for these tanks to stay temperate in extreme weather, particularly in the freezing cold. Underground tanks are also safer in the event of a leak. Underground propane tanks have a slightly longer lifespan than above ground tanks due to the fact that the ground protects the tank from harsh weather. On average, underground propane tanks last about 30-40 years. The best benefit of underground propane tanks is that they’re temperature controlled. This is because they are less exposed to extreme heat or winter cold. Extreme temperatures can impact the propane in the tank, and being underground protects the fuel from the effects of the environment. Underground propane tanks are a great way to store propane and not lose space in your yard or have to look at the tank. They are also protected from the effects of fire. But they can rust and cause problems for their owners.