Not your parent poster, but the tanks are commonly installed above-ground in the rural USA. It is propane (C3H8), which is liquid under pressure. Tanks are refilled as needed depending on usage via a tanker truck. I assume this is monthly but I don't personally have one.

In the US, natural gas normally refers to methane (CH4) heating, attached to a city methane heating grid. I pay a monthly bill per cubic foot of methane burned. Currently my water heater and furnace are methane. I live near Kansas City.

As residential development continues to expand and natural gas delivery systems do not to match in many areas the use of propane has moved beyond the rural US. I have a house in a suburban neighborhood developed in the last 10 years and all the houses have buried propane tanks instead of natural gas hookups. The propane fuels heating systems, hot water heaters and stove tops. Most have grills and fire pits also attached. I have all those plus the propane fuels an emergency whole house generator.

How often tanks are refilled depends upon your particular usage pattern and the time of year. Refills can occur on demand, on an automatic basis determined by looking at your past usage patterns or as in my case triggered by an IoT connected meter which notifies my propane supplier when my tanks fall below a pre-determined level. Depending on the time of year it can be 3 months or 6 months between fills.

A township I lived in had a provision against natural gas in the master plan.

Not sure if it was an actual blocker, or just a statement that there was no plan to install infrastructure.

It depends on tank size and usage. I have small tank I use just for a range and it gets filled once a year—I use less than the minimum.

> the tank is permanent and you refill it somehow? If yes, how often?

Yup, dug into the ground when the house was built, and refilled basically once every two years ever since.

Given I used to be a lab chemist, it's oddly fascinating watching the tanker drive up and then the best part of 1000kg of propane is pumped into a tank under part of your garden...

We were told "no naked flames within 3m of the tank" - we BBQ at the other end of the garden :)

It depends on the heating need and size of the tank.

In the US, there is nothing unusual about a 1,000 gallon tank that you might fill twice a year.