I consider propane the best fuel to store in bulk. Large tanks (1000 gallons or larger) are readily available and are easy to get filled. There are very few regulations on its residential storage. It is stored in the tank as a liquid under pressure. When the pressure is released it turns into a heavier than air gas.
The big consideration when deciding where to place your tank is the terrain. Propane gas being heavier than air will flow downhill like water in case of a leak. Place your tank downhill from your residence and other important locations if possible. I have seen it flow downhill and accumulate under a building until it reached an ignition source. The resulting explosion destroyed the building.
Heaters, stoves, refrigerators, and other appliances are readily available at reasonable prices. If you are currently on natural gas and are thinking of storing propane and converting in an emergency, contact your propane company and get the correct size orifices for propane. You will need to change the orifice in the burner of each appliance. They are different from natural gas and if you fail to change then this can be a serious hazard.
The rating plate on the appliance should be checked to determine the type of gas it is designed for. Gas appliances that are purchased through a retailer will be labeled for use with either natural gas or LP Gas. Appliances designed for use with propane will often be labeled “LP” while “NAT” indicates natural gas. Not all appliances can be converted, check with your dealer prior to purchase.
Propane can be used to power generators and vehicle motors. In my family we have had a truck that has been powered on propane for almost thirty years. Get the conversion kits beforehand, without them; this would be a very difficult conversion to make in a real emergency.
As with any fuel, there is a certain degree of danger. Be sure and keep your tanks well maintained. Keep brush and other combustible materials away from the tanks. If you have any doubts about the installation contact your local fire department for advice.
Some information on the improper storage of small propane tanks.
The picture below depicts an unsafe storage position for small propane cylinders. The picture assumes that the 20 lb. cylinder has a little over 50% propane. Even with the tank around half full, the liquid inside is above the level of the safety relief valve. The relief valve needs to be in communication with the vapor space of the cylinder in case it opens. For this reason, all consumer propane cylinders such as this should be stored in an upright position.