Heating Aboveground & Underground Oil Tanks: How Do They Differ?

Tank HeaterAboveground Oil Tanks

Aboveground tanks are the most recognizable oil storage vessels. Their exposure makes them more visible and easier to identify. They are often easier and quicker to build and install than below ground tanks. As well as providing greater access for maintenance, repairs, and operations.

Heating aboveground storage tanks comes with its own specific set of advantages and disadvantages.


With aboveground tanks you have the option to build them indoors or outdoors. If space and regional codes allow, indoor storage tanks can greatly reduce heating costs. Inclement weather has less effect, so heaters do not have to run as often or as long. 

Indoor tanks may also have more options for immersion heater types. For example, depending on the vessel contents, a skid-mounted over-the-side heater may be used to provide heating for multiple tanks. Where explosion-proof housing is required, screw plug and flanged heaters may be more appropriate.

Another advantage of aboveground storage tanks is that they are faster to heat. They are generally smaller in size allowing them to achieve target temperatures quickly and with minimal energy expenditure. This makes heating not only responsive but cost-efficient as well.


While the smaller size of aboveground storage tanks can be an advantage for heating, it can be a disadvantage for capacity. Multiple tanks may be required to handle quantities that a single underground tank could easily contain. Using multiple tanks means also having to have multiple immersion heaters, or at least using skid-mounted heaters and systems.

As well, having the tanks aboveground means that they are taking up valuable space, regardless of whether they are indoors or out. Where space is limited, they may not be the ideal option.

If storage tanks are held outdoors they may be more exposed to weather conditions. Ice, snow, and cold winds may require the heaters to run more frequently, increasing operational costs. These can be mitigated somewhat by erecting walls and roofs to protect tanks from the elements.

Underground Oil Tanks

These storage tanks are built fully or partially underground. They require careful adherence to policies and regulations, as well as costing more to build and install. However, for the right purposes, they have some definite advantages.


If space is a premium, underground storage tanks are ideal. They are out of the way and out of sight. This opens up more room for other operations. For instance, most gas stations use underground tanks for gasoline and diesel. If they didn’t, most of them wouldn’t have enough space for cars to fill up.

Another advantage of underground oil tanks is their greater capacity. They can store much greater quantities. Although heating larger tanks is slower and requires more energy than a smaller tank, they make it possible to use one heater and tank to heat quantities that would require multiple aboveground tanks. As such, they are often more cost-efficient solutions for storing and heating large volumes of oil.

In comparison to outdoor aboveground storage tanks, underground tanks are less exposed. As such cold temperatures and inclement weather may have less effect. This can reduce risks of damage to the equipment, as well as requiring less frequent heating during winter months.


Underground storage tanks must adhere to more stringent regulations than aboveground. What materials can be stored, as well as the specific materials and types of containers are more controlled and limited. These policies help to reduce risks to property and the environment.

The design requirements for underground storage vessels can make them more expensive to build. There are greater contamination risks underground if the storage tank fails. As such, they may require secondary containers as well as spill, leak, and/or corrosion protection.

Being underground also means that these oil tanks are less accessible. This leaves less room for operations, as well as limited access for maintenance, repairs, and replacements.

Storage Tank Heaters

Wattco custom-manufactures industrial storage tank heaters for all industries and vessel types. Whether an aboveground or underground oil tank is right for your process, we can help you select the right heater and configuration for your specific application.

Contact Wattco today for tank heater quotes and information.