A spread is a difference in price, or value, of two similar but different underliers

An Energy Spread trade s a type of trade between two floating prices on similar but not identical energy underliers

Detail

Spread trades are usually financially settled

Different types of Energy Spread are classified by the difference in the underliers:

• Time Spread - The commodity and delivery location are the same, the delivery period is different. Also known as a Calendar Spread
• Location spread - The commodity and delivery period are the same, the delivery location is different
• Commodity spread - The delivery location and periods are the same, the commodity is different

Many commodity spreads are associated with the cost of generating electricity, so they involve electricity as one commodity, the others may be:

• Gas - usually called a Spark Spread
• Coal - usually called a Dark Spread
• Oil - usually called a Slick Spread 

Another group of commodity spreads are associated with the cost of refining, so they involve crude oil as one commodity, the others being refined products such as gasoline. These are known as crack spreads

Spread is also used to describe the difference in prices between locations, times, commodities