The cost to install a septic tank system is between $3,060 and $9,810, on average. The size of the septic tank you choose, the land you’re installing it on, the type of system you choose, and local labor costs will all influence the total cost of installing a septic system. Anaerobic septic tanks (those that don’t need oxygen) typically cost between $3,000 and $8,000. Aerobic systems, which utilize oxygen to activate bacteria and are popular on smaller properties, usually cost between $10,000 and $20,000.