How Much Does an Aerobic Septic System Cost?

$0Typical ≈ $10,300$25,000

What an aerobic system costs

An aerobic treatment unit (ATU) is a tank with a built-in aerator. Pumping air into the wastewater lets oxygen-loving bacteria break down waste faster and more completely than in a septic tank. EPA’s fact sheet notes the cleaner effluent can go to a subsurface field, as from a septic tank, or in some cases be discharged at the surface where state rules allow it. Your price has two parts: the unit and the dispersal system it feeds.

Item	Source figure	In 2025 dollars	Source
Aerobic treatment unit, 500–1,500 gal/day, installed	$2,500–$9,0002002	$4,500–$16,100	US EPA
Conventional drain field it discharges to (WERF model)	$4,600–$6,900year not stated	—	Chesapeake Bay Program (EPA-led federal/state partnership)
Servicing, per year	$3502000	$650	US EPA Office of Water

EPA’s installed range covers the treatment unit only. EPA also warns that when an aerobic unit replaces a failed septic system, site conditions and extra piping can add cost. Together with the drain field, that is why complete systems in market surveys run $10,000–$20,000.

Running costs: power and service

Aerobic units have moving parts that run every day. That is the main difference in lifetime cost from a gravity septic system.

Cost	What EPA’s fact sheet says
Servicing	More frequent than a septic tank; quarterly servicing recommended; about $350 a year (2000), roughly about $650 today
Labor	12–48 hours a year for suspended-growth units; 8–12 hours a year for fixed-film units
Electricity	2.5–10 kWh a day (suspended growth) or 1–4 kWh a day (fixed film), about 365–3,650 kWh a year
Common repairs	Blower or aerator failure, pump and pipe clogging, motor failure, corroded or failed controls

EPA recommends inspecting systems with pumps, float switches or mechanical parts more often than conventional systems, generally once a year. EPA’s homeowner guide says regular lifetime maintenance should be expected for aerobic units.

20-year cost: aerobic vs. conventional

The purchase price is only part of the picture. Here is a worked example over 20 years, using only the documented figures on this page, converted to today’s dollars:

Cost over 20 years	Conventional	Aerobic
Installation	about $7,000–$14,000	about $4,500–$16,100 for the unit, plus a drain field
Pumping (6 times, about every 3 years, at EPA’s ≈ $350)	about $2,100	about $2,100
Servicing (EPA ≈ $650/year × 20)	not required	about $13,000
Electricity	none for gravity systems	7,300–73,000 kWh × your rate

Even before electricity, servicing alone adds about $13,000 over 20 years at EPA’s average. That’s why aerobic units are used where the site requires them, not as an upgrade on sites where a conventional system works.

Two kinds of aerobic units

EPA’s fact sheet describes two designs. They differ in how the bacteria are held in the tank, and that changes power use and upkeep:

	Suspended growth	Fixed film
How it works	Bacteria float freely in the aerated wastewater (activated sludge), then settle in a clarifier	Bacteria grow on a surface or media that the wastewater flows over or through
Power use (EPA)	2.5–10 kWh a day	1–4 kWh a day
Maintenance time (EPA)	12–48 hours a year	8–12 hours a year
Upkeep	More labor-intensive; semi-skilled service needed	Less labor-intensive; still needs a trained service provider

If two units are permitted for your site, ask each installer which type theirs is and what its rated power draw is. Over 20 years, a unit that uses 2 kWh a day instead of 8 saves about 44,000 kWh.

Aerobic, mound or conventional?

On a difficult site, the choice is often between an aerobic unit and a mound. Both cost far more than a conventional trench, but they spend the money differently:

	Conventional	Mound	Aerobic unit
Documented build cost, today’s dollars	about $7,000–$14,000	about $19,600	about $4,500–$16,100 for the unit, plus its field
Electricity	Usually none	Dosing pump	Aerator every day, plus pump if dosed
Routine service	Pumping and inspection	Pumping, inspection, pump checks	Quarterly servicing, pumping, inspection
Space	Large field	Large raised mound	Smaller field possible where allowed
Typical reason	Good, deep soil	Shallow soil, high water table, bedrock	Small lot, poor soil, sensitive water nearby

Your soil evaluation and the state’s rules decide which of these you’re allowed to build. When more than one is allowed, compare 20-year costs, not just the installation quote.

Questions to ask before you sign

• Is the unit certified to NSF/ANSI 40, and is that model on NSF’s current listing?
• What is its rated power draw, and does it need a dedicated circuit?
• What does the first service contract include, how long does it last, and what does renewal cost?
• How does the alarm notify me (light, buzzer, remote), and who responds?
• Does the price include the drain field, spray or drip area, electrical work and yard restoration?
• Which parts wear out first (aerator, pump, filters), and what do replacements cost?

When an aerobic system is the right choice

EPA lists aerobic units as an option for:

• homes with smaller lots
• inadequate soil for a conventional field
• a high water table
• homes close to a surface water body that is sensitive to nutrients from effluent

EPA’s fact sheet also notes that many aerobic units are installed to replace failed septic systems. Your soil evaluation and permit decide whether one is required or allowed.

Choosing and maintaining a unit

• Ask for an NSF/ANSI 40 certified model. NSF publishes the certified listings. EPA’s fact sheet notes that this certification covers units of up to 1,500 gallons a day.
• Read the maintenance terms before you buy. Who services it, how often, what is included (aerator, filters, alarm, disinfection if required), and what happens after the first contract ends.
• Keep the alarm and power on. If the aerator stops, the unit works like an overloaded septic tank and can send poorly treated effluent to the field.
• Pump the tank when the service provider recommends it. Aerobic units still collect sludge.

To compare an aerobic system with other options for your home, use the septic system cost calculator. For other alternative systems, see mound septic system cost.