Typical range: about $25,000 to $50,000
Hawaiʻi Public Radio and the Hawaiʻi Green Infrastructure Authority both cite about $25,000 to $50,000 for a single-home conversion. Your quote can land outside that range.
What drives the price
- System type: septic with a leach field, ATU, or sewer connection
- Soil and percolation results, and groundwater depth
- Lot size, slope, and access for equipment
- Engineering, permits and inspections
- Distance to a sewer line, if you're connecting
- Restoring landscaping, driveways or hardscape afterward
Ways to lower the cost
Compare more than one licensed contractor. Ask about state financing on the financing page, and plan ahead instead of waiting for an emergency failure.
Sources: HPR, June 2026; HGIA