STP ROI & Payback Calculator
Most STP payback claims online are generic ranges — "18-24 months," "11 months," even "3-5 years" depending on which page you read. None of them are wrong, exactly; they're just averages that may not fit your actual site. This calculator uses SUSBIO ECOTREAT's real, published equipment pricing and computes your payback from your own capacity and local water cost — not a borrowed range.
How this is calculated
Annual water savings = capacity (KLD) × 365 days × reuse rate × your water tariff. Payback period = equipment cost ÷ annual savings. This is a simplified capex-only calculation — it doesn't net out O&M costs (electricity, chemicals, maintenance) against the savings, since those vary by site and are covered in detail on our cost guide. For a full total-cost-of-ownership picture specific to your site, request a technical consultation.
Why the "generic" numbers you've seen vary so much
An 18-month payback and a 3-year payback aren't necessarily inconsistent claims — they're often describing different water tariffs, different reuse rates, or different capex assumptions without saying so. A site paying ₹15/KL for municipal water with 40% reuse will genuinely take years longer to pay back than a site paying ₹60/KL with 90% reuse. There's no single correct number — only your number, calculated from your actual inputs.
Frequently asked questions
Why does payback period vary so much between sources?
Payback depends on three site-specific variables — water tariff, reuse rate, and equipment cost — that most generic industry figures don't specify. Two sites with the same STP can have payback periods years apart depending on local water costs and how much treated water is actually reused.
Does this calculator include electricity and maintenance savings?
No — this calculates capex payback from water-cost savings alone, which is the most site-independent comparison. SUSBIO ECOTREAT's Anaerobic + MBBR process also uses up to 70% less electricity than conventional STPs, which shortens real-world payback further but depends on your current system's baseline consumption.
What water tariff should I use if I don't know my exact rate?
Check your municipal water bill for the per-kiloliter (or per-1000-liter) rate. If you're on a tanker-supplied site, use your actual tanker cost per KL instead, which is often significantly higher than municipal rates and shortens payback considerably.
What reuse rate is realistic for my property type?
Residential and hospitality properties with landscaping and flushing reuse typically achieve 70-90%. Industrial sites depend heavily on process water reuse opportunities and vary more widely. A SUSBIO technical consultation can give you a realistic estimate for your specific site.
Equipment pricing reflects SUSBIO ECOTREAT's published rates as of the pricing table on our product page, current as of publication. Confirm current pricing during consultation, as it may be updated periodically.
Conclusion
There's no universal STP payback number, and any page — including our own — that gives you one without asking about your water tariff and reuse rate is giving you an average, not an answer. This calculator exists so you can get your own number in under a minute, built on real SUSBIO ECOTREAT equipment pricing rather than an industry-wide guess. If your result looks longer than payback claims you've seen elsewhere, that's usually because those figures include electricity and maintenance savings this tool doesn't — talk to our team for the full total-cost-of-ownership picture specific to your site, capacity, and location.
