Upgrade ROI / Payback
Simple payback and 10-year NPV at user-supplied discount rate.
Example
You enter
- Incremental cost 5000
- Annual savings 800
- Discount rate (%) 4
- Years 10
You get
- Simple payback 6.25 yr
- 10-year NPV $1488.7
Details, formula, and sources
Simple payback = capital / annual_savings. NPV = Σ (savings_t / (1 + r)^t) − capital. Discount rate r is user-supplied.
Classical capital-budgeting formulas.
Formulas free in published finance / capital-budgeting texts.
Estimate. AHJ and licensed professional govern.
Field names used by the API: incremental_cost, annual_savings, discount_rate_percent, years, simple_payback_yr, npv_dollars
- Default horizon 10 years unless user suppliesengineering practice for capital upgrades