usefulweb.site Break-even Explorer

Money-saving & comparison

Break-even Explorer

When does an investment pay for itself? Payback, NPV and IRR for solar, EVs, heat pumps…

Presets only fill in escalation, degradation and horizon when you leave those empty; the values are listed under assumptions.

Shown in results only; no conversion is performed.

Received at the start; reduces the net investment.

per year
%/year

Empty = preset default.

%/year

Empty = preset default.

%/year
years

Empty = preset default.

Override savings for specific years (optional)

Savings entered here replace the escalated/degraded value for that year (before maintenance).

Override savings for specific years (optional)
#YearSavings
1
2

Try an example: Rooftop solar with a grant · Insulation project, flat savings, 15 years

How it works

Enter an upfront investment, subsidies and the yearly savings it brings, with optional price escalation, performance degradation and maintenance. The explorer returns simple and discounted payback (fractional years), NPV, IRR and a year-by-year cumulative cash-flow table.

  • Net investment (year 0 outflow) = upfront investment − subsidies.
  • Savings in year t = year-1 savings × (1 + escalation)^(t−1) × (1 − degradation)^(t−1), unless overridden for that year.
  • Net cash flow in year t = savings − maintenance (maintenance is constant in nominal terms).
  • Simple payback = the year in which cumulative cash flow turns non-negative, interpolated linearly within that year (savings assumed to accrue evenly).
  • Discounted payback uses cash flows discounted by (1 + r)^t; NPV = −net investment + Σ net cash flow ÷ (1 + r)^t.
  • IRR = the rate at which NPV = 0, found by bisection between −99% and 1000% (null if NPV does not change sign in that range).
  • Presets only supply defaults for escalation, degradation and horizon when those fields are left empty; the values used are always listed.

For scripts and AI agents

  • JSON API: POST https://breakevenexplorer.usefulweb.site/api/v1/calculate (same calculation as this page)
  • Interface description: OpenAPI 3.1 · AI guide: llms.txt
  • MCP server (Streamable HTTP): https://breakevenexplorer.usefulweb.site/mcp · tool name break_even_explorer
Example request
curl -s -X POST https://breakevenexplorer.usefulweb.site/api/v1/calculate \
  -H 'content-type: application/json' \
  -d '{"preset":"solar","currency":"EUR","upfrontInvestment":12000,"subsidies":1500,"annualSavings":1100,"maintenancePerYear":100,"discountRatePercent":3}'
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