Every number a solar plan needs can be computed with a hand calculator and patience — these tools just do it faster, and each one shows its formulas so you can check the math yourself. Plan in this order: know your load, know your sun, then size hardware, then run the money.
Interactive calculators
- Solar Panel Angle Calculator — enter your latitude, get fixed and seasonal tilt angles, with the formulas explained and a table for common US cities
- Solar Payback Calculator — estimate payback period, 25-year savings, and net present value from system cost, production, electricity rate, and incentives
Step-by-step worksheets
- How to Calculate Your Solar Load — the daily watt-hour budget every other decision depends on, worked step by step with common appliance figures
- The System Planner — the full planning sequence: usage → panels → batteries → voltage → inverter → wiring → protection, in the order that avoids rework
Where the numbers go next
Once the tools have given you panel watts, battery Wh, and payback years, the budget side takes over: the solar system cost breakdown prices those numbers line by line (installed and DIY), the state cost guides localize them, and solar lease vs buy settles how to pay for it.
Load and sun-hours feed directly into system sizing; wiring decisions flow into wire size and fuse sizing; and the whole budget-first approach is framed in Rebuilding Power From Scratch.