Solar + Efficiency Payback Plan
This is the whole project as estimators actually run it — each step feeds the next, and the right tool is embedded exactly where you need it.
Step 1: Cut the load first
Attic to R-49–60 before sizing panels. r-value estimate tool.
Step 2: True HVAC size
Right-sized equipment after insulation, not before. figure your hvac size numbers.
Step 3: Size the array
kWh ÷ 30 ÷ sun hours ÷ 0.85 = kW. figure your solar panel numbers.
Step 4: Model the payback
Net cost after 30% credit ÷ annual savings. figure your solar roi numbers.
Step 5: Harvest rain too
Roof area × rainfall × 0.623 gal. rainwater harvesting calculator.
Done? Compare approaches on the materials comparison pages, check your state's pricing, or dive into the engineer's field guide.
Reviewed: · methodology.