Solar Calculators

Every tool on this site runs the same calculation kernel, so a number you see on the sizing page will not contradict the number on the payback page. The difference between them is the question they answer and the inputs they foreground. All ten default to the 2026 rule: a homeowner-owned system receives a $0 federal residential credit.

• Solar Panel Size Calculator — Work out the system size in kW and the number of panels your annual usage, sun hours, roof direction and shading actually require. 2026 data, no signup.
• Solar Payback Period Calculator — Calculate your solar payback period, NPV and IRR with a 25-year cash flow using 2026 rules — $0 federal credit for homeowner-owned systems. State-specific defaults.
• Solar Cost Calculator — 2026 Net Cost — Build an itemized residential solar cost: array, battery, state credit, utility rebate and a $0 federal credit under the 2026 law. Enter your own quote.
• Solar Battery Calculator — See what a home battery adds to cost, self-consumption and 25-year savings under full-retail net metering versus net billing. No federal credit assumed.
• Solar Roof Space Calculator — Find out how much usable roof area a given solar array needs, and what your available roof area caps the system at. Includes setback and shading guidance.
• Solar Lease vs Buy in 2026 — Compare cash purchase, loan and lease/PPA in 2026, when the homeowner credit is $0 but a third-party owner may still claim the §48E commercial credit.
• Net Metering vs Net Billing Calculator — See what your utility's export credit is worth: compare full-retail net metering with avoided-cost net billing on the same system and the same bill.
• Solar Loan Calculator — Work out a solar loan payment, total interest and the 25-year net versus paying cash, with dealer fees and the 2026 $0 federal credit kept visible.
• Solar Carbon Savings Calculator — Convert your estimated solar production into avoided CO2, mature-tree equivalents and gasoline-car miles using the U.S. grid average emissions factor.