How to use this calculator
- Enter System cost in $.
- Enter Tax credit in %.
- Enter Monthly bill offset in $.
- Enter Utility inflation in %.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
Net cost = gross − 30% federal credit. Payback = net cost ÷ annual savings. At $3/W installed and $0.16/kWh offset, typical US systems pay back in 7–11 years against a 25+ year panel life. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Where this fits in the project
Efficiency upgrades interact: better insulation and correct R-values shrink the heating and cooling load, which shrinks the solar array needed to offset it. Size loads first, generation second.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the solar roi calculator:
- Solar Panel Calculator — Calculate ROI from solar system size and cost.
- Electrical Load Calculator — ROI depends on how much electricity is offset.
- Cost Per Square Foot Calculator — Solar ROI vs other home improvement investments.
Frequently asked questions
Is the 30% solar tax credit still active?
The residential clean energy credit runs at 30% through 2032 under current law — confirm current-year status before contracting.
Does solar add home value?
Studies (Zillow, LBNL) find owned systems add roughly 4% — leased systems can complicate sales instead.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.