Honest solar math, built for homeowners
GreenCalcs exists for one reason: most "free solar quotes" are really lead-generation forms that sell your phone number to three installers. We wanted the opposite — tools that give you the real numbers, in private, before anyone tries to sell you anything.
Our methodology
Every number on this site traces back to a primary source. We deliberately avoid installer marketing material, because it tends to be optimistic. Here is exactly where our data comes from and how often we update it:
| Input | Source | Updated |
|---|---|---|
| Installed cost per watt | NREL benchmark + market reports | Quarterly |
| State incentives & SRECs | DSIRE (NC Clean Energy Tech Center) | Quarterly |
| Residential electricity rates | EIA Electric Power Monthly | Annually |
| Federal tax credit (ITC) | IRS Form 5695 guidance | On change |
| Panel degradation | NREL PV durability research | As published |
For the full detail on our data sources, default assumptions and editorial standards, see our dedicated methodology page.
How our calculators work
We believe a calculator you can't audit is just a black box. So every tool on GreenCalcs shows its full formula on the page, in plain English, along with the assumptions baked in (panel degradation, rate inflation, and so on). You can change any assumption and watch the result update. If our math and your installer's quote disagree, you'll know exactly which assumption to question.
What we will never do
- Sell your data. We don't collect it in the first place. Calculators run entirely in your browser.
- Gate results behind an email. You see your number immediately, every time.
- Pretend estimates are guarantees. Real payback depends on your roof, shading and utility. We say so on every page.
- Hide who reviewed the content. Our analyst is named, with real credentials, below.
How we make money
GreenCalcs is supported by display advertising. In the future we may add clearly-labeled affiliate links to products we'd genuinely recommend (for example, equipment or energy-monitoring tools). We do not run a lead-generation or quote-request form and we never sell your contact details. Any affiliate link will always be disclosed, and it will never change the numbers a calculator shows you. Our incentive is to be the most trustworthy solar calculator on the internet — not to push you toward a sale.