About this calculator
An independent, non-commercial tool — the product of one person's research, time, and thought on how to actually reason about home solar.
One of my favorite things to do as a kid was tag along on construction jobs with my dad. He was a self-taught builder and engineer, and in the 1980s there was no lack of people wanting his help with interesting projects. One morning — after stopping at the gas station for coffee and hot cocoa, then bouncing over the railroad tracks in his tiny Toyota pickup truck — he told me that this week's job was special: installing something called solar. He explained how it worked in vivid detail and my mind just wouldn't stop turning it over. That day I played under the oak trees while the team carried the panels and ran the wires, helping where I could. I was amazed that you could make your own power and hot water, and I never stopped thinking about it!
Fast forward a few decades and I finally installed my first solar system in 2020. Like so many people, the experience wasn't awesome. Actually, it was awful. I didn't know how to think about sizing, or pricing, and I didn't know how to pick a reputable installer either. I came away sad I hadn't known what to ask for and what was possible — certain I could have done better if I'd understood those things going in.
This calculator is what came out of the research I did afterward — after I realized I needed a larger system, and after major changes to the industry. It's also partly a response to the current state of incentives, or the lack of them, and the net-metering rules now being put in place. Those rules have made the case for solar less clear, or at least more complex to calculate cleanly. I wanted a tool that took the complexity head-on and made its assumptions clear — something that didn't funnel me into a sales pipeline before I understood what I was asking for, that let me tweak the inputs with the numbers I already had and then send the result to my wife to look over.
Don't let all the detail bog you down! I hope you use it to educate yourself on the many parts of the equation, to think about solar as an investment, and — if you're a solar geek like me — to have fun with the “what if” of the whole thing. Money and return aren't the whole story, and as I have time I'll keep adding to this.
A note: I coded this with the assistance of Claude AI. Having a skilled coder at my elbow is amazing, and it presents new challenges — I hope my taste, experience, and voice come through!
Trust and provenance
Every fixed assumption the model uses is listed on the How it works page, with a link to its source where one exists and a plain label where it's my own engineering estimate. The footer on every page shows the date those assumptions were last reviewed; when a baked-in figure changes, that date moves and the change is noted. Nothing here is stored on a server — every scenario travels in the link you share.
Found something broken?
Please tell me. I'd love to hear about a bug, or an edge case where the calculator doesn't behave, or simply whether it was helpful. You can reach me at [email protected] — I'd genuinely like to hear if it helped, or where it broke.
This is planning-grade analysis, not financial advice, and I'm not a licensed financial or tax adviser. Verify rates, incentives, taxes, and interconnection rules against a real quote and your own utility bill before relying on any figure here.
Open the calculator →Or start with How it works to see the model first.