Tools
Free Solar PV Calculators & Sizing Tools
Interactive calculators and utilities to help you get more from your solar installation. All tools are free, with no sign-up required.
Solar PV performance is measurable. Work out what a system pays back now the federal credit has gone, how many panels fit one string once temperature is accounted for, whether paying someone to clean your array recovers more than it costs, and when it pays to discharge a battery into the grid.
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Battery Sell Hours
Find the best hours to discharge your battery into the grid based on day-ahead electricity market prices. Covers 10+ countries and seasonal profiles.
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Solar Payback 2026
Payback now the 30 percent residential credit has expired, and whether a lease or PPA beats buying outright. Seven markets.
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MPPT String Configurator
How many panels fit one string, with cold-weather Voc rise and hot-weather Vmp drop checked against real inverter limits.
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Soiling Loss & Cleaning Payback
What dirt costs you a year, by tilt and environment, and whether a paid clean recovers more electricity than it costs.
Open toolWhy we build calculators instead of charts
A static chart tells you what happened to someone else. A calculator tells you what happens to you. That gap matters in solar, because two homes on the same street can see completely different returns from the same battery. Roof pitch, shading, tariff structure, and the local wholesale market all push the numbers around. So we'd rather hand you an input box than a generic graph and a shrug.
Take battery arbitrage. The headline pitch sounds simple: charge when power is cheap, sell when it's dear. But the real spread depends on your grid's daily price shape, and that shape is wildly different in Texas than it is in Germany. Wind-heavy grids flatten overnight prices. High-PV markets crater midday rates. The Battery Sell Hours tool bakes those regional patterns in so you're not guessing.
How to read the results
Every tool here shows the gross opportunity, not your final profit. Why the distinction? Because round-trip losses, cycle wear, and export fees all skim a little off the top. A typical lithium battery loses 10 to 15 percent moving energy in and back out. Each cycle nudges your battery a step closer to its end-of-warranty capacity. We flag those costs in the explainer sections so the headline spread doesn't oversell the case.
Want the longer reasoning behind any number? Most tools link straight to the relevant guide. The battery economics, for instance, are unpacked across our solar PV guides, and you can cross-check hardware claims against our independent product reviews.
What's coming next
The soiling calculator and the MPPT string configurator were both on this roadmap and both now exist. Still to come: a panel sizing estimator that takes roof azimuth and pitch rather than assuming a south-facing ideal, and a shading loss model for arrays with a chimney or a neighbouring tree.
Each one follows the same rule. Real inputs, honest caveats, no sign-up wall, and a result that is allowed to say the thing you did not want to hear. The soiling tool tells most temperate homeowners not to pay for cleaning, and the payback tool will tell you when a lease beats buying. A calculator that only ever confirms the purchase is a sales page with arithmetic on it.