Solar Calculator – Estimate Solar Panels & Savings
Planning to install solar panels? Enter your monthly electricity usage, and our Solar Calculator will estimate your system size, the number of panels you’ll need, and your potential savings and payback time.
The basics
How this solar calculator works
Going solar starts with one question: how many panels do you actually need? This solar calculator answers that, plus a lot more. Simply enter your monthly electricity bill, and it estimates the ideal system size, the number of solar panels you’ll need, your battery backup time, and even how long it could take for your solar investment to pay for itself.
What goes into your result
- Your monthly electricity usage and how much of it you want to cover
- A custom peak sun hours number if you have one
- The exact panel model you’d use — from brands like Jinko, LONGi, Trina, Canadian Solar, JA Solar, REC, SunPower, and Q CELLS
- Whether you’re going with bifacial panels, which catch reflected light too
- A battery, if you want backup power during an outage
- Your electricity rate and install cost, to work out payback time
How to use it
- Enter your average monthly electricity bill in kWh.
- Type in your own sun hours if you know them.
- Choose a panel model, and turn on bifacial if that’s what you’re considering.
- Add a battery if you want backup power, and enter your electricity rate.
- Check your system size, panel count, and payback time in the results panel.
Who this is for
Frequently asked questions
Why do panel wattages vary so much, from 400W to 770W?
Higher-wattage panels are usually bigger and use newer cell technology. A 770W panel can do the job of almost two 400W panels, which means fewer panels and less roof space, though each one costs more.
Are bifacial panels worth the extra cost?
They can be, especially with a light-colored roof or ground-mounted setup that reflects extra light onto the back of the panel. The calculator adds an 8% yield boost when you turn this on, which is a reasonable average for a good site.
How accurate is the payback period estimate?
It’s a solid ballpark, not a quote. It uses your entered install cost and electricity rate, plus estimated production, and assumes simple 1:1 net metering. Your actual installer’s quote, local incentives, and utility rules can shift this number either way.
How big a battery do I need for backup power?
That depends on what you want to keep running and for how long. Enter your battery size and what share of your daily usage counts as “critical,” like fridges and lights, and the calculator estimates how many hours that battery would last.
What if I don’t know my peak sun hours?
If you’re unsure, search for “[your city] peak sun hours” or check a reliable solar resource map. Entering an accurate value helps the calculator provide more realistic estimates for system size, panel count, and energy production.
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