About Solar Calculations
Going solar comes down to four numbers: how big a system you need, what it costs, how it's angled, and how you pay for it. These calculators give you each one instantly, so you walk into installer conversations already knowing the ballpark instead of taking the first quote at face value.
System size starts with your electricity use. Take your monthly kilowatt-hours, divide by your local peak sun hours and a real-world efficiency factor, and you get the kilowatts of panels you need. Divide by panel wattage and you have a panel count. Most homes land somewhere between 6 and 12 kW, or roughly 15 to 30 panels.
Cost is usually quoted per watt. Quality residential systems run about $2.50 to $3.50 a watt installed before incentives, and the federal tax credit currently knocks 30% off. Payback is simply your net cost divided by your annual electricity savings, and for most homes it lands somewhere in the high single digits to low teens of years.
Angle matters more than people expect. A panel tilted near your latitude and facing true south in the northern hemisphere captures the most energy over a year. You can tilt steeper to favor winter or flatter to favor summer. Get oriented here, then have an installer run a site-specific proposal that accounts for your roof, shading, and utility's net-metering rules. These numbers are planning estimates, not a binding quote.