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VoltCalcs

Solar Calculators

15 free solar calculators: daily load, panel size and output, battery bank size, charge time from panels, payback and savings, and tilt angle by latitude and season.

Size in this order: daily load, then panels, then the battery bank. Panels and the bank are both sized from the daily energy figure the first step gives you. For tilt, the Solar Panel Angle Calculator gives the angle by latitude and season.

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System sizing

Solar Panel and Battery Sizing Calculator

Size off-grid solar panels and a battery bank from daily usage, sun hours, losses, chemistry, depth of discharge, autonomy and inverter efficiency.

How Many Solar Panels Do I Need?

Find how many solar panels your home needs from your monthly electricity bill. Get the panel count, system size in kW, and how much of the bill it offsets.

Solar Battery Bank Size Calculator

Calculate the battery bank your off-grid solar system needs. Enter daily usage, autonomy days, chemistry, voltage, depth of discharge and inverter efficiency.

Solar Panel Roof Area Calculator

Calculate how many solar panels fit on your roof and the total output potential. Enter roof dimensions and panel specs.

How Many Batteries for a Solar System?

Figure out how many batteries your solar system needs for reliable off-grid power. Enter daily usage, autonomy, and battery specs.

Solar Panel Calculator

Free solar panel calculator: enter your daily energy use and sun hours to get the panel wattage and number of panels for a home, RV, or off-grid setup.

What Size Inverter for a 1500W Heater?

Size an inverter, battery bank, and solar array to run a 1500W space heater off-grid. Complete system sizing in one tool.

How Many Batteries for a Camper?

Calculate how many batteries your camper or van needs from one daily watt-hour total, the days you go without charging and the size of one battery.

Off-Grid Load Calculator

Calculate your total daily energy needs for off-grid living. Get recommended battery bank size and solar panel wattage for your system.

Output and charging

Solar Panel Output Calculator

Calculate daily and monthly energy output from your solar panels. Enter wattage, sun hours, and panel count for instant results.

Solar Battery Charge Time Calculator

Calculate how long your solar panels take to charge your battery bank. Accounts for sun hours, system voltage, battery chemistry, charge efficiency and losses.

Solar Watts to Amps Calculator

Convert solar panel output from watts to amps at any system voltage. Use the result to size wires, fuses, and charge controllers.

Sun, angle and payback

Solar Time Calculator

Calculate apparent solar time and solar noon for any location. Enter longitude and date to find when the sun is highest.

Solar ROI Calculator

Calculate your solar panel payback period, 25-year savings, and return on investment. Enter system cost, size, annual kWh from PVWatts, and electricity rate.

Solar Panel Angle Calculator

Find the optimal tilt angle for your solar panels by latitude and season. Maximize energy output with the right panel angle.