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Solar calculators that give you a straight answer

Size your solar panels, battery bank and inverter, estimate savings and payback, and check your net-metering bill – in seconds, with the formulas shown. No sign-up, nothing sent to a server.

How many panels do I need?How much will I save?

All solar calculators

Every tool runs in your browser, updates as you type and lets you copy or share the result.

System sizing

How big a system, battery bank or inverter do you need?

Solar Panel CalculatorSize your system: kW, number of panels, roof area and yearly output from your bill or kWh.kWh to Solar Panels ConverterQuick converter: monthly kWh → number of solar panels and system size.Solar Battery CalculatorWork out battery bank capacity in Ah and kWh plus how many batteries you need for backup.Solar Inverter Size CalculatorAdd your appliances and get the right inverter size, accounting for motor start-up surge.Solar Panel Angle CalculatorOptimal fixed tilt, seasonal angles and azimuth for your latitude, with one-click geolocation.

Money & bills

Savings, payback and what your bill looks like with net metering.

Solar Savings CalculatorSee yearly savings, payback period and 25-year return with a simple cumulative-savings chart.Solar Payback CalculatorBreak-even year, net cost after incentives and 25-year profit for your solar investment.Net Metering CalculatorImport vs. export units and buy/sell rates → your monthly bill, credits and savings.

Electrical design

Cable sizing and reference data for a safe installation.

Solar Wire Size CalculatorRecommended AWG and mm² cable size from current, voltage, run length and allowed voltage drop.Appliance Wattage ListRunning watts, surge factors and typical daily hours for 80+ household appliances.

Electrical unit converters

Quick two-way conversions with the formula and worked examples on every page.

How to size a solar system in three steps

1
Know your usage
Find the kWh on your electricity bill (or use our appliance wattage list to add it up). Everything starts from daily kWh.
Appliance wattage list →
2
Size the hardware
Panels from your sun hours, batteries from your backup hours, inverter from the loads you run together.
Solar panel calculator →
3
Check the money
Project yearly savings, payback period and 25-year return, then sanity-check the net-metering bill.
Payback calculator →

Solar guides

All articles →

Sep 12, 2026 · 5 min read

How to Size an Off-Grid Solar System Step by Step

A complete step-by-step method for sizing an off-grid solar system: load audit, battery bank, array, inverter, wiring, and safety, with worked examples.

Sep 7, 2026 · 4 min read

What Are Peak Sun Hours? How to Find Yours and Why They Matter

Peak sun hours drive every solar sizing calculation. See what they mean, typical values for cities worldwide, and how tilt and season change your number.

Sep 2, 2026 · 5 min read

Solar Payback Period Explained (With Worked Examples)

Learn how solar payback period is calculated, see three worked examples across different climates and tariffs, and avoid the most common mistakes people make.

Formulas you can check

Every calculator shows exactly how the result is computed and which assumptions it makes.

Global sun-hours data

Built-in peak sun hours for 200+ cities and 70+ countries, plus manual entry for anywhere else.

Private by design

Inputs never leave your browser. Share links only contain the numbers you typed.