Step 1: Enter Your Appliances

The calculator comes preloaded with 5 common appliances (LED lights, refrigerator, TV, air conditioner, and laptops) to get you started. You can edit, remove, or add to these.

For each appliance, enter:

• Appliance name — type a custom name, or use the preset dropdown at the top of each row to pick from 17 common devices. Selecting a preset auto-fills the name and wattage for you.
• Quantity — how many of this appliance you have (e.g. 10 LED lights).
• Watt — the power rating in watts. Check the label on your appliance or its manual. The preset dropdown fills this automatically for common devices.
• Hours (Day) — how many hours per day this appliance runs during sunlight hours.
• Hours (Night) — how many hours per day it runs after sunset.

The calculator converts your entries into kWh (kilowatt-hours) automatically and shows daytime, nighttime, and total consumption for each row.

Tip: Day + Night hours for a single appliance cannot exceed 24. The calculator highlights the fields in red if you exceed this limit.

Use the Add Appliance button to add a blank row (pre-filled with Qty: 1, Day: 1h, Night: 0h so you only need to pick the device and wattage). Use Reset to Defaults to go back to the original 5 appliances.

Step 2: Configure Your System Settings

Below the appliance table, you’ll find six settings that control how the system is sized. Each has an ⓘ tooltip — hover over it for a quick explanation.

• Panel Wattage (W) — the rated wattage of a single solar panel you plan to use. Pick a common size from the dropdown (100W–700W) or type a custom value. Default: 600W.
• Battery Voltage (V) — your battery bank voltage: 12V, 24V, or 48V. Higher voltage means lower current and thinner cables. Default: 24V.
• Average Sun Hours — the peak sun hours per day for your location. This is not total daylight hours — it’s the equivalent hours of full-intensity sunlight. Look up your location on the Global Solar Atlas for an accurate number. Default: 5 hours.
• Battery Type — choose between Lithium (LiFePO4) or Lead-Acid (AGM/GEL). This automatically adjusts the depth of discharge and efficiency used in the battery calculation. Lithium allows 80% discharge with 95% efficiency; lead-acid allows only 50% with 85% efficiency. Default: Lithium.
• Autonomy Days — how many days of backup your batteries should provide without any solar charging. 1 day covers one night; 2 days gives you a buffer for cloudy weather. Off-grid systems should use at least 1.5–2 days. Default: 1 day.
• System Losses (%) — accounts for wiring losses, inverter inefficiency, dust, heat derating, and panel mismatch. The default of 25% works for most installations. Increase to 30–35% in hot or dusty climates. Default: 25%.

Step 3: Read Your Results

All results update instantly as you change any input. The System Summary shows six key values at a glance — hover over any box to see an explanation of how it was calculated.

• Solar Panels — the number of panels needed, plus total array wattage. Panels are sized to cover your full daily consumption (day + night) with the loss factor applied.
• Daily Production — estimated energy your sized panel array will generate per day. This will be higher than your consumption because it includes the loss buffer.
• Daily Consumption — your total daily energy usage (daytime + nighttime combined).
• Battery Bank — required storage capacity in kWh and Ah. Accounts for your chosen battery type (DoD and efficiency), autonomy days, and battery voltage.
• Inverter — minimum inverter capacity in kW. Sized by your peak simultaneous appliance load with a 30% safety margin for motor startup surges. We recommend a pure sine wave inverter.
• Charge Controller — MPPT charge controller rating in amps, sized for your total panel wattage and battery voltage with a 25% safety margin.

What the Numbers Mean

• kWh (kilowatt-hours) is a measure of energy — how much electricity is used over time. 1 kWh = running a 1,000W appliance for 1 hour.
• Ah (amp-hours) is battery capacity at a specific voltage. The same energy stored at a higher voltage requires fewer amp-hours.
• Panels are always rounded up to the next whole number — you can’t buy half a panel.
• Inverter (kW) is rounded up to the next whole kilowatt so you have headroom for startup surges.
• Charge Controller (A) is the MPPT controller current rating. For large systems, you may need multiple controllers in parallel.

Tips for the Best Results

Be honest about usage hours. It’s tempting to underestimate how long the AC runs or how often the kids leave lights on. Round up slightly for a more realistic calculation.

Look up your real sun hours. This single number has the biggest impact on how many panels you need. Use the Global Solar Atlas or NASA POWER database rather than guessing.

Choose the right battery type first. Switching between lithium and lead-acid changes the battery bank size dramatically. Decide on your battery chemistry before finalizing the system.

Don’t skip autonomy days. If you’re going off-grid, 1 day of autonomy gives you zero margin for cloudy weather. Even 1.5 days makes a big difference in reliability.

Use the System Summary tooltips. Hover over any result box to see exactly what it means and how it was calculated. If a number seems too high or too low, the tooltip helps you understand why.

Want to understand the formulas behind the numbers? Visit our How It Works page for the complete calculation breakdown.