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☀️ Solar Off-Grid System Calculator

🔌 Appliance Input

(Device name)
(Number of same devices)
(Hours/day used)
(Watts on device label)
(Appliances with motors need larger inverters)
Click to add another device. Results will appear below the table under Total Daily Load.
ApplianceQtyHoursWattsSurge?Daily WhAction
Total Daily Load: 0.00 Wh

⚙️ System Configuration Fill In The Following Details To Get System Requirements

(Sun hours/day, 3-6 typical)
(Panel power rating)
(Wiring, temperature, dust losses)
(Higher voltage = less current)
(1-3 typical, 7+ requires large battery)
(DC to AC conversion efficiency)
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Easy Guide: How to Use the Solar Energy Calculator.

Want to go solar but not sure how many solar panels or batteries you need? This calculator helps you figure it out in minutes—even if you’re not an expert.

Step 1: List Your Appliances (What You Want to Power).

You’ll start by entering all the devices you want to run using solar power—like lights, TV, fridge, or phone charger. For each device, you’ll enter:

  • Appliance Name – What is the device called? (e.g., “TV” or “Fridge”.)

  • Quantity – How many of that device do you have?

  • Daily Usage (Hours) – On average, how many hours per day do you use it?

  • Power Rating (W) – This is the electricity it uses. You’ll find this on a sticker on the device (e.g., “60W” for a light bulb). Check common used devices power rating in kenya HERE.

Example:

  • Appliance: Fridge.

  • Quantity: 1.

  • Daily Usage: 24 hours (it runs all day).

  • Power Rating: 700W.

The calculator will then automatically calculate the energy it uses per day. (We call this Watt-hours, or Wh.)

Daily Watt-hours (Wh) = Quantity × Daily Hours × Power Rating.

Step 2: See Your Total Energy Use.

After entering all your appliances, the calculator shows you:

  • Total Daily Load (Wh) – This is the total amount of electricity you need every day.

Think of this like your “solar shopping list”—how much power your system must provide each day.

Step 3: Enter Solar System Settings (Customize Based on Your Location).

Now tell the calculator a few things about your solar setup.

  • Sun Hours (per day).
    ➤ How many hours of strong sunlight your location gets per day.
    (Tip: Most of Kenya gets 4–6 hours. You can get details about your area HERE.)

  • Solar Panel Power (W). What to Enter for Solar Panel Power (W)?

    This is the power rating of one solar panel, in watts (W). It tells you how much electricity that panel can produce in one hour of good sunlight. If you’re not sure, just enter: 300W (This is the most commonly used panel size in Kenya and many other countries.)

    Most home solar systems today use panels that are between 250W and 550W, but 300W is a safe and typical value to get a good estimate.

  • ➤ How powerful is each solar panel?
    (Example: A 300W panel means it gives 300 watts per hour in good sun.)

  • System Load Factor (%)
    ➤ This is just a safety margin to handle energy losses—like dust on panels or cloudy days.
    (Use 20%–30% here. The calculator does the math for you.)

  • Battery Voltage (V).
    ➤ Most common are 12V, 24V, or 48V.
    (24V or 48V is better for big systems—it reduces energy loss.)

Step 4: Backup Battery & Inverter Settings.

If you want your system to keep running during cloudy days, fill in these:

  • Days of Autonomy.
    ➤ How many days should the battery last without sun?
    (2 days = safe for rainy seasons.)

  • Inverter Efficiency (%).
    ➤ This tells us how well the inverter converts solar energy to usable electricity.
    (Most are 85–95%. Use 90% as a good average.).

Step 5: View Your Solar System Requirements.

After entering everything, the calculator shows:

  • How many solar panels you need.

  • What size batteries you need (in Amp-hours or Ah).

  • The right inverter size (in watts or VA).

Example Output:

  • Daily Energy Needed: 16,800 Wh.

  • Solar Panels Needed: 18 panels (300W each).

  • Battery Storage Required:

    • Lead Acid Battery: 2,365 Ah.

    • Lithium Battery: 1,295 Ah.

  • Inverter Size: Around 3,000–5,000W (depending on peak load).

What the Terms Mean (Simple Definitions).

TermWhat It Means
Wh (Watt-hours)Total energy used in a day (like litres of fuel).
W (Watts)Power rating of a device (like engine size).
Ah (Amp-hours)Battery storage capacity (like tank size).
V (Volts)Battery or system voltage (higher = better for big systems).
VA (Volt-Amps)Inverter capacity – how much load it can handle.
System Load FactorExtra margin to cover energy losses.
Inverter EfficiencyHow well your inverter works (usually 85–95%).
Days of AutonomyHow long batteries can power your home without sun.

Final Tips:

  • Start by calculating only the most important appliances.

  • Use higher battery voltage (like 24V) for bigger systems—it’s more efficient.

  • Confirm your average sun hours using a trusted weather source or solar installer.

  • Don’t worry if you’re not 100% sure—this tool gives an estimate to help you plan.