Off-grid Solar System Sizing Calculator

Easily Calculate Battery and Solar Panel Size for Your Off-Grid Solar System in Kenya.

Our solar energy calculator makes it easy to estimate your daily power needs and shows you the right battery size (Ah), solar panel size (W), and total energy usage (Wh).

How to Use the Off-Grid Solar Sizing Calculator

A Simple Guide for Everyone

Planning to go off-grid? This calculator helps you figure out the right battery size and number of solar panels you’ll need.

Step 1: Enter Your Appliance Usage.

List what you use daily—like lights, fridge, TV—and for how many hours.
Example: A 100W TV used for 5 hours = 500Wh.
Do this for all your appliances. The calculator will total it for you.

Step 2: Choose System Voltage.

Pick 12V, 24V, or 48V depending on your setup.
Tip: Most small homes use 12V or 24V. Larger setups may need 48V.

Step 3: Days of Autonomy.

How many cloudy days do you want your batteries to last without sun?
Example: 2 days of backup means more battery storage.

Step 4: Battery Discharge Level.

This is how much of your battery you’re willing to use.
Tip: For long battery life, don’t go below 50% for lead-acid batteries.

Step 5: Inverter Efficiency.

Inverters aren’t perfect—some energy is lost.
90% is common (meaning 10% of energy is lost during conversion).

Step 6: Average Sunlight Hours.

Enter the average number of sunny hours your area gets per day.
In Kenya, this is usually between 4–6 hours.

What the Calculator Gives You

• Battery Size (Ah): How big your battery bank needs to be.
• Solar Panel Size (W): How much power your panels must produce.
• Total Energy Use (Wh): Your daily energy needs.

Why This Matters

Using this calculator helps you avoid over- or under-sizing your system. You’ll save money, avoid power shortages, and keep your system running longer.

Full Explanation of All Initials & Units.

1. Ah – Amp-hours

This measures battery capacity.
It tells you how many amps (units of electric current) your battery can supply in one hour.

• Example: A 100Ah battery can give 5 amps for 20 hours (5A × 20h = 100Ah)
• Used to estimate how long your battery will last

2. kWh – Kilowatt-hours

This measures total energy usage or storage over time.
It’s the same as the units on your electricity bill.

• 1 kWh = 1,000 Wh
• Example: If a 1,000-watt (1 kW) appliance runs for 1 hour, it uses 1 kWh.

3. Wh – Watt-hours

Also a measure of energy over time, but on a smaller scale.
Used to calculate daily or hourly energy consumption.

• Example: A 100-watt bulb used for 5 hours = 100 × 5 = 500 Wh

4. W – Watts

Watts measure power — the rate at which energy is used or produced.

• For solar panels: how much power a panel can generate
• For appliances: how much power an item needs to run

5. V – Volts

Volts measure electrical pressure or force.
In solar systems, it’s the system voltage (e.g. 12V, 24V, 48V) that matches your inverter and battery.

• Example: A 48V system uses 48 volts across all components.

6. DoD – Depth of Discharge

This tells you how much of the battery’s energy can be used before recharging.

• Lead-acid: max 50% DoD (you only use half the battery)
• Lithium: up to 80–90% DoD (you can use most of it)

7. Inefficiency Factor

This accounts for energy lost during storage, conversion, or transfer.

• Lead-acid batteries typically lose 10–20%
• Lithium batteries are more efficient, with only ~5% loss

📝 Summary Table for Quick Reference