Solar Battery Sizing Calculator
Battery bank size for days of autonomy.
Enter your values
Enter the daily energy use in kWh.
Enter the days of autonomy you are working with.
Enter the depth of discharge in %.
Enter the round-trip efficiency in %.
Enter the system voltage in V.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Battery bank size
- 23.61 kWh
- Amp hours at system voltage
- 492
- Usable energy
- 18.89 kWh
- Cost estimate at $400/kWh
- $9,444.44
Quick answer
Battery bank size must cover daily load across your autonomy days without exceeding depth of discharge.
Capacity = load × days ÷ (DoD × efficiency)
At a glance
| What it does | Battery bank size for days of autonomy. |
|---|---|
| Category | Technology |
| Inputs needed | Daily energy use, Days of autonomy, Depth of discharge, Round-trip efficiency, System voltage |
| Main output | Battery bank size |
| Formula | Capacity = load × days ÷ (DoD × efficiency) |
| Cost | Free — no sign-up, no download |
How to use the Solar Battery Sizing Calculator
- 1Enter your daily energy consumption.
- 2Choose days of autonomy without sun.
- 3Set depth of discharge for your battery chemistry.
Inputs explained
- Daily energy use(kWh)
- Enter the daily energy use in kWh.
- Days of autonomy
- Enter the days of autonomy you are working with.
- Depth of discharge(%)
- Enter the depth of discharge in %.
- Round-trip efficiency(%)
- Enter the round-trip efficiency in %.
- System voltage(V)
- Enter the system voltage in V.
Worked example
Using the values the calculator loads with:
Inputs
- Daily energy use8.5 kWh
- Days of autonomy2
- Depth of discharge80 %
- Round-trip efficiency90 %
- System voltage48 V
Results
- Battery bank size23.61 kWh
- Amp hours at system voltage492
- Usable energy18.89 kWh
- Cost estimate at $400/kWh$9,444.44
Frequently asked questions
What DoD for lithium?
80–90% is safe for LiFePO4; lead acid should stay near 50%.
How many autonomy days?
Two is typical; three for remote sites.
What do I need to enter into the Solar Battery Sizing Calculator?
Just 5 values: daily energy use, days of autonomy, depth of discharge, round-trip efficiency, system voltage. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Solar Battery Sizing Calculator work out the answer?
Battery bank size must cover daily load across your autonomy days without exceeding depth of discharge. It applies the formula Capacity = load × days ÷ (DoD × efficiency) and shows the working so you can check each step by hand.
Is the Solar Battery Sizing Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.