Battery Bank Wattage Calculator
Calculate total and usable watt-hours for your battery system
Battery Bank Wattage Calculator
For Solar, RV, and Off-Grid Systems
Results:
Total Watt-hours (Wh): 0.00
Usable Watt-hours (Wh): 0.00
How to Use the Battery Bank Wattage Calculator
Basic Calculation
- Enter Battery Voltage (V)
- Enter Battery Capacity (Ah)
- Default DoD and Inverter Efficiency will be used
With Depth of Discharge
- Enter Voltage and Capacity
- Adjust Depth of Discharge (DoD %)
- This impacts usable capacity
With Inverter Efficiency
- Enter Voltage, Capacity, and DoD
- Adjust Inverter Efficiency (%)
- Accounts for energy loss during conversion
How to Calculate Battery Bank Wattage
Use this workflow to recreate the calculator output whenever you need a quick watt-hour check in the field.
Step 1: Capture Voltage & Capacity
List the nominal bank voltage (12 V, 24 V, 48 V, etc.) and the total amp-hours after accounting for series and parallel strings.
- Multiply the number of parallel strings by the Ah rating of each string.
- Confirm the system voltage that matches your inverter or DC loads.
- Note the chemistry (AGM, flooded, lithium) because it determines safe DoD.
Step 2: Set Depth of Discharge & Efficiency
Pick the allowable depth of discharge (DoD) for cycle life and the inverter or DC-DC efficiency for your load path.
DoD factor = DoD % ÷ 100 | Efficiency factor = ηinv ÷ 100
Step 3: Run the Watt-hour Formula
Multiply voltage by amp-hours to get the theoretical energy stored in the bank.
Whtotal = Battery Voltage × Battery Capacity
Step 4: Convert to Usable Output
Apply DoD and efficiency to see what can be delivered to the load without shortening battery life.
Whusable = Whtotal × (DoD ÷ 100) × (Efficiency ÷ 100)
For lithium banks you can often use 80-90% DoD, while lead-acid is usually limited to 50%.
Step 5: Translate Watts to Runtime
Divide the usable watt-hours by the load wattage to estimate run time or size additional strings.
Runtime (h) = Whusable ÷ Load (W)
Add 10-15% margin for inverter surge losses or temperature derating.
Battery Bank Wattage Chart
Values assume 80% depth of discharge and 90% inverter efficiency for AC loads. Round to the next size if your loads have heavy surge currents.
| Battery Setup | Voltage (V) | Capacity (Ah) | Total Watt-hours | Usable Watt-hours* | Typical Application |
|---|---|---|---|---|---|
| Compact RV starter bank | 12 | 100 | 1,200 Wh | 864 Wh | LED lighting, fans, routers for ~8 hours |
| Dual 12 V 100 Ah in parallel | 12 | 200 | 2,400 Wh | 1,728 Wh | Trolling motor or ham radio setups needing a full day |
| 24 V lithium wall-mounted pack | 24 | 150 | 3,600 Wh | 2,592 Wh | Telecom cabinets or small office backup |
| 24 V deep-cycle string (5 × 120 Ah) | 24 | 250 | 6,000 Wh | 4,320 Wh | Well pumps and critical household loads overnight |
| 48 V rack battery (4 modules @ 50 Ah) | 48 | 200 | 9,600 Wh | 6,912 Wh | Hybrid inverter systems around 5-6 kW |
| 48 V server rack (LiFePO4 280 Ah) | 48 | 280 | 13,440 Wh | 9,680 Wh | Whole-home solar storage or microgrid battery |
*Usable watt-hours shown after applying 0.8 DoD and 0.9 inverter efficiency. Adjust the multipliers to match your system design limits.
Battery Bank Wattage FAQs
Quick conversions between milliamp-hours, watts, and watt-hours for the most common portable-bank questions.
How many watts is a 20000mAh power bank?
Use Wh = (mAh ÷ 1000) × Vnominal. Most USB banks use 3.7 V cells, so 20,000 mAh × 3.7 V ~ 74 Wh. After boost conversion to 5 V USB at ~90% efficiency you get roughly 66 Wh, which can power a 13 W load for about 5 hours.
How many watts is a 10000mAh battery?
A 10,000 mAh pack at 3.7 V stores about 10,000 × 3.7 ÷ 1000 = 37 Wh. Expect ~33 Wh of usable energy after conversion losses, enough for a 10 W tablet for just over 3 hours.
How many watts is a 1000 mAh battery?
1,000 mAh equals 1 Ah. At 3.7 V the stored energy is roughly 3.7 Wh, so you can supply 3-4 W for one hour or 1 W for about four hours before factoring inverter or regulator losses.
How many mAh is 200 watts?
You must know the voltage and run time. Rearrange the formula to mAh = (W × hours × 1000) ÷ V. Example: a 200 W load for 1 hour on a 12 V battery requires (200 × 1 × 1000) ÷ 12 ~ 16,700 mAh (16.7 Ah). The same load on 24 V only needs about 8,300 mAh.
What is a 5000 mAh battery in watts?
Convert to watt-hours: 5,000 mAh × 3.7 V ÷ 1000 ~ 18.5 Wh. Accounting for regulator efficiency you can expect 16-17 Wh of usable energy, which equals 5 W for roughly 3 hours.