01 / STORED ENERGY
Convert capacity correctly
Watt-hours measure stored energy directly. For a battery bank, watt-hours equal bank voltage multiplied by total bank amp-hours.
Free real-world planning tools
Battery Runtime Calculators
Choose the calculator that matches the label on your battery, power station or appliance. Every tool includes efficiency losses, usable capacity and power-limit checks.
8 specialized calculators2 capacity systems0 sign-ups required
Choose your runtime calculator
Specialized inputs produce better estimates than forcing every battery and appliance into one generic formula.
Live
Power Station Runtime Calculator
Best when your portable power station or solar generator lists capacity directly in watt-hours.
Battery WhAppliance wattsInverter check
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LiveBattery Backup Time Calculator
Use voltage and amp-hours for 12 V, 24 V or 48 V lead-acid, AGM and LiFePO4 battery banks.
Volts × AhChemistry presetsSeries guidance
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LiveRefrigerator Backup Calculator
Accounts for compressor cycling, daily energy consumption, hot-room conditions and startup surge.
kWh/dayDuty cycleStartup surge
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LiveHome Office UPS Runtime Calculator
Build a complete load from computers, monitors, routers and fiber equipment before estimating runtime.
Device builderWh or V × AhPeak check
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LiveSolar Battery Bank Size Calculator
Size an off-grid battery bank from daily energy, autonomy days, chemistry, voltage, temperature and reserve.
kWh + AhSeries/parallelSolar array
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LiveSolar Battery Charging Time Calculator
Estimate peak-sun charging hours from battery SOC, real panel output, controller limits and active loads.
SOC rangeController limitsSolar days
Open calculator → LiveCPAP Battery Backup Runtime Calculator
Estimate overnight therapy time with heating load, AC or DC losses, battery health and a safety reserve.
Heater presetsAC / DC lossNight estimate
Open calculator → LiveGenerator Fuel Runtime Calculator
Estimate gasoline, diesel or propane runtime from usable fuel, electrical load and a model-specific reference rate.
Fuel curveSurge checkRuntime range
Open calculator →Which calculator should I use?
Select what you are trying to size. We will point you to the most relevant tool.
Recommended tool
Power Station Runtime Calculator
Enter the watt-hour capacity shown on the power station and the real appliance load.
Use this calculatorCalculator comparison
Match the tool to the information you already have for the fastest accurate estimate.
| Calculator | Best input | Special adjustment | Use it for |
|---|---|---|---|
| Power Station | Watt-hours | Inverter idle draw | Portable stations and solar generators |
| Battery Backup | Volts and amp-hours | Battery chemistry | Lead-acid, AGM and lithium banks |
| Refrigerator | kWh/day or duty cycle | Heat and startup surge | Fridges and freezers |
| Home Office UPS | Device-by-device watts | Safety margin and peak | Computers and internet equipment |
| Solar Battery Bank | Daily kWh and backup days | DoD, temperature and reserve | Off-grid storage and solar sizing |
| Solar Charging Time | Battery SOC and panel watts | Controller, BMS and active loads | Battery recharge planning |
| CPAP Battery Runtime | Battery Wh and measured CPAP watts | Heating, AC/DC loss, health and reserve | Overnight CPAP backup planning |
| Generator Fuel Runtime | Fuel quantity and connected watts | Load curve, reserve and startup surge | Gasoline, diesel and propane planning |
What makes a realistic runtime estimate?
02 / ACTUAL LOAD
Use operating watts
Nameplate ratings can be maximums. A power meter or energy label usually gives a better everyday load estimate.
03 / REAL LOSSES
Include the missing energy
Usable capacity, inverter efficiency and idle draw reduce runtime before any appliance receives power.
Runtime is not the same as compatibility
A battery may contain enough energy for many hours while its inverter is still unable to start or continuously power the appliance. Every PowerRuntime calculator checks output limits separately from the energy estimate.
Battery runtime calculator questions
Which calculator is most accurate?
The one matching your available data. Use Wh for power stations, volts × Ah for battery banks, and the specialized refrigerator or office tools for variable loads.
Can I use VA as battery capacity?
No. VA describes apparent-power handling, not stored energy. Runtime needs watt-hours or battery voltage and amp-hours.
Why is calculated runtime lower than capacity ÷ watts?
Real systems lose energy through depth-of-discharge limits, inverter conversion and idle consumption.
Are these estimates brand-specific?
No. The formulas are brand-neutral. Enter specifications from your own battery, inverter, UPS or power station.