Solar Battery Runtime Calculator
Estimate battery runtime from nominal kWh, load watts, depth of discharge, inverter efficiency, and standby draw.
Enter system values
Estimate how long a battery can run a given load after depth-of-discharge, inverter losses, and standby draw.
Results update locally in your browser. Raw inputs/results are not stored, logged, placed in URLs, or sent to analytics.
Solar planning sanity check
Use these rows to check assumptions before buying panels, batteries, inverter, controller, or cable.
Educational estimate only. Verify electrical code, permits, equipment manuals, fuse/breaker sizing, and qualified installation requirements before using results in a real system.
What this means
A 5.12 kWh battery at 80% DoD and 92% efficiency runs a 615 W load for about 6.13 hours.
| Item | Value |
|---|---|
| Battery usable energy | 3768.32 Wh |
| Load including standby | 615 W |
| Estimated runtime | 6.13 hours |
- Value
- 3768.32 Wh
- Value
- 615 W
- Value
- 6.13 hours
Copy / print
Copy or print this local-only worksheet. Values are not stored by CalcShelf.
Watch-outs
- Battery capacity changes with temperature, age, and discharge rate.
- Lead-acid usable capacity falls at high loads.
- Inverter standby draw matters for small overnight loads.
Safety boundary
Runtime changes with battery age, temperature, discharge current, and inverter standby draw. Treat these outputs as planning estimates, not installation instructions.
Displayed numbers are rounded to 2 decimal places where helpful.
Use the Solar Battery Runtime Calculator for the right job
Use this when you have a battery size and want to know how long it can run a specific load or backup scenario.
Good for
- Backup runtime estimates
- Battery bank comparison
- Checking whether standby draw matters overnight
How to use it
- Enter battery kWh and load watts.
- Set usable depth of discharge and inverter efficiency.
- Add standby watts if the inverter or system has idle draw.
What changes the result
- Battery nominal kWh
- Usable depth of discharge
- Load watts
- Inverter efficiency
- Standby or idle draw
Next calculators to check
Solar Battery Bank Size Calculator
Size the battery bank first.
Generator + Solar Backup Runtime Calculator
Add solar and generator support.
Solar Load Calculator
Refine the load watts.
FAQ
How long will a solar battery run my load?
Usable watt-hours divided by total load watts gives runtime hours. Usable watt-hours should account for depth of discharge and inverter efficiency.
Why is actual battery runtime shorter than the label suggests?
Nominal battery capacity is not always fully usable. Inverter losses, depth-of-discharge limits, temperature, age, high current, and standby loads reduce runtime.
Does this replace a battery datasheet?
No. Use it as a planning estimate before buying parts, then verify the design against equipment manuals, electrical code, fusing, conductor ratings, permits, and qualified installation advice.
Safety and accuracy notes
Solar and battery systems can involve high DC current, fire risk, permit requirements, electrical code, roof loading, wind loading, temperature derating, fusing, disconnects, and manufacturer limits. Use this as an educational planning estimate only, then verify real designs with qualified sources and equipment manuals.
Get a better answer from the Solar Battery Runtime Calculator
- Start with the example values to see how the tool behaves.
- Swap in your own numbers, even if they are rough first-pass estimates.
- Change one input at a time so you can see what actually moves the result.
What the result means
The result is a planning number for one part of a solar system: load, panels, strings, wire, battery, inverter, controller, mounting, backup, or payback.
How to use it
Use it to compare scenarios before buying hardware, then cross-check the adjacent calculators so one component is not sized in isolation.
What can change it
Solar estimates can move quickly with sun hours, shading, temperature, battery limits, voltage drop, surge loads, roof constraints, utility rules, and code requirements.
Good for
Plan a solar or backup-power system before buying equipment.
Check next
Compare your result with Solar Battery Bank Size Calculator, Generator + Solar Backup Runtime Calculator, Solar Load Calculator when you want more context.
Best habit
Run a conservative case and an optimistic case. The gap between them is often more useful than a single answer.
Common uses
- Plan a solar or backup-power system before buying equipment.
- Check one sizing layer with local-only browser math.
- Pair with adjacent solar calculators for a full system sanity check.
Common questions
Is the Solar Battery Runtime Calculator private?
Yes. CalcShelf calculators run without an account, do not save calculator entries, and do not put raw inputs into shareable URLs or analytics events.
How accurate is the Solar Battery Runtime Calculator?
It is a solar planning worksheet. Sun hours, shading, derating, temperature, fusing, wire ratings, battery limits, permits, and equipment manuals can change the final design.
What should I check after using the Solar Battery Runtime Calculator?
Verify electrical code, fusing, wire ampacity, voltage drop, battery and inverter limits, roof constraints, permits, and manufacturer manuals.
Which calculator should I try next?
Use the related calculators below to cross-check the same decision from another angle before you act.
Method behind the estimate
Solar calculators use load, energy, voltage-drop, battery-capacity, inverter, controller, roof-fit, and payback formulas with bounded user-entered assumptions.
Why the detail matters
Treat the output as a planning worksheet. Electrical code, permits, fusing, disconnects, temperature derating, battery chemistry, roof structure, and manufacturer limits can change the real design.
Privacy guardrail
Your calculator values are for you. CalcShelf does not require an account, save calculator entries, put your numbers into shareable URLs, or use raw inputs as analytics events.
Copy or print safely
Use any copy, print, or worksheet controls as local handoff tools for your own notes, supplier calls, lender questions, or implementation checklist. They are there to help you explain the result to a human.
Before acting
Treat the result as a decision draft, not a verdict. Recheck the source numbers, run a downside case, and verify the real-world rule, quote, label, or spec that controls the final answer.
Last reviewed: May 11, 2026. See methodology and editorial policy for formulas, assumptions, rounding, review approach, and limitations. Before buying or installing solar equipment, confirm electrical code, permits, fusing, wire ratings, battery limits, roof constraints, and equipment manuals.