How long will a desktop computer run on a battery?
A desktop computer draws about 300 W. How long it runs depends on your battery's capacity, voltage and chemistry. Adjust the values below for your exact setup — the estimate updates live.
What changes the run-time
Three things move the number: your battery's usable capacity (chemistry sets how much you can safely draw — about 80% for LiFePO4, 50% for lead-acid), the desktop computer's actual power draw (rated watts can differ from running watts, and motors cycle on and off), and inverter losses if you run it on AC. This estimate accounts for usable depth of discharge and typical inverter loss.
To size a complete system around a desktop computer and other loads, use the full system calculator.
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Frequently asked questions
How long will a desktop computer run on a 100Ah 12V LiFePO4 battery?
A desktop computer drawing about 300 W will run roughly 3.0 hours on a 100Ah 12V LiFePO4 battery (using ~80% usable capacity and typical inverter loss). Lead-acid of the same rating gives less, because only about 50% is usable.
How many watts does a desktop computer use?
A typical desktop computer draws around 300 W, though actual draw varies by model and, for motor-driven appliances, cycles on and off.
Sources & standards
- IEEE 1013 — Recommended Practice for Sizing Lead-Acid Batteries for Stand-Alone Photovoltaic Systems — Widely used engineering practice for days-of-autonomy and depth-of-discharge sizing methods, referenced here for the general sizing approach.
- UL 1973 — Batteries for Use in Stationary and Motive Auxiliary Power Applications — Safety standard most LiFePO4 and other stationary/portable battery packs are certified to.
- IEC 60896 — Stationary Lead-Acid Batteries (test & performance requirements) — International test standard covering VRLA (AGM/gel) and flooded stationary lead-acid batteries.
- ENERGY STAR Product Finder — US EPA/DOE database of tested annual/typical energy use for major household appliances.
- U.S. EIA — Electricity Use in Homes — Federal reference on typical household electricity consumption by end use.
Typical device wattage is a planning figure, not a spec for any one model — check the nameplate or manual of your specific unit.
Estimates for planning only. Verify with a meter; see the methodology.