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Starlink battery runtime calculator

How long a battery runs a Starlink dish with no sun, how many watt-hours the dish eats per day, and how big a bank you need to run it around the clock. Dish figures are the averages Starlink prints on its own spec sheets, linked below.

Inputs

Dish

Sheet is titled "Standard 4 X"; the figure includes the Gen 3 router and power supply.

Starlink publishes no heater figure. On uses the top of the published range (100 W); off uses the midpoint (87.5 W). Override below if you have a meter reading.

Starlink's figure covers the antenna, its router and the power supply.

Laptop, monitor, a second router, lights. Leave at 0 to size for the dish alone.

Battery and inverter
Battery capacity

1,200 Wh nominal. Use the nameplate number; the reserve below is where you account for what you will not drain.

100 if the dish runs on DC.

Share of the bank you keep. 20 is typical for LiFePO4, 50 for lead-acid.

Results

Runtime 9 h 52 min. 2,333 watt-hours per day. 2.92 kilowatt-hours needed for 24 hours.

Runtime on this battery
9 h 52 min

960 usable Wh ÷ 97.2 W from the battery, no sun and no charging.

Draw from battery
97.2 W

88 W of load ÷ 90% inverter.

Energy per day
2,333 Wh

2.33 kWh every 24 h, which your solar has to put back.

To run 24 h you need
2.92 kWh≈ 243 Ah at 12 V

Nameplate capacity, with your 20% reserve left untouched at the end of the day.

How we computed this

  1. Load.Dish watts plus whatever else is on the battery. Heater off uses the midpoint of Starlink's published range; heater on uses the top of it.
  2. Battery watts = load ÷ inverter efficiency. A 90 % inverter turns 88 W of AC load into about 98 W pulled from the bank. If the dish runs on DC (Mini, or a Gen 3 with a DC conversion kit) set efficiency to 100.
  3. Usable Wh = nameplate Wh × (1 − reserve). Ah is converted at the nominal voltage you pick: 100 Ah at 12 V is 1,200 Wh.
  4. Runtime = usable Wh ÷ battery watts. This is the no-sun, no-generator number.
  5. Wh per day = battery watts × 24. Bank for 24 h = Wh per day ÷ (1 − reserve), so the reserve is still there in the morning.

The same arithmetic, fed by live inverter and dish data instead of typed numbers, is the “hours at current state of charge” answer in deadzone, the open-source Go binary I run in the shed.

Caveats

  • Starlink publishes a range, not a number. “Average: 75–100 W” is all the Standard sheet says. Real draw moves with satellite handoffs, obstruction, weather and firmware. Owners with plug-in meters commonly report Gen 3 Standard kits below the published range when idle and above it in rain or snow; put your own meter reading in the dish-draw field.
  • There is no published heater wattage. The toggle only moves you to the top of Starlink's range. In a real storm with snow melt on, expect more than that and plan for it.
  • Nameplate Ah is not usable Ah. Cold LiFePO4 delivers less, lead-acid loses capacity at high discharge rates, and BMS low-voltage cutoffs land above zero. The reserve field is the only margin here; it does not model temperature or ageing.
  • Inverter idle draw is not included. Many inverters burn 15–60 W doing nothing. If yours is on only for the dish, add its idle draw to “other loads”.
  • Sleep schedule changes everything. Starlink's app can power the dish down overnight; this tool assumes it runs continuously.
  • This is arithmetic, not advice. Verify against your own system before you depend on it for a call you cannot miss.