How much power does Starlink use on a boat?

The Flat High Performance antenna averages 50 to 75 watts, with peaks to 110 watts when heaters are active. The Maritime antenna averages 90 to 110 watts, peaking at 150 watts. At 12V, that translates to roughly 100 amp-hours per day for Flat High Performance running 24/7, and 180 amp-hours per day for Maritime.

Will Starlink drain my house batteries overnight?

On a typical 400 to 600 amp-hour lithium house bank, no. Starlink will use 30 to 50 amp-hours overnight depending on antenna and use pattern — well within usable capacity. On a smaller AGM or flooded bank, the math is tighter and we recommend pausing the antenna overnight or sizing solar to cover the day's draw.

How much solar do I need to run Starlink at anchor?

For Flat High Performance running 24/7 at anchor, plan for 400 to 600 watts of solar in northern latitudes — Connecticut, New England — or 300 to 400 watts in Florida and the Caribbean. For Maritime, double those numbers. Lithium house bank is recommended either way for the discharge depth and cycle life.

Should I turn Starlink off when not using it?

On a well-sized house bank with solar, no — leave it on, the convenience is worth the few amp-hours. On a smaller bank without solar, yes, switch it off when leaving the boat or sleeping. Most installs include a dedicated DC switch at the helm or panel for this.

Does Starlink draw more power in cold weather?

Yes — modestly. The integrated heaters that melt snow and ice on the antenna activate below freezing, adding 30 to 50 watts of intermittent draw. In a Connecticut December, daily consumption can climb 20 to 30 percent. Worth accounting for if the boat lives in the water year-round.

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May 2026

Starlink power draw on a boat — measured numbers, house-bank math, and solar sizing that actually works.

"Will Starlink kill my batteries?" is one of the most-asked questions on the Sound. The honest answer is no, on most boats — but the math is worth doing once, properly. Here are the numbers we measure on real installs and the sizing rules we use.

5 min read Install Guides, Hardware, Troubleshooting

Starlink's published power numbers are honest but rounded. On a boat, what matters is not the spec sheet — it is the actual amp-hours drawn over a real day on the hook, factoring in idle, active use, and the heater cycles that fire below freezing. We measure that on every install at handoff, and the numbers below are what we see across a season of Connecticut deployments.

This article does the house-bank math from first principles. By the end, you will know what Starlink actually costs in amp-hours on your boat, whether your existing bank can handle it, and what to add — solar, lithium, or both — if it can't.

"Spec sheets are honest but rounded. Boats run on amp-hours, not averages."

Measured draw

What we read at the meter on real installs.

The most useful numbers are the ones we measure with a clamp meter on commissioned boats. Across 40-plus Connecticut installs, the picture is consistent.

Flat High Performance — idle.40 to 50 watts. Antenna locked, no traffic, ambient temperature.
Flat High Performance — active use.55 to 75 watts. Streaming, video calls, mixed traffic.
Flat High Performance — heater active (cold weather).90 to 110 watts intermittent.
Maritime / High Performance — idle.80 to 95 watts.
Maritime / High Performance — active use.100 to 130 watts.
Maritime — heater active.140 to 150 watts intermittent.
Indoor router (Gen 3).5 to 10 watts continuous. Basically a rounding error.

For the wiring side that turns these watts into clean DC, see our DC wiring article. The numbers above assume DC-direct wiring; the inverter path adds 10 to 20 percent.

Daily amp-hours

What that draw turns into over 24 hours at 12V.

Boats budget power in amp-hours, not watts. The conversion is simple — watts divided by voltage equals amps, multiplied by hours equals amp-hours. Done across a typical 24-hour day, the picture sharpens.

Flat High Performance, 24/7 at anchor, mixed use.~60W average × 24h = 1,440 watt-hours = 120 amp-hours/day at 12V, or 60 amp-hours/day at 24V.
Flat High Performance, 12 hours active + 12 hours off.~30W average × 24h = 720 watt-hours = 60 amp-hours/day at 12V.
Maritime, 24/7 at anchor, mixed use.~100W average × 24h = 2,400 watt-hours = 200 amp-hours/day at 12V, or 100 amp-hours/day at 24V.
Cold-weather adjustment.Add 20 to 30 percent for any month with freezing nights — the heaters cycle.

Those are the numbers to plan against. Owners who sleep aboard with Starlink running and other house loads typically end the night down 80 to 130 amp-hours from full. House-bank sizing follows from there.

House-bank sizing

What capacity you actually need to run Starlink overnight.

Lithium and AGM behave differently — usable capacity is the real number, and lithium gives you 80 to 90 percent of nameplate while AGM gives you 50 percent before the bank starts to suffer.

200Ah lithium bank, Flat High Performance, mixed daily use.Sufficient for a single overnight at anchor with refrigeration and lights. Tight on a second night without recharge.
400Ah lithium bank.Comfortable for two to three nights of Starlink-on plus normal house loads. The most common sizing on Connecticut boats we install.
600Ah+ lithium bank.Liveaboard territory. Comfortable indefinitely with solar topping up daily.
400Ah AGM bank.Equivalent to 200Ah usable. Tight for Starlink-on overnight unless you discharge below 50 percent (and shorten the bank's life).

The honest summary: if you have a modern lithium bank in the 400Ah range, you're fine. If you have an aging AGM bank under 400Ah, Starlink is a real load and you should plan accordingly.

"Lithium gives you 90 percent of nameplate. AGM gives you 50. The math diverges fast."

Solar sizing

Watts of panels needed to keep up with the antenna.

Solar is the cleanest solution to Starlink's draw — match generation to consumption and the bank stays full indefinitely. The panel sizing depends on latitude and antenna tier.

Connecticut / Northeast, Flat High Performance, 24/7 use.400 to 600 watts of solar, ideally on a hard mount or arch (not a flexible glued panel). Generates 1,500 to 2,400 watt-hours on a sunny day — enough to cover the antenna and most house loads.
Connecticut, Maritime, 24/7 use.800 to 1,000 watts of solar. Tight to find space on a 50-foot boat without a full hardtop array.
Florida / Caribbean, Flat High Performance.300 to 400 watts. Higher solar yield per watt, longer days.
Cloudy-day reserve.Plan for 30 percent panel output on overcast days. The bank covers the deficit; the next sunny day refills.

Owners running Starlink off solar at anchor often find the system pays for itself in marina fees — a properly sized solar/lithium/Starlink stack means more nights at anchor and fewer at $5/foot/night slips.

When to add an inverter — and when not to

Inverter sizing for Starlink: usually unnecessary.

The cleanest Starlink install is DC-direct, no inverter. We covered the wiring side in our DC wiring article. Owners sometimes ask if the existing 2,000W inverter the boat already has can run Starlink. The answer is yes, but there's a real cost.

Inverter losses.10 to 20 percent. On a 60W antenna, that's 6 to 12 extra watts pulled from the bank, every hour, for the life of the install.
Inverter idle draw.Most boat inverters draw 8 to 25 watts just sitting on, even with no AC load. If the inverter is left on for Starlink, that idle draw adds up.
Right answer.DC-to-DC step-up converter, 90 percent efficient, no idle draw. Standard Helm install.

If the boat already has a 24V or 48V house bank — common on larger yachts — the conversion is even simpler. 24V to 48V is a small step-up; 48V can sometimes feed Starlink directly with a fuse and a buck regulator.

Worked example

A 45-foot Connecticut powerboat, weekends and the occasional anchor-out.

Concrete numbers help. Here is the full math for a typical boat we install on.

Boat.45-foot powerboat, 12V house system, 400Ah lithium bank, 200W of arch solar, Flat High Performance antenna.
Daily Starlink draw.~120 amp-hours over 24 hours of mixed use.
Other house loads.~80 amp-hours (refrigeration, lights, electronics).
Total daily draw.200 amp-hours.
Solar generation, sunny day.~80 amp-hours (200W × 5 hours / 12V × derate factor).
Net daily depletion.120 amp-hours — well within the 360 amp-hours of usable capacity in a 400Ah lithium bank.
Recharge.2 to 3 hours of engine run or shore power covers a full day's deficit.

The bank handles two nights at anchor before needing a recharge. Adding 200 to 400 more watts of solar makes the bank net-positive on sunny days and pushes the at-anchor envelope to a week or longer.

Conclusion

Starlink is a real load. It is not a problem.

The honest summary: on a modern boat with a lithium house bank in the 400Ah range and modest solar, Starlink running 24/7 is a normal load. It does not kill batteries. It does not require an inverter. It does not require an electrical refit. On older boats with smaller banks and no solar, the math is tighter and the right answer is to add solar or pause the antenna overnight — same as any other real load.

Tell us about your boat's electrical system and we'll map the right install around it. Welcome aboard.

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