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Solar panel size for a gate opener

Free tool by the GateOpenerLab editorial team. Last updated . No sign-up; your answers stay in the page address so you can share the result.

Quick answer

Add up the energy the gate uses in a day (opening cycles plus standby draw), then divide by your winter peak sun hours and allow for system losses. That gives the panel watts. Size the battery to cover several cloudy days without going below half charge. The calculator below does both.

cycles

One cycle = open and close.

Power per cycle

The typical figure comes from Mighty Mule: a full 12 V, 7 Ah battery gives about 50 cycles, so about 0.14 Ah per cycle. Heavier gates use more.

Always-on standby draw

Example figures from LiftMaster's published control board table. Your opener may differ; use its manual if it lists standby current.

mA

Battery-powered wireless keypads draw nothing from the gate battery.

days

Our starting value; pick more if you get long cloudy spells.

Climate

Products

    Learn more: Solar gate openers explained

    How the calculator works

    A solar gate opener runs from a battery. The panel's job is to put back what the gate used each day, even in winter.

    1. Daily energy. Cycles per day × energy per cycle, plus the standby draw of the control board and accessories running 24 hours.
    2. Panel. Daily energy ÷ peak sun hours for your state, with 14.000000000000002% knocked off for system losses (the PVWatts default).
    3. Battery. Daily energy × the days you want to cover, divided by 50% depth of discharge so a lead-acid battery is never run below half. Cold winters double it.

    The formulas

    • Wh per cycle = volts × motor amps × (2 × one-way seconds) ÷ 3,600
    • daily Wh = cycles × Wh per cycle + volts × standby amps × 24
    • panel W = daily Wh ÷ (sun hours × 0.86)
    • battery Ah = daily Wh × days × cold factor (2 if cold) ÷ (0.5 × volts)

    Peak sun hours come from the NLR (formerly NREL) solar resource data: the average daily solar energy on a south-facing panel tilted at your latitude, measured at your state capital. One peak sun hour is one hour of full 1,000 W/m² sun.

    Limits of this tool

    • One point per state (the capital). Mountains, coast fog and shade from trees or buildings can change your sun a lot.
    • The "typical opener" figure is a rough average from one maker. Efficient openers use much less per cycle; heavy gates use more. LiftMaster's own solar chart, for example, shows some of its openers doing far more cycles on a 10 W panel than this calculator would suggest.
    • Motor start-up surges, slow-start features and gate drag are not modeled.
    • The battery math assumes lead-acid (AGM or flooded). Lithium batteries allow deeper discharge but need a compatible charger.
    • Alaska is not covered by the NLR dataset we use; enter your own sun hours there.

    Frequently asked questions

    What size solar panel do I need for a gate opener?

    For a light home gate used about 10 times a day in a sunny state, the math often lands under 10 watts. Busy gates, heavy gates, northern winters and power-hungry accessories push it to 20, 40 watts or more. Enter your numbers above for your own result.

    Why does the calculator use the worst month instead of the yearly average?

    A solar gate has to work in December, not just on average. Sizing for the month with the least sun keeps the battery from running flat in winter. You can switch to the yearly average to see the difference.

    How big should the battery be?

    Big enough to run the gate through several cloudy days without dropping below half charge. The calculator multiplies your daily use by the days you choose and divides by 50% depth of discharge, the top of the range a lead-acid battery maker recommends.

    Does cold weather matter for a solar gate opener?

    Yes. LiftMaster says long spells below −4 °F cut daily cycles and standby time by at least half. Tick "cold winters" and the calculator doubles the battery to cover that.

    Where do I find my opener’s power use?

    Look in the manual for motor current (amps) and travel time, or a solar chart from the maker. If the maker publishes a solar cycles chart for your model, trust it over any general calculator, including this one.

    Can I add a solar panel to an AC gate opener?

    Not directly. AC openers run on 115/120 V from the grid. Solar setups use low-voltage DC openers with a battery that the panel charges. Some makers sell DC versions of their openers for this.

    Sources for the numbers