Solar gate openers explained

How a solar gate opener works

A solar gate opener has four parts:

1. A DC operator. A 12 V or 24 V motor and control board, built to run from a battery.
2. A battery. It powers every opening and the control board’s standby draw, day and night. See how long gate opener batteries last.
3. A solar panel. It puts back into the battery what the gate used, during daylight.
4. A charge controller. Often built into the operator’s board, it stops the panel overcharging the battery.

The panel doesn’t run the gate directly. The battery does. So the question is always the same: does the panel put back, on your shortest winter days, at least what the gate takes out?

How to size a solar setup in four steps

1. Daily energy for openings. Energy per cycle × cycles per day. Use your opener’s manual. If it lists motor current and travel time, energy per cycle is volts × amps × (2 × travel seconds) ÷ 3,600.
2. Daily energy for standby. Volts × standby current × 24 hours. This is the part most people forget.
3. Panel. Daily energy ÷ (winter peak sun hours × 0.86). The 0.86 allows for 14% system losses, the default NLR’s PVWatts uses.
4. Battery. Daily energy × the days you want to ride through without sun, divided by 0.5 so a lead-acid battery never goes below half charge. Trojan Battery recommends discharging to 20–50% of rated capacity.

Our solar gate opener calculator does all four with peak sun hours for your state from NLR (formerly NREL) data.

Worked example: the same gate in two states

A light home swing gate, 10 openings a day, 12 V system. We use a typical figure of 1.68 Wh per cycle, worked out from Mighty Mule’s statement that a full 12 V, 7 Ah battery gives about 50 cycles. Standby is 5.7 mA, the control board and remotes in LiftMaster’s published table.

	Arizona (Phoenix)	Connecticut (Hartford)
Worst-month peak sun hours (NLR)	5.53 h	3.22 h
Daily use: 10 cycles + standby	18.4 Wh	18.4 Wh
Minimum panel	3.9 W	6.7 W
Next common panel size	5 W	10 W
Battery for 3 sunless days (12 V)	10 Ah	10 Ah

The battery is the same because the daily use is the same. The panel nearly doubles in Connecticut because winter sun is so much weaker. Treat 1.68 Wh as a rough average: efficient openers use less, and heavy gates use more. LiftMaster’s chart, for example, shows some of its operators doing far more cycles on a 10 W panel than this example suggests. If your opener’s maker publishes a solar chart, use it.

Standby draw: the hidden load

A control board waiting for a remote draws current all day. So does every plugged-in accessory. LiftMaster publishes the standby current of its solar boards and accessories:

Item (LiftMaster figures)	12 V boards	24 V boards
Main board with remotes learned	5.7 mA	3.7 mA
Each plug-in loop detector	+6.6 mA	+3.8 mA
Wi-Fi/app module or wireless dual-gate link	+3.9 mA	+2.4 mA
Expansion board	+18.5 mA	+11.1 mA
Monitored wireless edge kit	+11 mA	+5.8 mA

An expansion board and two loop detectors add about 32 mA on a 12 V board. That is 9.1 Wh a day, more than five openings in our example. LiftMaster notes the expansion board can be unplugged if you don’t use its features. Battery-powered wireless keypads draw nothing from the gate battery.

Winter and cold

LiftMaster’s solar guide gives specific advice for cold climates:

• Cold batteries. Where it stays below 32 °F for more than two weeks, replace the standard 7 Ah batteries with 33 Ah batteries.
• Extreme cold. Below −4 °F for more than two weeks, daily cycles and standby time drop by at least 50%.
• Panel angle. In states that border Canada, tilt the panel an extra 15 degrees (60 degrees total) to catch low winter sun and shed snow.
• Snow. Clear snow and ice from the panel and from the gate’s path.

Our calculator’s “cold winters” option doubles the battery to cover the 50% loss.

Where to put the panel

A panel in the wrong spot can lose most of its output, and no amount of math fixes that. Our solar panel setup guide covers mounting, angle and wiring step by step; the short version:

• Full sun all day. LiftMaster says the panel must sit in an open area, clear of trees, buildings and other shade for the whole day. A post shaded only in the afternoon still loses part of every day’s charge.
• Face south and tilt it. The sun-hour figures in our calculator assume a south-facing panel tilted at your latitude. Laying it flat or facing it east or west gives less in winter.
• Keep it clean. LiftMaster recommends cleaning the panel regularly. Dust, pollen and bird droppings all cut output.
• Weather. Snow, heavy fog and heavy rain reduce the charge, per LiftMaster. A steeper tilt in snowy areas helps snow slide off.
• Cable run. Keep the panel close to the operator. Low-voltage DC loses more over long wire runs; check the size with our wire size calculator.

Solar or run power?

Solar makes sense when power is far away and the gate is light and not too busy. Running power makes sense when the gate is heavy, busy, or close to a building.

• Distance. HomeWyse estimates trenching at about $11.55–$27.48 per foot in favorable soil, before wire, conduit and an electrician. At 500 ft that is roughly $5,800–$13,700. Our cost calculator adds it up for your run, and our gate opener cost guide explains each line.
• Weight and traffic. Heavy gates and frequent openings need more energy per day, so the panel and battery grow quickly.
• Wire size. If you do run power, long runs need thicker wire. Check it with our wire size calculator.

With power at the gate, see the best automatic gate openers, or our picks for swing and sliding gates. Still deciding? Our guide to choosing a gate opener walks through every check.

Choosing a solar gate opener kit: what to check

We don’t recommend specific solar kits because our partner doesn’t sell them. Whatever brand you look at, check:

• Rated gate length and weight, for your leaf, with margin for wind on solid gates. Not sure of the weight? Weigh your gate first.
• The maker’s solar chart: cycles per day by panel size, battery and region. LiftMaster publishes one by sunlight zone.
• Standby current of the board and every accessory you plan to add.
• Battery size and type, and whether a larger battery fits for cold climates.
• UL 325 listing and which entrapment sensors come in the kit.

Mighty Mule, for example, says all of its openers are 12 V DC units that run from a 7 Ah battery, which is why they’re common in solar setups.

Safety

• Solar openers move the gate with the same force as any other. UL 325 requires entrapment protection such as photo eyes or edge sensors (what UL 325 asks for).
• ASTM F2200 covers how automated gates are built, for any power source.
• Follow your opener’s manual for how the panel and any backup charger connect to the board.