Two loads, and the small one is often bigger
A gate operator has exactly two power loads. It runs a motor for a few seconds at a time, and it sits there the rest of the day keeping a control board, a radio receiver and usually a keypad alive. Do the arithmetic and the second one keeps winning. A five amp motor running fifteen seconds each way uses about 0.042 amp-hours a cycle. Twenty cycles a day is 0.83 amp-hours. A hundred milliamps of standby is 2.4 amp-hours a day, all on its own, and it does not care whether anyone came home.
That ratio is the single most useful thing to know about a solar gate, because it tells you where to look when the battery keeps going flat. Adding a few cycles a day changes almost nothing. An accessory drawing more than its data sheet suggests, a loop detector left powered, or a camera sharing the battery changes everything. On a busy commercial entrance the balance flips and the motor dominates, but on a house it usually does not.
The worst month is the whole question
Solar gate installations fail in the same way every time. They go in during summer, work perfectly for months, and then stop being reliable in the middle of winter. Nothing broke. The panel is producing a third of what it produced in June, the battery is cold and delivering less than its nameplate, and the number of arrivals has not dropped at all.
So the figure to put in the peak sun hours field is the one for your worst month, for the way the panel is actually mounted, with whatever shades it. A panel bolted to a gate post is usually near vertical, aimed at whatever direction the post happened to face, and shaded by exactly the trees that line most gated driveways. It is not a roof array and it should not be given roof array numbers. Panel angle for a given latitude and season is on the tilt angle calculator, though on a gate post the mounting usually decides the angle for you.
| Where the amp-hours go | What moves it |
|---|---|
| Motor, per cycle | Gate weight, run time, how hard it drags. Fixed once installed. |
| Motor, per day | Cycle count. Rises with household size and deliveries. |
| Control board standby | The operator you chose. Not adjustable. |
| Accessories | Keypad, receiver, loop detector, camera. The one you can change. |
The busy day, and why it matters more than the average
Averages hide the case that actually strands you. A gate doing twenty cycles a day and a gate doing sixty on the one day a month you have people over draw the same average over the month, but the second one meets its worst day and its worst weather at some point, and that is the day the gate stops halfway. Entering a multiplier for a busy day gives you the shape of that, and comparing it against the usable battery gives the number of such days a full battery would carry.
None of that is a verdict. This page does not say a battery is big enough or a panel is big enough, because doing so honestly needs the battery datasheet, a temperature profile, the real irradiance at that spot and a depth of discharge decision that belongs to whoever owns the battery. What it gives is the daily arithmetic, and which half of it dominates.
Depth of discharge is a datasheet question
The share of the battery you can use is not a fixed number and it is not the same across chemistries. Lead-acid batteries lose cycle life quickly when taken deep, lithium tolerates far more, and both have datasheet curves that trade depth against how many cycles you get before the capacity falls off. The figure to enter is the one you have decided to accept for the battery you own, and the datasheet is the source. The battery runtime calculator goes into that in detail for a continuous load.
The part that matters more than any of this
A powered gate is a machine. It moves a heavy leaf under motor power across ground where children, pets and people on foot are, and the ways it injures and kills are well documented: a person or a limb caught between a closing leaf and a post, a child riding or climbing a leaf, a hand in the path of a rolling gate at a roller post. Which safety devices an installation requires, where they go, how the operator is set up and how any of it is tested belong to the operator manufacturer's instructions and the safety standard the operator is listed to, and to the installer who does the work. None of that is on this page and this page will not summarise it. If you are considering a powered gate, that conversation starts with a gate automation installer and the manufacturer's manual, before any of the arithmetic here matters.
Everything on this page is energy bookkeeping. It has no view on the operator, its installation, its safety devices, its force settings or anything else about how the gate behaves when something is in its way. If you are working out power for a gate you are planning, the installer conversation comes first and this comes second.
Questions people ask
How many amp-hours does one gate cycle use?
Motor current times run time, doubled for open and close. A five amp motor running fifteen seconds each way is 5 times 30 seconds, which is 150 amp-seconds, or about 0.042 amp-hours. That is genuinely small, which is why the standby draw usually matters more on a residential gate. Get the motor current from the operator data or a clamp meter rather than guessing it.
Why does my solar gate work all summer and fail in winter?
Three things move against you at once and none of them is the gate. The panel gets a fraction of the peak sun hours it got in June, often with a lower sun angle that a near-vertical post-mounted panel handles worse than a roof array does. The battery is cold and delivers less than its nameplate. And the number of arrivals is unchanged. Run the numbers with your worst-month sun hours and the picture usually explains itself.
Is standby draw really the bigger load?
On most houses, yes. A hundred milliamps around the clock is 2.4 amp-hours a day, which is more than twenty cycles of a typical residential operator. It is also the part you can sometimes do something about, because the control board draw is fixed by the operator you bought but the keypad, receiver, loop detector and camera hanging off the same battery are choices. Check each one against its data sheet.
Does this tell me what size battery and panel to buy?
No, deliberately. It gives the daily amp-hours in and out and how many days a battery would carry with no charge at all, which is the arithmetic. Turning that into a purchase needs the battery datasheet, a temperature derating, real irradiance data for your site and shading, and a depth of discharge decision. Those belong to you, the equipment datasheets and whoever installs it.
What about the surge when the motor starts?
It is real and it is not what fills the day. Starting current can be several times the running figure for a fraction of a second, which matters for whether the battery and wiring can supply it at all and for how the controller behaves, but it contributes almost nothing to the daily amp-hour total. This page is about the daily budget, so it uses the average running current. The instantaneous question is an equipment and installation matter.