Your car isn’t really “asleep” when you lock it, and that fact shows up in the way electric‑vehicle batteries lose a little charge even while the vehicle sits idle. Leaving an EV at the airport for a week can already cost you a few percent of range, and the loss can be noticeable even if the odometer hasn’t moved.
The drop in charge is real, but how much you lose depends on the model and what the car is doing while you’re away. All lithium‑ion cells naturally lose a small amount of energy through electrolyte oxidation and reduction, a process called self‑discharge. That loss is tiny compared with the energy used for driving. The bigger culprit is the suite of systems that stay active after you lock the doors.
A locked EV does not shut down every electrical component. The battery‑management system still checks battery health at intervals, and the high‑voltage pack often recharges the low‑voltage 12‑volt battery that powers locks, computers and other electronics. Tesla notes that its Model 3 performs these checks and any needed maintenance while parked, and Rivian confirms that its R1T also draws from the high‑voltage pack to keep its 12‑volt system topped up.
Connected services add another layer of consumption. Through a smartphone app you can see the car’s status, start climate control or pre‑condition the cabin before you get in. Tesla lists app requests, climate functions and infotainment as sources of power draw when the car is stationary. Third‑party apps that repeatedly wake a sleeping vehicle can increase the drain. If you leave cabin cooling on during hot weather, the system will use energy just like it would while you’re driving.
Cold weather makes the situation more complex. Battery temperature swings can cause the range estimate to shift even though the car hasn’t used any extra electricity. Model 3 owners can check the Energy app’s Park tab to see the actual energy used while the car is parked, which is more informative than watching the range figure fluctuate.
Optional features can be the biggest drain. Tesla’s Sentry Mode runs cameras and sensors to watch for suspicious activity, and Rivian’s Gear Guard Motion Cam does something similar. These security eyes are useful in an unfamiliar lot, but they do consume power.
How much charge can you expect to lose? Tesla’s Model 3 manual states that the battery may lose about one percent per day, depending on settings and conditions. Some owners report a loss of just 0.1 to 0.3 percent a day when the car is truly sleeping, while models running energy‑intensive features can lose several percent each day. The size of the battery matters, too: a 0.5 kWh loss is roughly 1.2 percent of a 42 kWh pack but only 0.6 percent of an 80 kWh pack, making the same drain more noticeable on smaller city EVs.
If you plan to leave your car for an extended period, turn off unnecessary surveillance and climate controls, limit apps that repeatedly wake the vehicle, and make sure you have enough charge to get moving again. Tesla actually recommends keeping a Model 3 plugged in when it’s not in use for several weeks and maintaining around a 50 percent state of charge for long‑term storage.