Looks like someone tried to lever my front nearside window down

[stopcrazypp]

There's no such thing as "shore power" in a Tesla.
The only way AC power gets into the car is via the charger. The charger that can do 11kW. There is zero way sentry draws 11kW. Or even 1kW.

The HV battery system in the car is pretty simple. It's one bus. On that bus is the battery, the battery charger, and the loads. Nothing "flows through" the battery. If the voltage on the bus is higher than the current battery SoC, the battery charges. If it's lower, it discharges. The only thing on this bus that can balance this out is the charger.

Sentry runs off the 12V system, and uses something around 100w.
This can easily be run for 30 minutes off just the 12V battery. But to run it for any real length of time, that 12V system needs to be maintained with external power. This is where the HV battery comes in. The PCS (power conversion system, DC/DC converter) is left on when in sentry to keep the 12V system maintained and not drain the 12V battery.
By definition, the PCS cannot be on unless the contactors are closed. This is just the architecture of the power system. These contactors and the PCS being on add another 100w or so as they are not 100% efficient.

So now your HV battery is being drained at 200+W. Which is nothing for it, except this is 24/7, so that's 4.8kWh per day, which is about 20 miles of rated range.

So now let's ask how we'd handle this off "shore power" which is actually the battery charger. The one designed to max at 11,000w. And we need it to accuratley output about 200w. If it does more, the battery charges. If it does less, the battery discharges. A charger that wasn't really designed to do less than 1kW, as the lowest normal input it takes is 12A @ 120V.

And that battery charger itself is not 100% efficient, so just having it running at all the time wastes a lot of electricity. Which is why when you charge at 120V, you lose about 30% of that energy, but when you charge at 6kW you hardly notice it.

So it makes a lot more sense to let the battery discharge 1-2%, then turn on the charger at full rate and top it off, then wait until it discharges some and then repeat. But this does put cycles on the battery.

This all makes sense when you realize that Sentry is a marketing gimmick afterthought, not part of the car's original requirements.

To clarify, I don't mean Sentry exceeds the AC power (termed as "shore power" in this case), I mean presumably it is powered via AC also when car is awake. This means as it relates to the comment, it doesn't cycle the battery in this case when it is plugged in.

Sure, it may be very inefficient, but people may not be overly concerned about that vs battery wear.

For myself I find the inefficiency way too high for long use, so I don't use Sentry unless I'm shopping and not parked very long. For longer term parking I use a separate recording system that uses a small fraction of the power.