Some technical questions

Some day, you will need a new 12 volt battery. Leaving the dome light on hastened that day, no one knows by how much.

I leave the A/C on all the time, I never 'start' the A/C separate from starting the car. (It is never NOT too hot for me in Mississippi)

There are some specific situations where a 1 minute warm up uses less gas than just driving away, but they are rare.

Regular unleaded 87 octane gas is ideal, Toyota warns against Premium and E85, preferring E10 or less. 85 Octane gas is OK in mountains.

 

A bad one. The scale of "the bad" is not calculable. Remember the Prius' aux battery is a normal world sized battery, not a normal USDM (United States Domestic Market) sized battery. This means it is not designed to power your radio, your headlights, and your CB radio while sitting with the car off for 4 hours in a parking lot. It is designed to maintain power to the systems that need it like keeping memory of DTC's, keeping a memory of engine performance, and small things like keep the time and your station presets on the radio. Treat it as such.

The dome light bulb is a DE3175 which is a 10W bulb. So if you left it on for an hour, you wasted 10 Watt-hours of power.

The small battery, "aux" or "auxiliary", has few purposes. The first is obviously to keep power with the car off. This is related to the design of the large battery, i.e. the traction battery. When the Prius is not READY, the traction battery is 100% completely and physically disconnected from the car. This is a safety reason and a lifetime reason. Safety means there is no physical path for high voltage DC power to get to the car's shell. In the case of an accident or malfunction, there is no danger to the occupants or rescue crew. The system is taken out of the equation. Lifetime is to protect exactly what you did with the dome light. If this drain happened to the traction battery, it lowers its life slightly. Now 1 hour of a dome light won't do any significant harm. But headlights on overnight would, or something to where the user drains it for some silly reason. It is easier and better to replace a $200 99% recyclable lead acid battery then a $2000 80%-90% recyclable battery. And if you did drain it, there is no way to charge it (there are ways, but no "average joe" way other than a costly dealership visit and a special charger flown in from Japan, seriously...) The battery spins the engine on starting, so no juice to spin the engine, no charge from the engine to charge the battery. Classic chicken and egg problem.

Once the car is READY, the aux battery is completely taken away from the picture other than being a parasitic load on the inverter to keep it charged and ready to be used next time. All power is derived from the HSD in some way through the inverter and back out to the systems. Regen or traction battery to the inverter makes a nice stable and clean 12v power rail (13.8v in reality I believe)

The AC is electric, has nothing to do with the gas engine.

A warm engine is a happy engine, that is true of all ICE vehicles (internal combustion engine). The Prius contains an ICE so it stands true. However the car does this for you. There is a "warmup" period built into the car's algorithms. Until the first time your engine shuts off after being READY'd, it is in warmup mode. In this mode it will try to take most power out of the traction battery (expensive in fuel economy) and use the engine little. It is also believed that the Prius runs the engine richer to warm it up even more quickly (again expensive in fuel economy). But the quicker the engine is warmed up the quicker the tailpipe emissions drop to their best values. Remember, that was the goal of the Prius design. Not to get the best fuel economy, but to minimize emissions. Getting great fuel economy is a welcome and now expected bonus.

Not only is it OK, it is required. Well not required, but really highly recommended. Putting in a higher octane gas does nothing but retard the timing and take longer to explode. You don't want this. The Prius will run on it, just like any well designed car that requires premium will run on regular. These well designed cars monitor the valve timings and adjust for silly user inputs like the wrong octane gas, or elevation changes.

My Prius runs exclusively on 85 octane (high elevation).

In the GenIII forum, or whereever best suits your posts

and welcome!

 

That was the simple explanation on how this extremely complex car operates.

Either. If the car is not READY, it is always the aux battery. If the car is READY it is always the inverter. The inverter can then be powered from an MG in under the hood or the traction battery in the rear, or usually a combination.

Yes. And really 1 hour of a 10W bulb isn't going to do any noticeable damage. Parking outside on a really cold day will hurt the lead acid battery more than 10Wh of draw.

Yes

The Prius does this automatically and without severe hacking of the main Hybrid ECU, you cannot prevent it.

Because they are more than likely using belt driven AC units. This is not a hybrid versus "regular" car thing. It is an electric versus belt driven pump thing. Since the AC is electric, as long as there is power the AC will work. On a belt driven car, the engine needs to spin to drive the belt connected to the AC compressor. When the engine stops, the AC stops. Honda's hybrid system has a belt driven AC. So when at a traffic light and the engine shuts off because it is a hybrid, the AC also shuts off and blows warm air... How lovely.

Define cold. Your location says LA. You don't see cold... ever. If it is -30C out, you will want to plug in an engine heater and wait for it to warm up before putting strain on it.

And remember, the Prius does this for you already. In S1 (Stage 1, i.e. warmup) it runs the engine with little to no load and still moves the car mostly on electric power from the traction battery. In a normal car this can't be done since the engine is the only thing to moving the car. If you were to start a normal car and then have a few well trained monkeys push you around, you would be moving and the engine would be warming up with little to no load (you probably still want the radio on to drown out the monkey noises). This is the same in the Prius. It starts the engine, and it just sits there and gets hot wasting fuel while some other power source moves it. Instead of monkeys, it is a well designed electric propulsion system.