re: AC management strategy when you go to work

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I bet you're one of those people (like most women) who thinks the lower you set the thermostat the faster it cools off the house.

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Driving an automobile has screwed them up in their thinking.

Driving 60 mph gets you somewhere twice as fast as would driving 30 mph.

They don’t realize that the A/C system has only one cooling rate.

They have minds like Swiss Cheese.

I shouldn't have said "sealing off" two rooms. Instead, I should have said reduce flow to the unused rooms.

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When you start closing registers, you aren’t magically making the system cool less space more efficiently.

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Except that's exactly what I did. But it wasn't magic. Like I said my energy bill went from $300 last July 2025 to $125 June 2026. But I'll admit most of that is due to raising the thermostat to 78 during the day while I'm at work. The main thing I noticed when closing the registers and closing the doors to those rooms is that my AC can keep up now on the weekends during the hottest part of the day. Before, my unit would run nonstop from about 11am-5pm and struggle to stay below 76. Now with those 2 rooms closed off with minimal air flow, my unit can keep up much better.

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conditioners are sized for the total conditioned square footage of the house—not for whatever rooms you decide

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So a system designed for 2000 SF definitely won't work for 1700 SF, Right? That 15% volume reduction is going make my system inoperable?

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The “less volume to cool” argument also ignores how thermostats work. When you create large temperature imbalances throughout the house, it will likely take longer for your thermostat to reach its set point due to heat coming through the walls from the closed off rooms

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I don't think you're going to get much "heat coming through the walls" on a 10° differential. My house is at 72° and the unused rooms are 82°. That 10° difference isn't going to transfer through two layers of sheetrock enough to make a difference.

You must be an engineer. I see this a lot in my line of work where young engineers with a lot of theoretical knowledge don't realize that their theories oftentimes don't work well in practice in the real world.

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Adjustable registers are there to fine tune airflow not cut it off.

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This we can agree on. As previously stated, I shouldn't have said "sealed off" the rooms but rather fine tune it to minimize air flow to those unused rooms while increasing or maximizing air flow to the master bedroom.

You are mis-informed. The system is designed for some air flow to each room. Don't shut off rooms.

I leave mine on 73 during the day and 70 when I go to bed.