AC during a heat wave

[Jerry1]

It's our turn for the heat wave of the summer (Michigan). I'm wondering what people do when it comes to setting their thermostat. Do you let your house get a little, or a lot, hotter than you would on average? One thought I have is that I should back off during the hottest part of the day in order to do my part to tax the grid less during such times. Another concern is that at some point, my AC would pretty much run continuously if I was to keep it where I like it - 74°. At this point, my thought is to cool off the house in the morning and then let it drift up to 80°. Then, cool it back down in the evening so it's comfortable for sleeping. Anyone else manage the AC differently during the high heat or do you just run the AC at your preferred setting?

 

[pb4uski]

No AC at our Vermont summer home and typical of many homes here, though mini-split installations are becoming increasingly popular.

We face east. What we have found works best when it is hot is to leave some windows open at night to cool the house then in the morning close everything and pull blinds on east facing windows to reduce direct sunlight into the house. As the day progresses we can open blinds on the east side and close them on the west side.

Plus a big fan in the great room and one in the master bedroom.

Also, it is much cooler downstairs which is below grade to the west and walkouts to the east.

 

[GenXguy]

I'm only running AC in my living room during the day using an inverter AC unit, which cools the kitchen some as well, and my target for cooling is normally right around 80 degrees, even if it's not a heat wave. At night, I'm using the new bedroom AC unit, also an inverter AC, and I might cool down to 76 to 78 degrees in the bedroom. Again, not changing because of the heat wave. I'm already using much less AC power than most people. I do have central air, but it's over 25 years old, and I'm not using it much at all beginning last year when I first installed a window AC unit.

 

[Flyfish1]

My wife will not allow heat to drift up above 74 degrees...ever. So, I set it and forget it. 73 or 73 degree settings and walk away and yes this week it is running almost non stop. Same in the winter it's a programmed 67 or 68 degrees in the daytime and 63 in the bedroom at night. I gave up trying to pinch pennies on that and hear the complaints from my lovely wife.

 

[disneysteve]

74? I'd be melting and the wall paper would be peeling off from the humidity.

Our AC is set at 70° 24/7.

What do we do in a heat wave, as the one set to start tomorrow with temps getting into triple digits? We keep the shades and blinds closed that would normally be open. That helps a tiny bit. Other than that, we just go on with our lives. And I brace myself for the $500+ electric bill that will come next month.

 

[audreyh1]

We keep the house at 78 during the day and 77 at night during the summer. Fall and spring, cool to 77. We barely have a winter, but we do set a heat threshold.

Our electric bills are modest. Often below $100, occasionally above $115 to $145 maybe.

 

[RetiredHappy]

We run both thermostats at 78 during the day, and the one that controls the bedroom, we run it at 73 degrees F starting at 8:30pm until 6am from March/April until November. When it starts to get cold, we run heat at 76 during the day and 71 during the night.

 

[isisdave]

The house stays set to 78. We spend most of our time in a sunroom that has a PTAC (motel-style) unit down low in one corner, and there's an overhead fan, so the temperature through the room varies, although it's usually at 74.

The bedroom, however, has its own window unit which DW sets to Igloo (66) during sleep hours.

 

[rk911]

This week the Chicago area is expecting daytime highs in the mid to upper 90's with heat indexes in the low triple-digits. We've set the AC to 76/77 (daytime) and 77/78 at night. During this heat we run it 24/7 but the bedrooms, main level front room and sun room all have ceiling fans. Other rooms have floor fans. The sun room has its own mini-split set to 80.

 

[Koolau]

Our AC is set at either 78 or 79. 80 is just a bit warm. At night, without sun load, the AC doesn't run too much and it doesn't run much til about mid-day. Then it struggles to keep up until dark. I think that's supposed to be ideal. Moisture is constantly removed and cool-clammy air is never an issue.

Full disclosure, we also use a ceiling fan. The dry, conditioned air blowing gently on us makes it very comfortable even on hot days. YMMV

 

[Mr. Tightwad]

Never turned on AC in my life in a home of mine.

I have turned it on in other peoples home at their request.

This house has 2 units, both non functioning when I purchased the home 28 years ago.

 

[Jerry1]

Never turned on AC in my life in a home of mine.

I have turned it on in other peoples home at their request.

This house has 2 units, both non functioning when I purchased the home 28 years ago.

I'm guessing you don't live in an area with high humidity. One of the main benefits I get from running the AC is that it reduces the humidity.

 

[Koolau]

Never turned on AC in my life in a home of mine.

I have turned it on in other peoples home at their request.

This house has 2 units, both non functioning when I purchased the home 28 years ago.

Yeah, we don't have AC in the Islands. Our condo is ideally situated so that the Trades blow through almost all the time. A few people in our building have set up those "standing units" that have a large duct that fits through a window. We've never felt the need though once in a great while, AC would be nice. Mostly, we just turn on a fan/overhead fan.

 

[38Chevy454]

In the spirit of E-R: BTD and keep temp same as any other summer day 74 set point.

 

[Mr. Tightwad]

I'm guessing you don't live in an area with high humidity. One of the main benefits I get from running the AC is that it reduces the humidity.

Southern California. Humidity a non factor all year except around August/September where a slight bit is present, but nothing compared to most of the country.

 

[Montecfo]

We set the thermostat higher than a lot of folks. But we do.not raise it in hotter weather. That would be counter productive.

But a heat wave here is temps in n 90s for a few days.

 

[Koolau]

In the spirit of E-R: BTD and keep temp same as any other summer day 74 set point.

Do you then cover up to sleep? We notice in the Islands that we're chilly if the temp drops into the low 70s at night (with the Trades blowing). Then I add a blanket to the flannel sheet I usually use. I'm sure there is some acclimatization and we have a very narrow range of comfort - usually upper 70s to low 80s is what we like.

 

[USGrant1962]

We set the thermostat higher than a lot of folks. But we do.not raise it in hotter weather. That would be counter productive.

But a heat wave here is temps in n 90s for a few days.

Hmm. You might want to look at the forecast for Thursday through the weekend. Highs at 100+ for the whole region.

 

[audreyh1]

This is actually pretty moderate for us this time of year:

Also plenty of wind which certainly helps.

Texas would not have nearly such a large population if it weren’t for A/C.

 

[Turbo29]

Mine is set at 77°F from 5am until 12:30pm, 74°F from 12:30 until 3pm, 82°F from 3-6pm (peak rate for power), 77°F from 6pm until bedtime and then 72°F until 5am the next day.

On the weekend when there is no peak rate its 77°F until noon, 78°F until 6pm, 77°F until bedtime and then 72°F overnight.

Edit to specifically address the "heat wave" part of the question: The whole summer here in Arizona is a heat wave.

 

[Montecfo]

Hmm. You might want to look at the forecast for Thursday through the weekend. Highs at 100+ for the whole region.

I see a lot of rain and nothing above the 90s and just for a few days.

My electric bills have not been over $100 either so far but maybe it is coming.

 

[NW-Bound]

We hit 111F high last week. The low of the night was 92F, right before sunrise.

I set the thermostat at 80F, and as cool air sinks, it is about 78F or lower at ground level. This is quite comfortable, because the humidity is so low. The dew point is often below 32F. At the crest of the vaulted ceiling, the temperature is 85F or so.

The ground floor is cooled by 3 minisplits, totaling 3 tons. The central AC of 5 tons is turned off, and the 5 rooms upstairs are abandoned to the heat.

Back before I installed the minisplits and the DIY solar system, I ran the central AC to cool both stories of the house. It was undersized, and ran non-stop 24/7, and still struggled to keep the interior at 80F. Power consumption was as high as 100 kWh/day.

Now, the solar panels provide 50-60 kWh/day, and that's almost enough to feed the 3 mini splits for the 1st floor. When the high temperature is in the low 100F, I have enough solar juice stored in the lithium bank to last through the night. When it got about 110F like last week, the solar system ran a deficit, and it had to pull in 20-30 kWh from the grid to help.

 

[Route246]

In our current home I just set it to 72. In the home we are remodeling it will be all electric except for gas range cooktop where my wife insists on gas. It is a remodel so we don't need to have electric whereas new construction requires electric. PG&E rates are the highest in the country exceeding $0.45/kWh and they just approved another rate increase. I'm sizing the solar now and we are at about 60-70kWh/day with gas dryer, water heater and heating. These will all go to heat pump or electric, the house is about 1.8x bigger but the insulation will be state-of-the-art spray foam with standing seam metal roof which I'm told is also a great reflector. Currently looking at 20kW solar with 4 Franklin aPower batteries. The goal is to be off grid as much as possible and with NEM3 feed as little as possible back to the grid. We have two Plug-In EV and 2 ICE vehicles. During the dark winter months we can cut back on EV charging if necessary but I'm hoping to have excess in the summer so that during the dark winter times we have sufficient generation to avoid drawing expensive PG&E power. We will also have backup Generac generator power available.

That said, I told my wife I hope to have the thermostat set to the same temperature all year regardless of the temperature outside. I told her I want it like the library, the doctor's office or other commercial space where the temperature is set the same regardless of what it is outside.

Once final inspection is complete I plan to have minisplits added to both garages and my man cave. This has to be done after inspection due to property tax assessments. If it has HVAC it gets counted in livable floor space and the property tax becomes insane.

If we run out of generation in the winter we can turn off heat in zones we are not using.

 

[Sunset]

We have ours set at 75 in the day when we are at home. If we go out for hours I'll raise it to 78 .
At night we lower it to 73.

Our central air seems to fail during heat waves, it's been the condenser two times. I have a spare now, but still hate changing it when the temp is 95 F.

 

[Texas Proud]

As pointed out by others... we always have a heat wave down here... and always run the AC the same..

Now, DW is a little strange... if it is summer she is hot at 74 ish but cold in the winter at the same temp...