Smart Thermostat Settings to Change During a Heat Advisory

A heat advisory is the wrong time to treat a Nest or ecobee like a generic wall thermostat. The familiar 78°F advice is useful context, but the live problem is usually buried one menu deeper: Eco Temperatures that are too loose, Away behavior that waits too long or guesses wrong, utility-event settings that nudge the setpoint, and comfort features that were designed for normal summer days. The old federal 75–78°F and 78/82/85-style guidance now has to be treated through secondary reporting because the relevant DOE page is no longer live, so don’t use it as the whole answer during an active advisory.[1][2]

Change these settings first

If someone in the home needs a lower setpoint for age, sleep, humidity, medical risk, medication, or basic safety, use the lower setpoint. The settings below are not a contest to endure the highest number on the screen.

Nest: make Eco recoverable before you worry about clever features

On Nest, start with Eco Temperatures. Not Sunblock, not Airwave, not the graph that tells you yesterday was efficient. Eco is the setting that can let the house drift farthest from comfort while still looking like the thermostat is behaving exactly as designed.

Google documents Nest cooling Eco Temperatures as a selectable range from 76°F to 90°F.[3] That range makes sense as a product setting because homes, climates, and occupancy patterns vary. During a heat advisory, the top end of that range is not a casual choice. If the thermostat lets the house climb into the mid-80s or higher while the attic is cooking, the AC may spend the rest of the afternoon running without making the rooms feel normal again.

Eco Temperatures

For the advisory window, set the cooling Eco Temperature to a number you can recover from, not the highest number that looks good in an energy report. In many homes, that means keeping Eco close enough to the occupied cooling target that the AC is not asked to claw back a huge gap at 4 p.m. If your normal cooling hold is 76–78°F, an Eco cooling point near the upper 70s or low 80s is a very different risk than an Eco point near 88–90°F.

The practical test is simple: if someone comes home during the hottest hour, can the system bring the main living area back to a safe, tolerable temperature before evening? If the answer is no, the Eco number is too aggressive for today. That is not a moral failure. It is a capacity and timing problem.

Auto-Eco and presence sensing

Nest can use presence behavior to switch into Eco automatically, and Google says it can take up to two hours for the thermostat to switch to Eco after everyone leaves.[3] That delay is usually discussed as an energy-saving limitation, but during a heat advisory the bigger concern is control. You do not want the thermostat making a comfort decision based on partial presence evidence while someone is napping, working in a room with poor motion detection, or arriving home before the peak heat is over.

If the house is occupied, has pets, or has anyone heat-sensitive inside, turn off automatic Eco behavior for the advisory or set an explicit cooling hold that overrides it. If the house will be empty all day, you can still use Eco, but choose a cooling temperature that does not turn the home into a storage battery for heat.

Sunblock

Sunblock is one of the rare smart-thermostat features that is easy to respect because the failure mode is so physical. If afternoon sun hits the thermostat, the thermostat is not just reading the room; it is reading the room plus a warmed-up device face. Google’s current support page describes Sunblock as direct-sun compensation for Nest thermostats.[4]

During a heat advisory, enable Sunblock if your Nest gets direct sun. Then sanity-check the result. Put a separate thermometer in the occupied part of the room, away from the window and supply vent. If Nest says 78°F but the seating area is drifting warmer, do not argue with the app; use the temperature where people actually are.

Airwave

Airwave is not a bad feature. It is a dry-house coasting feature. Google says Airwave can turn off the compressor and run the fan for 5–10 minutes, using remaining cold in the system, and that it only turns on when indoor humidity is low.[5] In a dry, shaded house, that can be a reasonable way to squeeze a little more cooling from a cycle.

The heat-advisory test is whether the rooms keep getting warmer after the compressor shuts off. If the fan-only tail feels like it is blowing lukewarm air through a sticky house, turn Airwave off until the advisory passes. This is especially worth checking if the thermostat is in a hallway that cools faster than bedrooms, an upstairs room, or a sun-exposed living area.

Cool to Dry

If your Nest menu includes Cool to Dry, treat it as a humidity decision, not as your heat-advisory cooling plan. Humidity control can improve comfort, but it can also change runtime in ways that are easy to miss when you are focused only on the temperature number. If the house feels hot because the indoor humidity is high, use a humidity-specific plan rather than blindly dropping the setpoint over and over; the site’s heat-index thermostat recipe goes deeper on that split.

ecobee: audit eco+ before the utility event audits you

On ecobee, the thing to inspect first is eco+. The name sounds like one feature, but ecobee presents it as a software suite that can include energy-saving automation such as Community Energy Savings, time-of-use behavior, and comfort adjustments.[6] That bundling is convenient in April. In an August heat advisory, it can make it harder to know which feature moved the target temperature.

eco+ and Community Energy Savings

Open eco+ and look specifically for utility-connected or peak-demand behavior. ecobee describes Community Energy Savings as a way for participating utilities and customers to reduce demand through eco+.[6] That may be perfectly acceptable on a normal peak day. During an active heat advisory, you should decide deliberately whether the house can tolerate the adjustment.

This is where vendor language and living-room reality separate. A small temperature change can be reasonable if the home was pre-cooled and the occupants are healthy. The same change can be a problem in an upstairs bedroom, a humid house, or a home with an older person who is already warm. If you participate in a demand-response program, know how to opt out before the event starts; for a fuller enrollment and opt-out audit, use the demand-response heat-wave guide.

Smart Home & Away

Smart Home & Away is useful when the thermostat’s idea of occupancy matches the house. A heat advisory is when mismatches matter. If someone is working quietly in a back room, sleeping during the day, or staying mostly outside the room with the thermostat, do not let occupancy automation decide that the home can float warmer.

For the advisory, use a manual hold or disable the occupancy feature that is most likely to misread the day. If you use ecobee room sensors, make sure the sensor participation matches where people actually are during the hottest hours. A living-room sensor is not protecting a west-facing bedroom if the thermostat is averaging it out of the decision.

Smart Recovery

ecobee describes Smart Recovery as a feature that learns how long the home takes to reach the next scheduled temperature and starts heating or cooling early so the target is reached by the scheduled time.[7] That can be exactly what you want if the schedule is designed around the heat. It is less helpful if the schedule was built for an ordinary workday and now the AC is trying to recover late in the afternoon.

Do not turn Smart Recovery into a substitute for a real pre-cooling plan. If you want the home cooler before a 4–7 p.m. peak, schedule or hold that lower target before the peak begins. Let Smart Recovery help execute the plan; do not make it guess the plan from a stale schedule.

Hold duration

The most ordinary ecobee setting may be the one that saves the afternoon: hold duration. A hold that ends at the next scheduled activity can expire before the hottest part of the day. A hold that lasts “until you change it” can protect comfort, but it can also waste energy overnight if nobody cancels it.

During a heat advisory, set a deliberate hold through the actual risk window: for example, through the late afternoon and early evening if that is when your home peaks. Then set a reminder to release it after the house and outdoor temperature have stabilized. The point is not to abandon automation forever; it is to stop a routine schedule from interrupting an emergency-day plan.

Pre-cool before the house is losing the fight

Pre-cooling is not magic, and it is not permission to turn the house into a refrigerator. It is timing. You ask the AC to do more work before the attic, walls, windows, and outdoor unit are under their worst load. Then, during the hottest or most expensive window, you let the thermostat rise modestly instead of forcing the system to sprint uphill.

APS frames pre-cooling around shifting cooling earlier before on-peak hours.[8] AEP Ohio describes demand-response events where participating thermostats may pre-cool before an event and then adjust setpoints by no more than 3°F during the event.[9] Those examples should not be read as a promise of savings in your home. They do show the basic heat-wave logic: lower the load before the grid and the house are both stressed.

• Before peak heat: use a lower but reasonable cooling target while the AC can still make progress.
• During peak heat: allow a small rise only if the house remains safe and comfortable.
• After peak heat: release the temporary hold or return to the normal schedule once the home has stabilized.
• All day: avoid deep setbacks that require a long recovery during the hottest outdoor conditions.

The savings math should stay in its lane. Consumer Reports describes a common rule of thumb that raising the thermostat by 1°F can reduce cooling costs by about 3%, while SMUD frames savings as 5–10% for a 2°F increase and recommends raising the thermostat between 5 p.m. and 8 p.m.[10][11] Those are heuristics and utility-program framings, not guarantees for a heat-soaked house with west windows and an undersized return.

If you want a more detailed timing recipe, especially for brutal afternoon peaks, use the site’s worked pre-cooling guide. If the question is less “what time should I pre-cool?” and more “why did this smart feature betray me?”, the broader smart-thermostat backfire analysis covers the feature-by-feature mechanics.

The 78°F baseline is context, not a command

The 78°F number survives because it is a useful reference point. It is high enough to reduce cooling load compared with lower setpoints, and it gives homeowners a shared starting line. But a heat advisory is not a lab condition. A thermostat reading 78°F in a hallway can coexist with an 82°F bedroom, high humidity, radiant heat from windows, or an occupant who is medically vulnerable.

USA Today reported World Health Organization guidance around 76°F in the context of heat-wave safety, alongside the broader health risks of extreme heat.[12] That is a useful reminder: comfort and safety are not luxuries layered on top of energy savings. If the safe number for your home is lower than the energy-saving number, the safe number wins.

Heat-advisory checklist

• Confirm the thermostat is actually in Cool mode, not Auto mode with a wide deadband or an old seasonal schedule.
• Set an occupied cooling target the house can maintain safely during the advisory.
• Nest: check Eco Temperatures first, then Auto-Eco, Sunblock, Airwave, and Cool to Dry.
• ecobee: check eco+, Community Energy Savings, Smart Home & Away, Smart Recovery, and hold duration.
• Use a temporary hold that lasts through the hottest window; do not let it expire at the next schedule change.
• Pre-cool before the hottest or on-peak period, then allow only a modest rise if the home remains safe.
• Avoid large daytime setbacks that the AC cannot recover from until late evening.
• Audit utility-event and demand-response settings before the event starts, not after the rooms are warm.
• Use a lower setpoint when health, sleep, humidity, age, or medical risk requires it.

Nest and ecobee can help during extreme heat, but the safest heat-advisory setup is usually less automatic than the normal summer setup. Make the thermostat follow the day you are actually living through: a recoverable Eco range, a hold that survives peak heat, a pre-cool window that starts early enough to matter, and no quiet utility or Away adjustment that changes the cooling plan without you noticing.

References

1. DoE Deletes Webpage Instructing People To Lower Thermostat to 78 — Newsweek
2. Federal energy program suggests keeping thermostat set at 78 degrees — 82 while you sleep — FOX 5 NY
3. Learn about Eco Temperatures, Eco when away & how to change settings — Google Nest Help
4. Learn about Sunblock and how to change settings — Google Nest Help
5. Learn about Airwave and how to change settings — Google Nest Help
6. The world's most advanced smart thermostat software | eco+ — ecobee
7. Get the most out of your thermostat — ecobee
8. Precooling — APS
9. How demand response helps protect the grid during extreme temperatures — AEP Ohio Wire
10. Best Setting for Your Central Air Conditioning — Consumer Reports
11. Heating and Cooling — SMUD
12. Cost or comfort? What is the best AC temp during the heat wave — USA Today — June 30, 2026