How to make a window air conditioner smart

Look at your controls first

Window units fall into two types, and the type decides what works.

• Mechanical controls. Rotary knobs and a slider, no remote, no display. They usually have no IR receiver, so an IR controller will not work. When power returns, they often start again at the same setting, so a smart plug can work.
• Electronic controls. A digital display and a remote. An IR controller works. Many electronic units do not restart after power loss: they wait in standby until you press a button, so a smart plug will cut the power but not turn it back on.

Test this before you buy anything: set the unit to cool, unplug it, wait ten seconds and plug it back in. If it comes back on at the same setting, a smart plug can work. If it sits idle, use IR or choose a unit with Wi-Fi.

Route 1: a Wi-Fi IR controller

A small Wi-Fi device with an infrared emitter learns or looks up your remote’s codes and sends them on your command. Place it where it can see the unit’s IR window, within a few feet and with a clear line of sight. It adds schedules, geofencing (cool the room as you drive home), voice control and, with a built-in sensor, a temperature reading in the app.

Limits to understand: IR is one-way. The controller cannot know the unit’s real state, so if someone uses the remote, the app can be wrong. Not every feature is available in every code set, such as sleep or eco modes. The controller’s sensor measures the air where it sits, not at the unit.

Route 2: a smart plug

Only for units that restart on power-up. The Department of Energy says smaller units (less than 7.5 amps) can plug into any 15- or 20-amp, 120-volt household circuit that is not shared with major appliances, and larger units need a dedicated 115-volt circuit; the largest need 240 volts. That matters here. Use a heavy-duty plug rated for at least 15 A and 1,800 W, read the unit’s amp rating on its label and make sure it is on a circuit with room to spare. Never use an extension cord or power strip with an air conditioner; check the manual.

The biggest risk is the compressor. If power is cut while the compressor is running and then restored right away, the compressor tries to start against high pressure. Most manuals say to wait a few minutes before restarting. Program a minimum off-time of several minutes and avoid automations that toggle the plug repeatedly. Check the manual for the exact wait. Measuring draw with an energy-monitoring plug helps; see smart plugs with energy monitoring.

Route 3: a unit with Wi-Fi built in

ENERGY STAR says most of its U-shaped room air conditioners and many other certified models are smart and have connected functionality: remote control, scheduled temperature changes and energy-use feedback, and they can be “smart-grid ready” for programs some local utilities offer. If you are replacing the unit anyway, this is the most reliable route, because the app talks to the unit directly.

Check which assistants it supports (Alexa, Google Home, Apple Home), and whether the maker states how long it will support the app. Secure the account as the FTC advises: a unique password, two-factor authentication and software updates.

Size and cost: the numbers to know

ENERGY STAR’s sizing chart runs from 5,000 Btu/h for a 100 sq ft room to 34,000 Btu/h for 2,500 sq ft, and the DOE says you typically need 20 Btu per sq ft. An oversized unit costs more, wastes energy and does not dehumidify as well, so do not buy bigger to be safe.

Efficiency is measured by the energy efficiency ratio (EER): Btu per hour divided by watts. An 8,000 Btu/h unit at an EER of 11 draws about 727 W. Running 8 hours a day at 18¢ per kWh costs about $1.05 a day. Try your own numbers in the device energy cost calculator.

Automations that actually help

• Cool before you arrive. Use geofencing or a schedule, ten to thirty minutes ahead.
• Off when a window opens. A contact sensor on a nearby window cuts waste. See door and window sensor automations.
• Fan first. Use a ceiling fan so you can set the thermostat higher.
• Time-of-use schedules. See time-of-use rates and your smart home.

Renters: a window AC is movable and no wiring is involved, but check your lease and building rules about window units before you install one.