Using Solar to Keep an Aircon Going During Brownouts: What's Realistic

Solar can keep one efficient aircon going through a typical brownout, but only for a few hours and only with a large power station. A realistic setup is an EcoFlow DELTA 3 Max (2,048 Wh) running a low-watt 1HP inverter unit like the TCL TAC-11CSD/P7 for about 4 hours, with EcoFlow 220W panels topping it up if the outage hits in daytime. Whole-house cooling isn’t realistic with portable gear.

What’s realistic and what isn’t

The maths for a 4-hour brownout

Example assumptions: 4 hours, and the unit averages half its rated watts once the room is cool. That’s the DOE’s older label factor for inverter units, and a hot afternoon will push it higher. The 0.85 is our runtime calculator’s usable-energy figure for AC devices.

For brownouts longer than about 4 hours, or on hot afternoons, the DELTA Pro 3 is the safer size. Both stations have ample AC output: 2,400W for the DELTA 3 Max and 4,000W for the DELTA Pro 3.

Daytime brownouts: let the sun help

If the outage is during the day, portable panels keep feeding the station:

• DELTA 3 Max: 2 × EcoFlow 220W in series, 440W usable (MC4 leads joined; MC4-to-XT60i cable included with the panel). The station takes a maximum of 500W of solar.
• DELTA Pro 3: up to 6 × 220W in series on the High-PV input (1,320W usable). EcoFlow’s manual specifies a “Solar to XT60 Charging cable” for that port.

In strong sun, 440W covers a good part of a 650W unit’s example 325W average draw. Clouds and the rainy season cut that sharply. Portable panels can be set up by the owner following the manual.

Connecting the aircon safely

• Window units with a plug: plug straight into the station’s AC outlet.
• Split units on a dedicated circuit, or hard-wired units: don’t improvise. Any connection between a station or inverter and house wiring needs a licensed electrician and an LGU permit. Never feed power back into house wiring through an outlet.
• Auto switchover: EcoFlow lists a 10 ms UPS switchover for both the DELTA 3 Max and the DELTA Pro 3 when the load is plugged into the station and the station into the wall.

Make the battery last

• Cool one small room with the door shut and curtains closed.
• Set 24°C, as the DOE recommends.
• Pre-cool before a scheduled brownout while grid power is still on.
• Recharge from the wall as soon as power returns.

What to buy

• EcoFlow DELTA 3 Max: Shopee · Lazada
• EcoFlow DELTA Pro 3 for longer brownouts: Lazada (EcoFlow PH) · Shopee
• Panels: 2–6 × EcoFlow 220W on Lazada
• Plug-in inverter window unit: Kolin KA-100GQAIINV32 on Lazada, or TCL TAC-09CWI/UJE2 on Lazada · Shopee
• Lowest-watt split unit: TCL TAC-11CSD/P7 on Lazada · Shopee (installed by a licensed technician)

Check today’s price before you buy.

Bottom line

Expect one efficient aircon, one room and a few hours. A DELTA 3 Max handles a short brownout with a 650W unit, and a DELTA Pro 3 handles longer ones. Solar helps by day but not at night. For wider brownout planning, see our backup power guide.