Solar Aircon at Night: Why You Need Batteries

Solar panels make no power at night, so a “solar aircon” at night is really running on a battery that the sun charged during the day. To cool a bedroom overnight, you need a battery big enough for the whole night and a solar array big enough to refill it the next day. A verified fit for a 1HP inverter unit is an EcoFlow DELTA Pro 3 with about 1,700W of EcoFlow panels.

The day-night cycle

Think of it as a loop that has to balance every 24 hours:

1. Daytime: panels charge the battery (and power anything running).
2. Evening and night: no sun. The battery alone runs the aircon.
3. Next morning: the battery is low, and the sun has to refill it before evening.

If a day’s solar doesn’t replace what the night used, the battery starts each evening a little emptier. In rainy season or typhoon weather, that happens fast. See charging on cloudy days.

How much the night uses

Example assumptions: a Kolin KA-100GQAIINV32 (1HP window inverter, 740W rated on its DOE label), running 8 hours overnight. It averages half its rated power once the room is cool, which matches the 0.5 factor the DOE’s older label formula uses for inverter units.

• At the aircon: 740 × 8 × 0.5 = 2,960 Wh
• From the battery, with our runtime calculator’s 85% AC figure: 2,960 ÷ 0.85 = 3,482 Wh

A DELTA 3 Max (2,048 Wh) falls short. A DELTA Pro 3 (4,096 Wh) covers it with a little to spare. For a full sizing table at different hours and watts, see what size battery runs a 1HP aircon overnight.

How much sun refills it

The array must put about 3,500 Wh back the next day. With an example of 4 peak sun hours and about 80% of panel watts reaching the battery:

Panels needed ≈ 3,482 ÷ 4 ÷ 0.8 ≈ 1,090W, before any daytime aircon use.

Verified DELTA Pro 3 setups (both inputs can be used together, up to 2,600W in total):

Cable note for the High-PV input: EcoFlow’s manual specifies a “Solar to XT60 Charging cable”. It doesn’t say whether the 220W panel’s included XT60i cable fits that port, so confirm before you buy. These portable panels can be set up by the owner following the manual.

The home-system version

A wired system does the same job with a hybrid inverter and a battery bank. One example is the PowMr 6.5kW hybrid inverter (48V): PowMr’s catalogue lists 6,500W output, 50Hz or 60Hz, lithium or lead-acid batteries, and an 80A utility charger. The same day-night maths applies to the battery bank (LiFePO4 guide). Anything wired to the house, roof or grid needs a licensed PEE, an LGU electrical permit and, for export, the net-metering process. Find help on our installers page.

Stretch the night

• Choose a low-watt unit: the TCL TAC-11CSD/P7 is 650W rated.
• Set it to 24°C, as the DOE recommends, and use the sleep or timer mode.
• Pre-cool the room before sunset while the sun is still charging the battery.

What to buy

• EcoFlow DELTA Pro 3: Lazada (EcoFlow PH) · Shopee
• Panels: 6 × EcoFlow 220W on Lazada + 1 × EcoFlow 400W Lightweight on Lazada
• Aircon: TCL TAC-11CSD/P7 on Lazada · Shopee, or Kolin KA-100GQAIINV32 on Lazada
• Wired option: PowMr 6.5kW hybrid inverter on Lazada, installed by a licensed electrician

Check today’s price before you buy.

Bottom line

At night, the battery does all the work. Size it for the whole night (watts × hours × 0.5 ÷ 0.85 in our example), then size the panels to refill it in one day’s sun. For a 1HP inverter unit, that means a DELTA Pro 3-class battery and around 1,100W or more of panels.