How to Lower Your AC Electric Bill in Hawaii

01The short answer: how to cut AC costs on Oahu

The fastest ways to lower your AC electric bill in Hawaii are to raise the set point a few degrees, cool only the rooms you use, keep filters and coils clean, and block the sun before it heats your home. The bigger long-term savings come from replacing old, oversized or fixed-speed units with a right-sized inverter split AC and pairing it with rooftop solar if you have it.

Here is why it matters so much here. Honolulu residential electricity averages about 43 cents per kWh, roughly 2.3 times the U.S. average. As a simple example, an AC drawing 1 kilowatt for 8 hours a day uses 8 kWh, or about $3.44 a day at that rate. That is about $103 a month for one unit, before you count bedrooms running overnight.

021. Use smarter set points and settings

These cost nothing and start saving today.

• Aim for about 78°F when you are home. This is the U.S. Department of Energy's recommendation for cooling. Every degree you go lower makes your system work harder.
• Add ceiling or standing fans. The Department of Energy says fans can let you raise the set point about 4°F with no loss of comfort. Fans cool people, not rooms, so turn them off when you leave.
• Raise the temperature when you are away. The Department of Energy estimates you can save up to about 10% a year on heating and cooling by adjusting your thermostat 7 to 10 degrees for 8 hours a day.
• Avoid the 'blast it cold' habit. Setting 65°F does not cool the room faster. It just keeps the unit running longer.
• Use scheduling. Wi-Fi controls and timers can pre-cool a bedroom before bed instead of cooling it all afternoon.

032. Cool only the rooms you use

Many older Oahu homes were built for the trade winds with no ductwork, which is why ductless split AC became the go-to retrofit. One of its biggest advantages is zoning: each room has its own indoor head and its own setting.

Turn off heads in empty rooms, and keep doors closed in rooms you are cooling. On a central system, avoid closing too many vents, since that can strain the system. If you are cooling the whole house to keep one bedroom comfortable, adding a mini-split for that room can make more sense than running central AC all night.

043. Keep your AC clean and maintained

Dirty filters, a dusty coil, and a salt-crusted outdoor unit make any AC run longer to deliver the same cooling. In Hawaii, humidity feeds mold on indoor coils, vog clogs filters, and salt air coats outdoor coils in coastal neighborhoods.

Rinse split AC filters every few weeks during heavy use, keep plants and clutter away from the outdoor unit, and schedule professional AC maintenance at least once a year. Hawaii Energy offers a $75 instant rebate on a qualifying AC tune-up through participating contractors, subject to program availability.

054. Upgrade old equipment to an efficient inverter system

Older window units and fixed-speed systems run at full power, shut off, and start again. Inverter split ACs and heat pumps adjust compressor speed to match the load, so they spend most of their time running gently, which uses less electricity and holds a steadier temperature.

When you compare systems, look at the SEER2 rating, the current federal efficiency standard. Higher SEER2 means more cooling for each kWh. At Oahu's electricity prices, the gap between an old unit and an efficient new one adds up quickly, and our AC installation team can price options side by side. To see what an upgrade would save on your own bill, enter your unit's size, rating and hours in our AC running cost calculator.

Hawaii Energy rebates

Hawaii Energy offers instant rebates of $400 to $550 per qualifying mini-split outdoor unit, set by size and SEER2 rating ($450 for the 9,000 and 12,000 BTU units in most bedrooms, at 17.2 SEER2 or better), and $1,250 for a qualifying central AC retrofit. ENERGY STAR window ACs can earn $25 to $45 at participating retailers. Rebates are first-come, first-served, require a Hawaiian Electric bill, and are subject to program availability. See our Hawaii Energy rebates page for what qualifies; we show you which rebate tier each option falls in.

Right-size it

Bigger is not better. An oversized AC cools the room quickly, shuts off before it removes much humidity, and cycles on and off, which wastes energy and leaves the room clammy. An undersized one runs nonstop. A proper load calculation looks at room size, windows, sun exposure, insulation and how the space is used. Our guide on what size mini-split you need explains the basics.

065. Pair your AC with solar

Hawaii's sunniest hours line up with when homes need the most cooling. If you have rooftop solar, run your AC during the day while your panels are producing and let the house pre-cool before evening. Under many of Hawaiian Electric's newer solar programs, using your own solar power at home is often worth more than sending it back to the grid.

With a home battery, stored midday solar can carry your AC into the evening. If you are planning solar and a new AC, size them together so the system you install matches the load your panels will carry.

076. Block the heat before it gets in

Every bit of sun you keep out is heat your AC does not have to remove.

• Close blinds and curtains on sun-facing windows, especially west-facing glass in the afternoon. Leeward homes in Kapolei and Ewa Beach feel this the most.
• Add window film or exterior shades on windows that take direct sun. Shading outside the glass stops heat before it enters.
• Seal gaps around doors, windows and old jalousie windows so cooled air stays in and humid air stays out.
• Check the attic and roof. Attic insulation, ventilation and a light-colored or reflective roof reduce the heat that radiates into living spaces.
• Shade the outdoor unit with open-air landscaping that does not block airflow. Keep at least a couple of feet clear on all sides.

08When to call a pro to lower your cooling costs

If your bills are climbing and the AC seems to run constantly, have it checked. A dirty coil, low refrigerant or a failing part can quietly drive up your usage. Book AC maintenance and we will clean the system and tell you what we find.

If your system is older, oversized or still running on a fixed-speed compressor, ask us for an AC installation estimate. We will size it for your home, show you efficient options with their SEER2 ratings, and show which Hawaii Energy rebates each option qualifies for. Call (808) 400-6593 to get started.