Don’t think that just because the kids are back in school that the warm days of summer are over. August and September are the hottest months in Hawaii, as this past weekend’s scorching temperatures helped prove.

In fact, 90-plus-degree weather is not unusual for September, or October, for that matter.

More and more new residential subdivisions and condominiums in Hawaii are being built with central air conditioning, keeping families cool but adding to household electricity bills. A 12,000-Btu (British thermal unit) air conditioner – ideal for a 500- to 650-square-foot space – running eight hours per day uses 262 kWh (kilowatt-hours) per month, adding $78 to monthly power bills, according to Hawaiian Electric Co.

A central air-conditioning system for a family of four uses an average of 354 kWh monthly, boosting bills even higher, HECO says. (By comparison, ceiling fans use 24 kWh per month, using $7 worth of electricity.)

If you’re planning to install an air conditioner – either a split central cooling system or a window-mounted unit – it’s important to choose the right-sized appliance based on a "cooling load calculation," HECO says.

Cooling load depends on a number of factors, such as square footage to be cooled, height of ceiling, insulation of walls, window area, direct sun, occupants in area, and temperature and humidity of the outside air. Provide this information to the store or supplier before making your purchase.

For information go to HECO’s website at www.heco.com.

— Star-Advertiser

When the heat is on, your central air-conditioning system needs to work at its best. Here are some tips for getting the most out of your air conditioning in terms of both comfort and energy savings:

1. Block the sunlight. Close window coverings on the sunny sides of the house during the day. You can consider adding awnings or planting trees to provide shade.

2. Close the windows. Air conditioning works in part by removing moisture from the air. If you keep adding humid air to the house, the air conditioner has to struggle to dry it.

3. Clear the condensing unit. The outdoor condensing unit needs a supply of outside air to blow across the heated refrigerant, which is how hot air gets expelled from the house. Make sure the condenser has enough space around it for good airflow. Trim any plants that are growing close to the unit, leaving a clearance of at least 8 inches all around.

4. Seal and insulate ducts. Conditioned air loses some of its coolness as it travels from your air conditioner to your rooms. Some of the loss comes from air leaking out seams and other openings in the ducts, and some occurs because the thin sheet metal conducts heat easily. For do-it-yourselfers, seal ducts with aluminum tape and insulate them with duct insulation wherever they’re exposed. Don’t use duct tape, because the adhesive dries out over time.

5. Check the air filter. If it gets clogged, airflow is reduced. Change or clean it as often as the manufacturer recommends, usually every one to three months.

6. Set the control panel’s fan setting on automatic. Leaving the fan running increases what’s called the stack effect, the tendency of a house to pull in outside air to replace air that rises and escapes through openings high in the building. Also, when the fan runs nonstop, the moving air picks up moisture from the saturated coils when the compressor isn’t running. That defeats the unit’s purpose of drying the air.

7. Install a light-colored roof. If your roof needs replacing, consider a light-colored roof to reflect some of the sun’s heat. Darker-colored "cool roofs" are also available that use special coatings to reflect rays.

8. Leave the oven off. Even when it’s closed, an oven adds as much heat to the air as an air conditioner can take out in the same amount of time. Grill outdoors, order takeout, make a salad for dinner – just try not to cook indoors on the hottest days.

9. Turn out the lights. Incandescent light bulbs turn only 10 percent of the electricity they use into light. The rest becomes heat. Turn off unneeded lights or switch to cooler compact fluorescent bulbs.

10. Use ceiling fans. A ceiling fan moves air over the skin, evaporating perspiration and making you feel cooler. Running one even when the air conditioning is on will increase your comfort. The fans help move air around the room, but only to a degree. It’s not enough of a benefit to justify leaving a ceiling fan on in an unoccupied room, according to the Alliance to Save Energy.

— Mary Beth Breckenridge / Akron Beacon Journal