A portable air conditioner can save money

Q: I am trying to run my central air conditioner less to save electricity. Would using a portable air conditioner use less electricity? Does one have to be vented outdoors through a window?

A: Anytime you exchange the use of an energy-intensive large central air conditioner with a cooling appliance that uses less amperage, you reduce your electric bills. These cooling appliances include window and portable air conditioners, whole-house fans, ceiling fans, etc.

The latter two options, both fans, use the least amount of electricity, but they technically do not cool the air. A ceiling fan just makes you feel cooler by creating a breeze in the room. A whole-house fan does bring in cooler outdoor air, typically at night, but high humidity may be a problem.

Depending upon its size (cooling capacity in British thermal units per hour, or Btuh), using a portable air conditioner may use just one-eighth as much electricity as your central air conditioner. Keep in mind though, it will cool only one room or one area (called zone cooling), so your entire house will not be as cool.

This zone cooling can be an effective energy-saver though. Depending upon the activities you are doing in various rooms, you may not have to keep them all extremely cool. Sometimes running just a ceiling fan may create adequate comfort. For example, there is no need to keep the entire house cool at night when you can run a portable air conditioner in your bedroom.

A portable air conditioner does have to be vented outdoors through a window to provide cooling. A flat adapter panel is used to connect the portable air conditioner or heat pump to a window with one or two, 5-inch-diameter flexible and collapsible ducts.

This is where the heat, which is pulled from the room air, is exhausted outdoors. The window adapter and ducts, which must be moved along with the portable air conditioner, fit most easily in single- or double-hung or slider windows and sliding glass doors.

Use 1-by-1-inch foam weatherstripping to seal the window edge against the panel. Hollow round foam pipe insulation also works well. Use tape or glue to secure the foam to the panel to simplify moving among windows. To use with a casement window, you must make a triangular top and bottom end caps to seal in the window opening.

Select a model with several blower speeds and adjustable directional louvers. When cooling, adjust the louvers to direct the cooled air up at about a 30-degree angle. The cooled air blowing out is denser so directing it upward keeps it from settling down to the floor.

Instead of buying just a portable air conditioner, consider a heat pump model. It is not a lot more expensive and you can use it for zone heating during winter to also reduce your heating bills. Even if you have inexpensive natural gas heat, zone heating this way may still save overall.

I use a portable heat pump model in my own home/office for year-round savings. Portable heat pumps, which look identical and operate similarly to a portable air conditioner, also provide heating during cold weather. This efficient heating source can produce up to 12,000 Btuh from a 120-volt electrical outlet. Most electric space heaters produce only 5,100 Btuh.

The thermostat is built into the handheld remote control so it senses the temperature where you are sitting, not at the unit itself. This is an advantage because you really need to have it comfortably cool precisely where you are in a room. With sun shining in windows on a hot afternoon, the temperature can vary significantly throughout a large room.

If you are doing a particularly energetic activity and just want to have cool air blowing directly on you, a portable air conditioner can be used unvented. Even though the air feels cool blowing on your skin, the room you are in is actually being slightly heated overall by using it in this fashion. This is similar to how running a fan makes you feel cooler, but actually heats up the room.

You will have the option of selecting a one- or two-duct model. Two-duct models are generally more efficient because no room air is being lost outdoors. With a one-duct model, indoor air is being drawn through the condenser coils for cooling and exhausted outdoors. If high humidity is a problem in your area, select a model with a dehumidification mode for comfort.

The following companies offer portable air conditioner/heat pumps: Danby, (800) 263-2629, www.danby.com; LG, (800) 423-4142, www.lg.com; Soleus Air, (877) 665-9765, www.soleusna.com; Sunpentown, (800) 330-0388, www.sunpentown.com; and Toyotomi, (203) 775-1909, www.toyotomiusa.com.

Q: We try to keep our house as airtight as possible. We recently had new plumbing installed and there are some holes in the walls under the kitchen sink. Should we be concerned about sealing these?

A: If the holes are on an inside wall, from an energy efficiency standpoint, there probably is no need to seal them. On a windy day, hold your hand under the sink near the holes to check for drafts to be sure.

You may still want to seal the holes to keep insects and mice from getting under the sink. They are drawn to moisture and food particles. Shoot a bead of caulk around pieces of scrap drywall and stick them over the holes.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit dulley.com.