Dear Jim: 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? – Karlene M.
Dear Karlene: 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 includes 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 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 on the activities you are doing in various rooms, you may not have to keep them all 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. Window adapters are included with all the models. These are typically designed to fit into vertical or horizontal slider windows, but you should be able to rig up an adapter for casement windows.
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 heated overall by using it in this fashion.
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.
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.
Dear Jim: 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? – Bob R.
Dear Bob: 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.