Save cash when cooling air

Q: With these crazy gasoline prices, we stay home more now, don't travel and, therefore, air condition more. My old central air conditioner costs a lot to operate. What type of replacement unit will be cheapest to run?

A: There are many new super-high-efficiency central air conditioners available, and many use Earth-friendly (ozone-safe) R410A refrigerant. Assuming your old air conditioner is of typical efficiency, installing a new one with the highest SEER (seasonal energy efficiency ratio) of 21 will consume less than 50 percent as much electricity as your old one.

Also, the newer outdoor compressor/condenser unit operates more quietly than old ones.

The payback period from the utility bills savings depends upon your climate and the efficiency of your house. Particularly if your house is not energy efficient (old windows, little insulation, leaky ductwork, etc.), the 50 percent savings can provide and excellent return on your investment. It also helps the environment.

Since you want a new central air conditioner with the lowest operating cost, have your heating/cooling contractor provide a quote on a two-stage model with a variable-speed ECM blower motor and matching thermostat. This setup can cost several thousand dollars more than the cheapest single-stage model.

If you go this route, your contractor will likely recommend you also install a new two-stage or modulating furnace at the same time. This is because the furnace and central air conditioner use the same controls, thermostat and blower motor. Even if you do not install a new furnace, you will have to install a new indoor cooling coil to attain the high efficiency.

A two-stage model operates at a low-cooling-output level about 80 percent of the time. This uses less electricity and provides more even cooling.

With the newest communicating thermostats, the indoor air temperature varies less than one-half degree from the setting. This allows you to set the thermostat a degree or two higher for more savings without sacrificing comfort.

With a TAM or SAM (telephone or system access module), you can change the setting remotely.

Even though it costs a little more, install a variable-speed blower motor. This allows the cooling system to constantly vary the air flow for maximum cooling or maximum dehumidification or any combination you like. This also lowers the indoor noise level from the air flowing through the ducts.

Write for Update Bulletin No. 921, or instantly download it at www.dulley.com. It includes a buyer's guide of the most efficient 2008 central air conditioners listing stages, output, SEER, refrigerant, sound level, warranty, and a payback chart. If you write for the bulletin (the address is at the end of this column), please include $3 and a business-size, stamped, self-addressed envelope.

Q: We have an 8-acre lake on some property near our house. We want to try to use hydro power to generate electricity for our house. Is it possible to set up a small hydroelectric system at the lake?

A: Hydroelectric generation systems are very effective and efficient on a large scale. As with most power generation systems, the economies come with scale meaning larger systems are more cost effective.

The rate of flow of the stream feeding your lake and the height of the dam are more important than the size of the lake. For an 8-acre lake, there likely will not be enough water flow to make a hydro system feasible.

Send inquiries to James Dulley, The Post and Courier, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.