by James Dulley
Engineering Consultant
Energy-efficient choices abound when replacing your heating/cooling system
Q: My old heating and cooling system must be replaced. With high energy costs and future energy price volatility, how can I determine the best type to go with?
A: It can make economic, environmental, and lifestyle sense to switch to an entirely different type of heating source for your home. The costs of fuels, such as natural gas, propane, heating oil, and electricity, have shifted dramatically over the past decade. Many new heating systems last 20 years or more, so with wide variations in fuel costs, long-term estimated operating costs and paybacks are not always reliable.
Electricity prices are the most stable and will probably continue that way. For homes heated with electricity, air-source or geothermal heat pumps make good sense because they can heat, as well as cool, your house efficiently.
A standard air-source heat pump is basically a central air conditioner with a few extra parts. The outdoor unit looks exactly the same as a central air conditioner. It is called a heat pump because it literally pumps heat out of your house (cooling mode) or into your house (heating mode) to or from the outdoor air around the outdoor compressor/condenser unit.
Among central heating and cooling systems, geothermal heat pumps provide the highest efficiency and lowest year-round utility bills. While geothermal heat pumps have boasted much higher initial installation costs (due to the need to place loops, or tubing, to run through the ground or to a well or pond), the federal stimulus bill provides consumers (through the end of 2016) a 30 percent tax credit on the cost of putting in a geothermal heat pump system, which makes them much more affordable.
The primary advantage of installing a heat pump of any kind is they can be used year-round for both heating and cooling. This provides year-round savings, and shortens the payback period. In contrast, a super-efficient furnace gets used only during winter and a central air conditioner only during summer.
I use a portable heat pump in my own home/office for year-round savings. In addition to cooling the room during summer, it also functions as an efficient portable heater during winter. It produces 14,000 Btu per hour (Btuh) of cooling and 11,000 Btuh of heating. This is much more heat output than a standard electric space heater using the same amount of electricity during winter.
The efficiency of a portable air conditioner is similar to a window air conditioner. Although this is less efficient than the newest central air conditioners, using one can still save money. By keeping just one or two rooms comfortably cool with clean air, you can set your central thermostat higher and save electricity overall. Use it in the dining room for dinner, roll it into the living room for television, and then to the bedroom for sleeping.
They are typically mounted on castors so they can be easily rolled from room to room. Most operate on standard 120-volt electricity, so they can be plugged into any wall outlet near a window.
A portable air conditioner/heat pump operates similarly to a typical window unit. The internal rotary compressor, evaporator and condenser function in the same way. The primary difference is it is on castors and rests on the floor.
When choosing a heating and cooling system, there are other intangible factors to consider. Every type of system requires some maintenance which can increase the overall costs. A heat pump requires about the same amount of service as an air conditioner.
James Dulley is a nationally syndicated engineering consultant based in Cincinnati.
If you have a question about energy use or energy-efficient products, send it to: James Dulley, Electric Consumer, 6906 Royalgreen Drive, Cincinnati, OH 45244; or visit www.dulley.com.