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Variable-Speed Systems: The Best of Both Worlds
One major problem brought up by the system sizing discussion has to do with flexibility. Seasons change. A small ton system will dehumidify well but will not be able to keep up in the heat of summer. A large ton system will keep you cool during the summer but will leave the house humid on days when the cooling demand is lower. An in-between sized system is just a compromise between the two.
The solution is a variable-speed system. Variable-speed systems can change their cooling power based on what your home needs. On startup, the system comes on at low-power to dehumidify the home. After a time, if the humidity reaches the set-point but the temperature is still high, the system switches to high power to maximize cooling.
Because these systems only use the cooling power needed, they have an improved SEER (most all models 16 SEER and higher are variable-speed).
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High Efficiency Cost Analysis
The annual energy costs can be calculated from the SEER and Ton ratings of a system as follows:
Using assumptions of a 5 Ton system, 2000 hours of operation per year, and $0.13 per kWh electric cost, the annual utility costs for various SEER systems comes out to the following:
Annual Utility Costs by SEER
- 7 SEER: $2228.57 / year
- 10 SEER: $1560.00 / year
- 13 SEER: $1200.00 / year
- 16 SEER: $975.00 / year
- 20 SEER: $780.00 / year
Note: Systems with Gas Furnaces will need a Variable-Speed Furnace to get the full SEER rating.
