Usually a non variable speed motor is a three speed motor.
BC, the variable speed motor on most furnaces will use 2/3 less energy.
With variable speed, you can also over come some static pressure issues due to existing duct design that you wouldn't have with a non variable speed (however, variable speed should not be used as a band aid for poorly designed duct systems).
Is the 16 SEER unit a two stage compressor? Usually a two stage Copeland will run 67/100 depending on the load requirement in the house. On first stage, with variable speed (with lower CFMs of air over your coil), you'll reach a comfort level due to humidity removal that you would never obtain with a non variable speed system. Bottom line, you can set your t-stat at a higher temperature and still feel as comfortable comapred to a lower setting with higher humidity (72 degrees with 55 RH in the house feels less comfortable to the average human than say 75 degrees at 43 RH). One the first stage with the compressor (on a two stage compressor), you also use less energy than a single stage compressor. With a two stage compressor, you may run it on single stage up to 80% of the time the equipment is in use, if sized properly.
Usually, a two stage compressor is on 16 SEER equipment or higher. Thus, you pay more for a 16 SEER unit due to other variables than just the SEER rating of the equipment.
Usually a good HVAC contractor can explain the differences and why the price difference.
Personally (IMO) once you go over 14 SEER, you won't see the payback (Or ROI
) due to the increase in price of equipment, however, you will get a higher comfort level. Manufacturers don't sell their higher end equipment on "bells and whistles", they sell them on comfort (which is a fact).
I do however wonder why one system is 3 tons (16 SEER) and the 13 SEER is 3.5 tons (I'm assuming for the same house?). With Copeland two stage compressors, you don't have 1/2 ton increments (sp?). Usually you go a size higher than lower and let the compressor run on first stage to meet the load requirements than going a size lower, and run the risk of not being able to meet your load requirements for the house.
A general rule of thumb from information obtained from numerous power companies, from 13 to 14 SEER, you'll roughly save $7 per month on your electric bill (other variables could have an affect on that number).
On a side note, keep in mind, anyone now a days who just puts in an R22 system, after 2010, R22 units will no longer be made. Currently, R22 just took another massive price increase and we're still two years away from one of the federal mandates. Supply and demand. R22 goes up in price, R410A goes down in price. By 2030, all prodcution of R22 will cease (and production gets limited in the meantime during different timeframes set forth by the goverment).
