>>The rule of thumb is 2.5 tons per 1000 square feet.
>>So to answer your question, it will work, but you will end up using more energy as >>this system is undersize for your needs.
This guy has been answering many of these with the same grossly incorrect information
An undersize system will not use more energy than a properly sized system. It will not be able to keep the house at the desired temperature. This is like a using a Golf cart to drive around town.
The opposite is true: An over-sized system can cost more to operate than the right size system. The right size system is sized to keep the house at the desired temperature during the hottest times of the year. An over-sized system as too much capacity and will cycle off and on (short cycling) much more frequently as even on the hottest days more than half the day is spent at less than full load, like mornings and evenings. It is similar to city vs. highway driving. The AC unit must run 3-5 minutes just to reach the rated efficiency. If it runs 10 minutes - 5 of that is the initial cool-down then you may be actually getting only 60-70% of the rated efficiency.
The Right Way - ACCA Manual J
1) The proper way to size HVAC systems is with the calculation process described in ACCA Manual J. There are some approved software programs that do this for you and there are some freebies on the web that can give an approximation. It takes into account things like windows size and types, insulation in walls and ceilings, location of the house.
However, it takes a little time to do this so often there are "rules of thumb" that contractors use to get a quick estimate. However, if you get a quote from a company for new HVAC and they don't offer to perform a Manual J as part of the job, then find another HVAC company because this one is cutting corners. If you are replacing an existing system and have made improvements to the insulation, window, air-seal, etc. then a new Manual J load calculation should be performed.
Many HVAC companies will try to install much larger than necessary systems. Partially because they can charge more, but also because it covers builder and installer errors and can reduce complains on the hottest days that the system is not working or is not big enough.
However, it is important to know that a too large system will cool your house too quickly and not dehumidify well. So in a humid place (like Atlanta or Houston) your house will be cold but very clammy.
2) A newer house, reasonably well done in a moderate climate may be just fine with 2.5 tons for a 2000 sq foot house. However, you must understand that a 2.5 ton system in a 2000 sq foot house in a humid environment like Atlanta will be different that a 2.5 ton system in the Nevada desert.
In one case a 2.0 ton system in a 2000 sq foot house in S. California works well.
One ton of air conditioning can cool approximately 600 square feet of area, if the climate is not too hot and humid. Using that formula, a four-ton air conditioner can cool about 1600 square feet of area.
600 square feet.
about 75000 btu
Yes, a 4.5 ton air conditioner would be the minimum size for 2000 square feet.
1500 sq ft.
300 square feet, or about 15 x 20 feet.
around 400 SF, not ft