What size A/C unit should I install?
How did the system perform back in '96 or at least on a good charge? Ideally someone preformed all the necessary 'manuals' and it was the correct size to use. I lived in a 1700 sf apartment that was always a little hot until we switched out a 2.5 for 3. It all depends on your heat gain: windows, drafts, insulation, lighting, appliances, humans.... If you are not going to pay an arm and a leg for a professional calculation, I would charge it up one last time and see how it preforms on a nice hot day and then decide if its undersized or just neglected. Charging it back up would cost less than a full load calculation I would think. Or just go with a 3 ton. Although the problems can be just as bad with an over-sized unit, they are much less prone to present themselves then in an under-sized unit. It may cost more to operate but it will work as opposed to it almost works.