Robert11 wrote:
Very curious about what it might cost to run the A/C.

The unit is a 3 Ton
Installed in early 1984 (assume SEER of 9. Is this reasonable ?)
Cost of electric is 12 cents per KW Hr.

If the unit is running continuously, what would the cost be per hour ?

Unless it was a "high efficiency" system, 9 SEER sounds a little high
for mid-80's. 8.0 would be more likely, and even that is probably
degraded by the wear and tear on the compressor valves, etc. In any
case at 8.0 SEER, 3T (36K BTU) is 36,000/8 or 4.5KW/h. That should be
close enough to give you an idea of operating costs.

HTH.