How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
Should I repair or replace my old air conditioner?
Saturday, October 6, 2018
Generally, from an accountant’s total-cost standpoint and allowing for the time-value of the delayed expenditure for a new system, it’s less expensive to nurse your existing a/c unit until it dies. But one other factor may tip the scales toward earlier replacement: already-inefficient air conditioning systems get even less efficient as they get older, especially after about 20-years. The compressor draws more amps as it ages, and the temperature split (difference between the ambient room air and the cold air coming out the ducts) tends to decrease too. Your a/c service tech can give you a rough evaluation of the system’s current efficiency as a guide when you’re trying to decide whether to repair or replace.
Although the SEER rating is not marked on older units, the average SEER for a system manufactured from 1970 to 1996 was between 9 and 10, trending up gradually towards 12 between 1997 and 2006. If your current SEER is 9 or below, then a new system will be at least 40% more efficient. So replacing an HVAC system that is 20-years old or more will make a significant dent in your monthly electric bill.
When it is time for replacement, systems with SEER ratings up to 20 and beyond, like the one shown above, are available. Each notch of efficiency means more initial outlay and, for the very high SEER systems, more maintenance because of the more complex components. For most situations, the minimum or near-minimum SEER is the most cost-effective choice; but the length of the cooling season and cost of electricity in the region can change the equation. At the southern tip of Florida in Key West, for example, where the cooling season is longer and the cost of electricity is higher than normal, a high-SEER system makes both environmental and budget sense.
Also see our blog post What is the SEER of my old air conditioner?
To learn more about heating and air conditioning systems, see these other blog posts:
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