A new AC is sized by math, not by sticker.
The most common installation mistake in the valley is also the laziest: reading the tonnage off the old unit’s nameplate and ordering the same. Houses change — windows get swapped, insulation gets added, rooms get built on — and plenty of systems were oversized by the original builder anyway. A proper replacement starts with a load calculation: what this house, with this glass and this insulation, actually needs at 105 degrees. The answer is frequently smaller than the old unit.
Oversizing isn’t a bonus; it’s a defect. An oversized system cools the air near the thermostat so fast it shuts off before it’s dried or circulated the house — short cycles, clammy rooms, a hot back bedroom, and a compressor wearing out on start-stop abuse. The system that runs longer, steadier cycles is the comfortable one. Bigger is not better. Right is better.
California’s current standards set the floor at SEER2-rated equipment, and the rating is worth a minute of your time: it measures cooling delivered per watt consumed, tested under conditions closer to real homes than the old scale. In a valley where the AC runs six months a year, each step up the efficiency ladder is real money off every summer bill — the quote puts the price difference next to the projected savings so the math is yours to make.