Step 1 — Get the Right Size

Sizing is the most important decision in any AC purchase. An oversized system short-cycles — it cools the air quickly but shuts off before removing enough humidity, leaving your home feeling clammy. An undersized system runs constantly and can't keep up on the hottest days.

The only correct way to size an AC is a Manual J load calculation. This accounts for your home's square footage, ceiling height, insulation levels, window area and orientation, air infiltration, and local climate data. D's Air performs a free Manual J on every estimate — no guessing, no rule-of-thumb sizing.

As a rough guide, Chicago homes typically need 400–600 square feet per ton of cooling. A 1,500 sq ft home might need 2.5–3 tons. But the calculation is required for an accurate recommendation — don't let any contractor skip it.

Step 2 — Choose Your Efficiency Level

New AC equipment is rated in SEER2 (Seasonal Energy Efficiency Ratio 2). The minimum for Chicago is 13.4 SEER2. Most homeowners benefit from 15–16 SEER2, which provides meaningful savings over minimum equipment at a reasonable price premium.

Variable-capacity systems (19–20+ SEER2) deliver the best comfort and efficiency but cost more upfront. They're worth considering if you plan to stay in the home long-term or if comfort is a priority. See our SEER2 guide for a full breakdown.

Step 3 — Understand the Refrigerant

All new residential AC equipment uses either R-454B or R-32 — lower-GWP refrigerants that replaced R-410A under EPA regulations effective January 1, 2025. If you're replacing an older system that uses R-22 or R-410A, the new equipment will use one of these newer refrigerants.

This is not a concern for homeowners — the refrigerant is handled entirely by the technician. Just know that if your existing system uses R-22, replacement refrigerant is expensive and scarce, which is one more reason to replace rather than repair.

Step 4 — Consider the Full System

A central AC system has three main components: the outdoor condenser unit, the indoor evaporator coil, and the air handler or furnace that moves air through your ducts. When you replace the condenser, you should also evaluate the coil and air handler.

Matched systems: Manufacturers design condensers and coils to work together. A mismatched coil can reduce efficiency, void the warranty, and cause reliability problems. D's Air always recommends replacing the coil when replacing the condenser on a system older than 10 years.

Ductwork: If your ducts are leaky, undersized, or poorly designed, even the best AC won't perform well. D's Air inspects ductwork on every installation and will flag any issues that need to be addressed.

Step 5 — Compare Brands

The major residential AC brands — Lennox, Carrier, Ruud, Goodman, Daikin, and others — all produce reliable equipment when properly installed. Brand matters less than installation quality. A well-installed mid-tier system will outperform a poorly installed premium system every time.

That said, there are real differences in warranty terms, parts availability, and efficiency tiers. D's Air installs Lennox, Ruud, Goodman, Carrier, Daikin, and Sinclair equipment and can help you compare options based on your budget and priorities.

Step 6 — Understand What's Included in the Price

When comparing quotes, make sure you're comparing the same scope. A complete AC installation should include:

• The condenser unit and evaporator coil
• Removal and disposal of the old equipment
• Refrigerant charge (R-454B or R-32)
• City of Chicago mechanical permit and inspection coordination
• Electrical disconnect and wiring (if required)
• Condensate drain line inspection or replacement
• Thermostat verification and programming
• Manufacturer warranty registration
• Contractor workmanship warranty

D's Air includes all of the above in every installation. The installed price you're quoted is the price you pay — no surprise add-ons after the job starts.

Step 7 — Ask About Financing

A new central AC system is a significant investment — typically $5,900 to $14,000 installed depending on size and efficiency tier. D's Air offers financing options for qualified customers, including 0% interest promotions. Ask about current offers when you call for your free estimate.

Questions to Ask Every Contractor

• Will you perform a Manual J load calculation before recommending a size?
• Is the evaporator coil included in the quote, or is it separate?
• Do you pull a City of Chicago mechanical permit on every installation?
• What workmanship warranty do you provide beyond the manufacturer warranty?
• Are you licensed and insured in Illinois?

D's Air answers yes to all of the above. IL License #2183457. Call (773) 940-0965 to schedule your free in-home estimate.