Last updated: October 9, 2026
Central AC Replacement: A Homeowner’s Planning Guide
Replacing central air conditioning involves more than choosing a brand or matching the old unit’s size. The equipment, ducts, controls, and installation all affect comfort, operating costs, and reliability. This guide helps you compare proposals and identify questions to resolve before signing. It is general information, not a substitute for a load calculation or a contractor’s inspection.
Start with the home, not a square-foot rule
Ask each contractor to document the cooling load and equipment selection for your home. The U.S. Department of Energy explains that rules of thumb can lead to oversized systems; oversizing can raise costs and cause frequent cycling that harms comfort and efficiency. Ask for the assumptions about insulation, windows, air leakage, orientation, occupants, and climate. Request the load calculation and the reason for the selected capacity.
Source: DOE Building Science Education: Proper Sizing of HVAC Systems.
Compare the complete scope
- Exact indoor and outdoor model numbers, capacity, and efficiency ratings.
- Whether existing ducts will be inspected, sealed, repaired, or replaced.
- Electrical, condensate drain, thermostat, permits, and code-related work.
- Removal and disposal, commissioning, startup measurements, and warranties.
- Any proposed refrigerant line or electrical upgrades and why they are needed.
Compare at least two itemized proposals on the same scope. A low equipment price may exclude duct work, permits, or commissioning. National cost figures are not reliable quotes: labor, system type, access, climate, and scope differ widely. Get local written bids and confirm what could change the price.
Efficiency and comfort
SEER2 and EER2 are efficiency measures, but a higher rating alone does not establish the best value for your home. Ask for the model’s rating, expected operating conditions, warranty terms, and how the proposal addresses humidity and room-to-room temperature differences. ENERGY STAR recommends checking filters monthly and changing them when dirty; the correct interval depends on the filter and conditions.
Source: ENERGY STAR heating and cooling guidance.
Questions before approving work
- Can you provide the documented load calculation and equipment-selection basis?
- What duct or airflow problems did you find, and how will you verify airflow?
- Which permits and inspections are included?
- What startup readings and homeowner handoff will I receive?
- What is excluded, and how will change orders be priced and approved?
Check contractor licensing and insurance requirements with your state or local authority, and review written warranty details. Do not choose solely by brand or claimed savings. For related project budgeting, see our HVAC replacement cost guide.
When to get another opinion
Seek a second evaluation if the proposal relies only on square footage, recommends a much larger system without calculations, or cannot explain duct condition and commissioning. A qualified local HVAC professional should inspect the home before final sizing.
