Understanding the Costs of Installing a New AC in an Older Home

Older homes across San Diego County often weren't built with central air in mind. That doesn’t mean they can’t be made comfortable—it just takes a thoughtful approach. If you’ve been relying on portable units, window systems, or the occasional ocean breeze, you already know those solutions don’t always hold up during San Diego’s heat waves. And while the climate here is relatively mild, certain summer stretches can turn your home into a sauna if your system isn’t up to the task.

Installing air conditioning in a home without ductwork might sound overwhelming—but with the right planning, expert guidance, and system selection, it doesn’t have to be. In fact, this upgrade often leads to better energy efficiency, more consistent indoor temperatures, and improved air quality. That’s a win for both comfort and long-term value.

Below, we’ll explore how San Diego homeowners can confidently upgrade their comfort systems—even in older homes—by breaking down costs, comparing system types, and explaining what factors truly drive project pricing.

Factors That Affect the Cost of Installing AC in a Home Without Central Air

Every home tells a different story, and those details directly influence installation costs. When planning your project, consider the following:

Home size and layout. A 1,200-square-foot bungalow won’t have the same cooling demands—or installation costs—as a 2,500-square-foot home. Open-concept layouts are generally easier to cool, while multi-level homes and properties with many small rooms may require more complex solutions.

Age and construction. Many older San Diego homes weren’t designed for central air, and the electrical infrastructure often reflects that. If your electrical panel can’t support a new system, upgrades may be required—costing thousands depending on your setup.

Existing infrastructure. If your home lacks ductwork, adding it means opening up walls, crawl spaces, or attics. This labor can account for a large portion of the project cost, especially in homes with tight spaces or limited access.

Location within San Diego County. Coastal properties have different needs than inland homes where heat is more intense. Plus, permit requirements and labor costs can vary depending on your city or neighborhood.

Insulation and weatherproofing. If your home loses cooled air due to poor insulation or outdated windows, your system will work harder—and you’ll pay more in energy costs. In some cases, weatherproofing upgrades can reduce the size (and cost) of the AC system you need.

Cost Breakdown by AC System Type

Choosing the right system means aligning your budget, your comfort needs, and your home’s unique characteristics. Here’s how the most common options compare:

Ductless Mini-Split Systems

Ductless systems are a favorite for older homes without existing ductwork. They’re compact, efficient, and less invasive to install.

• Single-zone systems: $3,000–$5,500 installed

• Multi-zone systems: $5,000–$12,000+ depending on zone count and layout

Installation is relatively simple—outdoor units connect to wall-mounted indoor units through small openings. Many homes can use their existing electrical infrastructure, saving on upgrade costs.

Central Air Conditioning with New Ductwork

While more expensive upfront, a full central AC installation with ductwork delivers true whole-home comfort. In San Diego:

• Complete systems: $7,000–$18,000

• Premium systems or complex installs: $20,000–$25,000+

A major portion of that cost is ductwork: $3,000–$8,000 alone depending on home size and accessibility.

Window and Portable AC Units

Best for spot cooling, these systems require little to no professional installation:

• Window units: $150–$800 per unit; $300–$1,100 installed

• Portable units: $200–$860 depending on features and capacity

These aren’t whole-home solutions and consume more energy per cooling capacity. They work best for renters or temporary relief—not long-term efficiency.

Hybrid or Zoned Systems

Combining technologies—like central AC in main living areas and mini-splits in hard-to-reach rooms—can balance comfort with budget constraints.

This approach is growing in popularity in historic and custom homes where preserving architectural features matters.

High-Efficiency Systems

ENERGY STAR® certified systems may cost 10–20% more up front, but they can save 15–30% on cooling costs annually. In San Diego’s long cooling season, that adds up over a 15–20 year system lifespan.

Additional Costs to Consider

Don’t forget these extras—they can impact your final investment:

• Electrical upgrades: $1,500–$4,000 for panel upgrades; $500–$1,200 per new circuit

• Permits and inspections: $100–$800 depending on city regulations

• Custom ductwork solutions: For unusual layouts or inaccessible spaces

• Insulation/weatherproofing: $1.50–$3.50/sq. ft. for attic insulation upgrades

• Thermostats and controls: $150–$500 depending on features

• Outdoor prep: Concrete pads, trenching, or minor landscaping

• Air quality add-ons: $200–$2,500 for filtration, purification, or UV upgrades

Financing and Rebates for AC Installation

Installing a new system doesn’t have to mean paying out of pocket all at once.

• Manufacturer financing: Many brands offer 0% options for qualified buyers

• Contractor financing: Allegiance Heating & Air offers financing with streamlined applications and competitive terms. Explore financing here

• Home equity or personal loans: Use home equity or apply for fixed-term loans through your bank

• Rebates and incentives: SDG&E and federal programs offer $200–$2,000 in rebates and tax credits for energy-efficient systems

How to Choose the Right AC System for Your Home

Here’s how to approach the decision:

1. Know your comfort priorities. Which rooms matter most? Do you work from home? Sleep hot?

2. Evaluate how long you’ll stay. Long-term homeowners benefit more from high-efficiency systems

3. Consider layout and construction. Older homes may not be ideal for ductwork—but great for mini-splits

4. Check system sizing. Too big or too small both cause problems. Get a professional load calculation.

5. Review warranties. Aim for 10–12 year manufacturer coverage and at least one year for installation

6. Schedule during off-peak seasons. Spring and fall often yield better pricing and availability, be sure to check for coupons, promos, and specials.

Can You Install AC in Your Older Home?

Yes, you can install air conditioning in a home without existing ductwork—and you can do it in a way that’s efficient, reliable, and tailored to your space. Whether you're leaning toward a ductless system, planning a central install with new ducts, or exploring a hybrid approach, understanding your options—and your home’s unique needs—is key.

If you're ready to explore what’s possible, we’re here to help. Allegiance Heating & Air Conditioning has been working with San Diego homeowners since 1984. We know these homes. We know this climate. And we’ll help you choose a system that feels like it was made for your home—because it was.

Contact us for a free consultation and custom estimate today.