There's no single right answer when a Lennox system breaks down. I've audited six years of HVAC spending—$180,000 across three properties—and the "best" move depends entirely on who you are. A landlord with a rental unit faces different math than a homeowner who plans to stay put.
Here's my framework, broken into three common scenarios. Find yours.
Scenario 1: You Own the Home You Live In
This is the most straightforward case. If the compressor on a Lennox air conditioner fails and you're not moving for 5+ years, lean replacement.
Here's the math from my own house: In 2023, my Lennox AC (10 years old) had a blown compressor. Repair quote: $2,800 for a new compressor + labor. Replacement quote (new 17 SEER unit): $5,400. The difference: $2,600.
To be fair, the repair was tempting. But look at total cost of ownership over the next 8 years. A repaired 10-year-old unit runs at ~13 SEER (if you're lucky). A new 17 SEER unit cuts power use by roughly 25% (Source: U.S. Department of Energy, energy.gov). On my $400/month summer electric bill, that's $100/month saved for 4 months a year. Over 8 years, that's $3,200 in electricity savings. Plus, the new unit gets a full warranty (Lennox offers a 10-year compressor warranty on new registered systems). The repair would only get a 1-year warranty on the part.
The calculation: The $2,600 delta is more than covered by lower energy bills and warranty peace of mind. Replacement wins.
But then again, if your unit is only 3 years old? Absolutely repair. A compressor failure that early is rare, but Lennox warranty usually covers the part (check your registration). You're paying labor only—probably $600-800. That's a no-brainer.
Scenario 2: You're a Landlord with a Rental Property
This flips the math entirely. I've managed HVAC for two rental units. In rental properties, the cheapest functional repair is usually the right answer.
Here's why: tenants don't pay the electric bill in many leases. Or even if they do, you're not capturing the energy savings from a high-SEER unit—the tenant benefits. You're just eating the capital cost.
Take my scenario: A Lennox furnace in a rental failed. Repair quote: $900 (new inducer motor). Replacement quote: $3,700. The delta: $2,800. I'm not capturing any utility savings; the tenant is. I'm not getting a tax credit (unless it's commercial). The only thing I'm getting is a capital expense with no direct return. I went with the repair. To be fair, the tenant did complain about the old system's inefficiency, but that's a retention issue, not a TCO one. I made the repair, and the tenant stayed.
Landlord rule of thumb: If the repair keeps the system running for 2+ years, repair. If the system is over 12 years old and a major component (compressor, heat exchanger) is failing, *then* consider replacement—but only as a last resort. You're delaying the inevitable, but you're also keeping cash in your pocket for other units.
Scenario 3: Commercial Real Estate (Retail/Office)
This is the trickiest. The math depends almost entirely on your lease structure.
I can only speak to domestic operations with triple-net leases (where the tenant pays utilities). If you're dealing with gross leases or different structures, the calculus might be different.
In my experience managing HVAC for a 5,000 sq ft retail complex, a Lennox rooftop unit (RTU) failed in 2024. The tenant was paying the electric bill. The repair (new compressor for a 9-year-old unit) was $3,200. A new high-efficiency RTU was $8,500. Delta: $5,300.
But here's the kicker: the tenant wanted the upgrade. They were high-end retail and wanted to reduce their carbon footprint. So I negotiated: I'd cover the capital cost, and they'd sign a 2-year lease extension. They agreed. I effectively paid $5,300 for lease retention—a great deal compared to the cost of vacancy (easily $20,000 for 3 months of empty space).
Without that, I'd have repaired. But the situation created a different ROI calculation entirely. You need to treat each commercial property as a unique case, factoring in lease terms, tenant quality, and market vacancy rates.
How to Decide for Yourself
Here's a cheat sheet based on my decision matrix:
- Are you staying in the home 5+ years? → Lean replacement (capture energy savings and warranty).
- Is it a rental property? → Repair unless a major component fails on a 12+ year old unit.
- Is it commercial? → Assess lease structure and tenant value. Repair is default; replacement is only for lease retention or major efficiency upgrades.
- Is the unit under 5 years old? → Repair (warranty covers big parts).
Bottom line: Don't let a salesperson tell you always replace. Don't let a tight budget force always repair. Run the numbers for your situation. That's how you actually save money.
Pricing as of Q1 2025; verify current rates with local contractors.
