The hidden cost of deferred rooftop-unit maintenance.

A 45-minute quarterly coil cleaning costs less than one tenant complaint email. That's the entire argument — but let's walk through why, because the math is more damning than it looks.

Commercial rooftop units fail two ways. They fail loudly (a compressor locks up at 2 p.m. on a Sunday in August, and you're paying overtime plus rental chillers). And they fail quietly — a coil slowly silts up, static pressure creeps, the supply-air temperature rises three degrees, tenants complain about "the air isn't working," and you dispatch a truck to find nothing obviously broken.

Quiet failures are more expensive than loud ones. Here's why.

The three costs nobody itemizes

When a unit is running at 80% of its design capacity because nobody has touched the coil since installation, three things are happening simultaneously — and none of them show up on a maintenance invoice:

1. Energy creep. A dirty evaporator coil can increase compressor run-time by 15–25%. On a 20-ton RTU, that's $600–$1,100 per year in electricity, depending on your rate schedule.
2. Lifecycle compression. Overworked compressors don't hit their rated 15-year life. They hit 8–10. You just paid cash for a unit that retired early, and you probably financed it over 10 years anyway.
3. Complaint overhead. Every tenant email about "the temperature" triggers a truck roll. Even if the tech finds nothing wrong, you've spent $180 and 90 minutes of your day on a ticket that shouldn't exist.

The cheap job scheduled on the calendar always beats the expensive job scheduled by the weather.

What a good quarterly visit actually does

There are PM programs and there are PM checklists. A checklist visit takes 20 minutes and produces a signature. A program visit takes 45–60 minutes and produces a dossier. We run the second kind. Specifically:

• Coil inspection, cleaning, and fin-straightening
• Filter change with MERV-13 minimum (not the MERV-5 the last guy left)
• Belt tension, sheave alignment, bearing lubrication
• Refrigerant pressures and superheat/subcool verification
• Contactor, capacitor, and amperage check on startup
• Drain pan cleaning with biocide tablet replacement
• Static pressure measurement across the unit
• Photo documentation of every point above

The 90-day checklist for facility managers

If you're managing this internally, here's the minimum cadence we'd recommend — written as things your building engineer (or your service vendor) should confirm in writing, not just "do":

• Every 30 days: filters inspected, replaced if needed
• Every 90 days: coils cleaned, drain pan flushed, belts checked
• Every 180 days: refrigerant charge verified, controls tested
• Annually: contactor/capacitor replacement (preemptive), motor amperage logged

The math, one more time

Take a 10-site portfolio with two 10-ton RTUs per site. Twenty units total. A neglected-vs-maintained delta is conservatively $400 per unit per year in energy creep alone. That's $8,000. Add three avoidable emergency repairs a year at $1,800 each — another $5,400. Now the lifecycle math: if you extend unit replacement from year 10 to year 13 by maintaining properly, you've deferred ~$180,000 in capital across the portfolio.

Quarterly PM for twenty units runs roughly $12,000–$16,000 per year. The payback isn't theoretical. It's not even close.

What to ask your service vendor

Three questions will tell you more than any proposal ever will:

1. "Show me the last quarterly report for a comparable property." (If it's a one-page checkmark form, keep shopping.)
2. "Do your PM visits include static pressure measurement?" (If the answer is "what?", definitely keep shopping.)
3. "Will you commit to a photo-documented closeout email the same day?" (If the answer is "we'll get it to you next week," that tells you how fast you'll hear back when something actually breaks.)

The cheap job scheduled on the calendar always beats the expensive job scheduled by the weather. Put the coil cleaning on the calendar.