Every spring the same conversation happens. The RTU needed a repair last fall. It needed one the spring before that. Now the building owner is standing in front of an estimate and wondering if it’s time to stop throwing money at this unit. That’s a fair question, and the answer isn’t always obvious. Here’s how to think through it.
How Long Should a Commercial Rooftop Unit Last?
Most commercial rooftop units have a realistic service life of 15 to 20 years with proper preventative maintenance. Some units outrun it. Older Trane and Carrier units from the early 1990s still show up on rooftops across Morris, Essex, and Bergen County, running reliably because they were built heavier and maintained consistently.
On the other end, some units from 2012 to 2015 are already failing. Build quality varies. A 12-year-old unit with documented filter changes and annual inspections is in a very different position than one that got ignored until something broke.
Age is a data point. Condition is what drives the decision.
The 50% Rule
Most HVAC contractors use some version of this: if a single repair costs more than 50% of what a replacement unit would cost, replace it. Some use 40%. Either way, the logic holds.
A compressor replacement on a mid-size Carrier or York rooftop unit is not cheap, and when you stack that against the cost of a new unit of similar tonnage, you’re often closer to replacement territory than the repair quote suggests. That’s before factoring in the age of the rest of the equipment.
The rule applies across multiple repairs too. Add up what you’ve spent on that unit over the past two or three years. Repeat calls for refrigerant leaks, failed boards, and motor replacements add up faster than most owners realize.
Signs It’s Time to Replace
- R-22 refrigerant. R-22 was phased out in 2020. Current prices run $100 to $150 per pound or more. A system that needs a charge every season is burning money on a refrigerant you can only get from recovered stock.
- Compressor failure on a unit over 12 years old. Replacing the compressor on an aging unit often means the next failure is a fan motor, a heat exchanger, or a control board. You’ve rebuilt one part of a worn-out machine.
- Cracked heat exchanger. Safety issue first, cost issue second. Combustion gases can enter the building air stream. Replace the unit.
- Control boards failing repeatedly. One board failure can happen. Two or three on the same unit within a few years points to something deeper.
- Energy bills climbing with no other explanation. Degraded refrigerant charge, dirty coils, and worn compressors reduce efficiency without triggering obvious fault codes. If cooling costs keep rising and usage hasn’t changed, the unit is working harder than it should.
- Parts getting scarce. When lead times stretch to four to eight weeks, a single failure could leave your building without cooling for a month.
Signs Repair Still Makes Sense
- Single component failure on a unit under 10 years old with a solid maintenance history.
- The part is available same-day or next-day. No extended downtime risk.
- Repair cost lands at 20 to 30% of replacement cost, not 50%.
- Coils are clean, cabinet is in good shape, refrigerant type is current (R-410A or R-454B), and the rest of the unit checks out.
A Daikin or Lennox unit from 2018 with a failed ECM motor is a good repair candidate. Years of life left, common part. Fix it.
What Commercial RTU Replacement Actually Costs in NJ
Commercial RTU replacement in New Jersey typically runs $8,000 to $25,000 per unit, depending on tonnage, efficiency, and installation complexity.
A 5-ton unit swapped onto an existing curb is a straightforward job. A 20-ton AAON unit requiring a crane, new curb fabrication, gas line work, and electrical upgrades is a different project. Crane costs can add $1,500 to $3,000. New curbs, disconnects, and gas piping can push the total 15 to 20% above the equipment cost.
Get a full scope of work in writing before comparing bids. Two quotes at different numbers often reflect different scopes, not just different prices. See our guide to choosing a contractor for what to look for.
The Efficiency Math Is Real
An older unit running at 10 SEER replaced with a 16 SEER unit uses meaningfully less electricity for the same cooling output. The basic SEER efficiency math (1 minus the ratio of the old SEER to the new SEER) works out to roughly a third less cooling energy consumption, and ENERGY STAR notes that certified light commercial HVAC equipment uses about 17% less energy than standard new equipment, with older units falling well below that baseline. On a 20-ton unit running through a full New Jersey summer, that reduction shows up on the electric bill every month from June through September.
Several NJ utilities offer rebate programs for qualifying high-efficiency commercial HVAC equipment. PSE&G and JCP&L both run programs that can offset part of the equipment or installation cost. A contractor who knows the process can help you apply. See our page on NJ utility rebates for current program details.
The One More Season Trap
Every year, owners decide to run a struggling unit through one more summer. Sometimes it works. Often it doesn’t.
A unit that dies mid-July is a different problem than a planned replacement in March. Emergency calls cost more. Lead times on equipment during peak season stretch out. Temporary chiller rentals can run several thousand dollars per week while you wait on a unit. The savings from skipping a planned replacement disappear fast.
If a unit is showing two or three of the warning signs listed above, have the replacement conversation in the fall or winter. Equipment availability is better. Scheduling is easier. You control the timeline instead of reacting to a failure.
Questions to Ask Before Replacing
A match-replace isn’t always the right call. Confirm these with your contractor before signing off:
- Load calculation. Has the building use changed? Converted office space, new server room, higher occupancy? The original tonnage may not fit current conditions.
- Curb compatibility. Can a curb adapter work, or does the roof opening need to be reframed?
- Efficiency options. What’s the cost difference between standard and high-efficiency, and what’s the payback given your runtime hours?
- Rebate eligibility. Is the proposed unit on the utility’s qualifying list? Who handles the application?
- Warranty and service terms. What’s covered and for how long?
Talk to KCG About Your RTU
KCG Energy Management handles commercial rooftop unit replacement across northern New Jersey. We assess the equipment, manage the full installation including crane coordination and utility rebate applications, and offer service agreements to protect the investment.
If you have a unit that keeps coming up in maintenance conversations, reach out. We’ll give you a straight assessment and a clear recommendation. Learn more about our commercial HVAC services or contact us to schedule a rooftop inspection.