High Energy Bills & Long Runtime
New equipment only changes what happens inside the cabinet — it does not repair leaky ducts, an undersized duct system, poor insulation, or a heat load that was already too large for the home. If the bill is still high, the most likely explanations are unresolved duct leakage or restriction, a sizing mismatch between the new equipment and the existing ducts, or an envelope or usage factor unrelated to the equipment swap.
If the ductwork was not tested or sealed as part of the replacement, any leakage that existed before the new unit was installed is still there afterward. New equipment cannot compensate for air lost before it reaches the rooms.
A new higher-capacity or variable-speed system moving air through ducts sized for the old equipment can run inefficiently, or the ducts simply cannot deliver what the new unit is capable of producing.
Incorrect refrigerant charge, incorrect airflow setup, or thermostat configuration not matched to a variable-speed or two-stage system can all reduce the efficiency gains a homeowner expected. This is a matter for the installing contractor.
Bills naturally vary with weather. Comparing this summer's bill to last spring's, or comparing without accounting for an unusually hot stretch, can create the appearance of no improvement when there has been one.
Attic insulation, window efficiency, air sealing at the building envelope, and shading all affect load independently of the AC itself. A new unit does not change any of these.
More time spent at home, a lower thermostat setting than before, or new appliances and electronics can raise electricity use for reasons unrelated to the AC's efficiency.
Stick to what you can see, feel and hear. Leave electrical panels, refrigerant, combustion appliances and equipment internals to a licensed professional.
A common assumption is that a new, more efficient air conditioner will automatically produce a lower bill. That's true only for the portion of the system inside the cabinet. The ductwork that carries air from the equipment to the rooms is untouched by an equipment swap unless it is specifically inspected, tested, or sealed as part of the job.
If the ducts were leaking 20 or 30 percent of the air before the new unit went in, they are very likely leaking a similar share afterward. The new equipment may even run more efficiently per hour, but if a meaningful portion of what it produces never reaches a register, the house still needs more total runtime to feel comfortable — which erodes the expected savings.
A duct leakage test performed after installation tells you plainly whether the ducts are working with the new equipment or against it.
Duct Daddy specialises in duct leakage testing and duct sealing. We do not perform mechanical HVAC repair, refrigerant work or equipment replacement. Contact a qualified HVAC contractor if any of the following apply:
In Southeast Louisiana, ducts commonly run through hot, humid attics, which is exactly the environment where leakage costs the most: leaked supply air is lost to attic heat, and leaked return air pulls hot, humid air back into the system.
Because the cooling season here is long, unresolved duct leakage after a new install compounds across many months rather than a short season, which is why it is worth testing rather than assuming the new equipment alone solved the problem.
See the communities we serve.
If the ducts weren't tested when the new equipment went in, a duct leakage test tells you whether they're working with the new system or against it.
Efficiency ratings describe the equipment, not what actually reaches the rooms — losses elsewhere in the system erase the expected savings.
Long runtime after a replacement can be normal variable-speed behaviour, or a sign the equipment is fighting a load or duct problem.
New equipment can only push as much air as the duct system will pass — a restriction upstream limits everything downstream.
The equipment and steps behind a duct pressurisation test, and what each reading measures.
How to tell whether your duct system needs sealing, replacement, or neither.
Browse every symptom in the troubleshooting center.
Schedule a duct leakage evaluation and get measured numbers for your home — not a guess.
