This call comes in differently than most. Nothing’s broken. The house is cooling. Nobody’s sweating in the living room. But the electric bill came in a good deal higher than last July, the family hasn’t changed how they live, and the homeowner wants to know where the money went.
That’s a legitimate service call, and it’s one of the more satisfying ones because the answer is almost always findable. A system that’s cooling but costing too much is a system with a measurable inefficiency in it, and there are only so many places that inefficiency can hide. Here’s how I go looking, and what you can figure out on your own first.
Start by ruling out the easy explanations
Before I blame the equipment I want to know whether the equipment is even the culprit, because two things can move a bill without anything being wrong.
The first is weather. Compare this July to last July honestly, not by memory. A summer that ran several degrees hotter on average, or one that had a longer stretch of triple digits, will move a cooling bill substantially with a perfectly healthy system. Your utility often prints the average temperature for the billing period right on the statement, which makes this easy to check.
The second is the rate. Electricity plans change, promotional periods expire, and a plan that rolled over to a variable rate can raise your bill without a single extra kilowatt-hour being used. Look at the actual usage number in kilowatt-hours, not the dollar amount, and compare that to the same month last year. If the kilowatt-hours are flat and the dollars are up, your problem is a contract, not a condenser.
If the usage genuinely climbed, then it’s worth measuring the system. Here’s what gets measured, in the order I do it.
Runtime: how many hours is it actually running
This is the first number, because it puts everything else in context. An air conditioner’s cost is the power it draws multiplied by the hours it runs. If the draw is normal and the bill is high, the hours went up, and that means the system is having to work longer to hold the same temperature.
Runtime is also something you can watch yourself without a single tool. Sit down on a hot afternoon and time a few cycles. On a genuinely hot day a properly matched system will run long, steady cycles, and near the peak of the afternoon it may run nearly continuously. That’s normal and it isn’t waste. What isn’t normal is a system running around the clock on a mild day, or running constantly and still losing ground against the thermostat.
If runtime is way up, something is either reducing the system’s capacity or increasing the house’s load. Everything below is a way of telling which.
Temperature split across the coil
This is the fastest capacity check in the trade and it’s genuinely simple. I measure the temperature of the air going into the return and the temperature coming out of a supply register, and subtract.
On a system working correctly you’ll typically see somewhere in the neighborhood of eighteen to twenty-two degrees of difference, depending on humidity. A split that’s noticeably narrow means the system isn’t pulling as much heat out of each pass of air as it should, so it has to make more passes, so it runs longer, so the bill climbs. A split that’s unusually wide can mean airflow is restricted, which is its own problem.
You can do a rough version of this at home with a couple of cheap thermometers. It won’t be precise enough to diagnose from, but a split of eight or ten degrees tells you something real is wrong, and that’s worth knowing before you call.
Static pressure, the measurement almost nobody takes
This one is the difference between a real diagnosis and a guess, and I’d say most homeowners have never had it done on their house.
Static pressure is the resistance your duct system puts up against the blower, and I measure it the way a doctor takes blood pressure: with a manometer, before and after the air handler. Equipment is designed to work against a specific amount of resistance, and when the real number is well above that, the blower can’t move its rated airflow. Less air across the coil means less heat moved per minute, longer runtimes, higher bills, and a blower motor working harder than it was designed to, which costs money all by itself.
High static pressure usually traces to undersized or insufficient return air, ducts that are too small or too long, crushed flex runs in the attic, a coil that’s dirty, or a filter that’s too restrictive. That last one catches good people all the time. A very high-efficiency filter in a duct system that wasn’t designed for the pressure drop can quietly choke the whole thing.
Refrigerant charge, measured properly
A system that’s low on charge still cools. It just cools poorly and runs forever doing it, which is exactly the profile of a high bill with no obvious failure. Undercharged systems are one of the most common causes I find of the “it works but it costs too much” complaint.
Charge isn’t checked by looking at a pressure gauge and calling it good. It’s checked by reading superheat or subcooling depending on the metering device, against the outdoor temperature and the manufacturer’s target. That’s the difference between knowing the charge is right and hoping it is.
And if a system is low, it leaked, because refrigerant isn’t consumed. So the correct response is finding the leak, not adding gas and scheduling a return visit next summer.
Overcharge matters too, for the opposite reason. Too much refrigerant raises head pressure and makes the compressor draw more current every minute it runs. That’s a bill problem with no comfort symptom at all, which is why it goes unnoticed for years.
Duct leakage, the one that gets expensive fastest
Now the big one for a lot of houses around here. Your ductwork runs through the attic. In a Cedar Hill summer that attic gets brutally hot, well past 130 degrees on a bad day.
Every leak in a supply duct dumps air you already paid to cool straight into that attic. Every leak in a return pulls 130-degree attic air into the system, which the equipment then has to cool before it can even start on the house. A duct system with meaningful leakage can lose a serious fraction of the system’s output before it ever reaches a room, and the homeowner has no way to see it. The house still cools, eventually. It just takes far longer and costs far more.
Along with leakage I look at insulation on the duct runs. Insulation that’s compressed, torn, fallen off a section, or was thin to begin with lets heat pour into the air through the duct wall for the entire length of the run.
What Cedar Hill houses do specifically
Cedar Hill earns its name. It’s the highest ground in the metroplex, wooded hills around Joe Pool Lake, and the terrain shapes the homes in ways that show up on a power bill.
The hillside multi-level builds are the first thing. A house on two or three levels has a natural stack effect, warm air rising to the top floor while the lower level stays cool, and a single-zone system that’s satisfied downstairs while the upper level is still hot will run and run trying to average it out. That’s a comfort complaint and a cost problem at once, and it’s frequently a zoning or duct-balancing conversation rather than an equipment problem.
The second is the trees. The wooded lots are a genuine asset for cooling load, real shade over a roof cuts the heat gain meaningfully, but they come with a steady rain of leaves and cottonwood onto the condenser. A coil that’s furred over can’t reject heat, head pressure climbs, the compressor draws more current, and the system runs longer to do the same work. It’s one of the highest-payback things I look at on a Cedar Hill call, and it’s the one item on this whole list a homeowner can genuinely fix themselves.
What you can measure this weekend
- Compare kilowatt-hours, not dollars, against the same month last year.
- Time a few cooling cycles on a hot afternoon and note whether the system ever satisfies and shuts off.
- Walk around the condenser and look at the fins. Clear the debris, cut back the vegetation, and rinse it gently with a hose from the outside in with the breaker off. No pressure washer.
- Put a hand at a few supply registers. Rooms that are noticeably weaker than others point at a duct problem in that run.
- Check the filter, and check what kind it is. If somebody upgraded to a very restrictive filter recently and the bill rose after, that’s a lead.
- Look at your thermostat’s schedule. A setback that got deleted or a fan setting left on ON instead of AUTO both add hours.
Where your part stops is anything requiring gauges, a manometer, or the electrical compartment. Static pressure, charge, and amp draw all need instruments and training, and the refrigerant circuit is under pressure. Do the outdoor cleaning and the observation, and leave the measuring to somebody with the tools.
The point of measuring first
The reason I go through all five of these instead of picking the likeliest one is that the fixes are wildly different in scale. A dirty coil and a low charge and a leaking duct system produce the same complaint on the same bill, and they cost very different amounts to correct. Finding out which one you actually have is the whole job.
Plenty of times the answer turns out to be the cheap end of that range, and I’m glad to deliver that news. What I won’t do is tell you a new system is the answer to a high bill before anybody has measured why the old one is working so hard.
You can read more about what we check on a full HVAC inspection, see everything we cover around town on the Cedar Hill service page, or look through recent work in the gallery. If you’d rather write it out, send us the details along with your usage numbers.
If your bill climbed and nothing looks wrong, call or text (214) 717-3959 to Book a Service Call, and I’ll measure your system instead of guessing at it.
