A higher-than-usual energy bill is one of the most common reasons homeowners call me. Sometimes the cause is obvious. Often it is not. The good news is that HVAC issues account for most of the spikes I see, and many of them have straightforward explanations.
Before you call anyone, here is how to figure out whether your heating or cooling system is to blame and what to check on your own.
Start With the Pattern
Your energy bill tells a story if you know how to read it.
Compare your current bill to the same month last year. A 15 to 20 percent increase without a major lifestyle change usually means something has gotten less efficient. If the spike only happens during the heating season (November through March in Kelso and Longview) or the cooling season (July through September), that points directly at your HVAC system rather than your water heater, lighting, or other appliances.
A gradual rise over two or three years is also worth paying attention to. HVAC systems lose efficiency at roughly 3 to 4 percent per year as they age. A system that is 10 years old may be running 30 to 40 percent less efficiently than it did when it was new, and you might not notice because the change has been so slow.
Sudden spikes are different. Those usually point to a specific problem that developed recently: a refrigerant leak, a clogged filter, a failing component.
The HVAC System’s Share of Your Bill
Your heating and cooling system accounts for 40 to 50 percent of your home’s total energy use. Heating alone can represent 42 percent of your monthly bill during winter. That makes it the single largest consumer in most homes, which is why it is almost always worth investigating first when bills go up.
The Most Common HVAC Causes
Dirty Air Filter
This is the first thing to check, every time. A clogged filter forces your system to work harder to pull air through, increasing energy use by up to 15 percent according to the Department of Energy. It also stresses the equipment.
Filters should be replaced every one to three months depending on the type and how much the system runs. If you cannot remember the last time you changed yours, start here before anything else.
Dirty Coils
The coils in your HVAC system are how heat gets transferred in and out of your home. When they get coated with dust and debris, they lose the ability to do that efficiently. Research from the EPA found that even a thin layer of dirt on condenser coils, about a millimeter, causes a 21 percent drop in efficiency. More significant fouling can push that to 35 percent or higher.
Coil cleaning is part of a standard annual tune-up. If your system has not been serviced in a while, this is often where a meaningful chunk of efficiency has gone.
Duct Leaks
The EPA estimates that typical homes lose 20 to 30 percent of conditioned air through leaks, gaps, and poorly connected sections of ductwork. In some homes the number is higher.
When your ducts leak, your system has to run longer to compensate. You are paying to condition air that never reaches the rooms it is meant to heat or cool. If your bills are high and certain rooms in your home feel uncomfortable compared to others, duct leakage is worth investigating.
Duct sealing is not a glamorous fix, but it is one of the most cost-effective improvements you can make to a home’s efficiency.
Low Refrigerant
Your heat pump or air conditioner relies on refrigerant to move heat. When the charge drops due to a leak, the system works much harder to achieve the same result. A 25 percent undercharge reduces efficiency by about 16 percent and adds roughly $100 per year per ton of system capacity to your operating costs. At 60 percent undercharge the system can barely function.
Signs of low refrigerant include: the system running constantly without reaching the set temperature, ice forming on the lines or outdoor unit, and warm air coming from vents when cooling mode is active.
Refrigerant does not get “used up.” If your charge is low, you have a leak that needs to be found and fixed before more refrigerant is added.
Aging Equipment
Every heating and cooling system loses efficiency over time. The degradation rate averages about 3.7 percent per year, and it accelerates as components wear. A heat pump that was installed more than 10 years ago may have lost a significant portion of its rated efficiency, even if it still runs.
This is why older systems that are “still working” can still be costing you more than they should. Sometimes repair makes sense. Sometimes replacement pays for itself in energy savings within a few years, especially with current rebates available through Cowlitz PUD and Washington State’s HEAR program.
Wrong Size Equipment
An oversized system short-cycles: it blasts on, quickly reaches the thermostat set point, and shuts off before completing a full conditioning cycle. This is inefficient and leaves humidity problems behind. An undersized system runs constantly without fully reaching the set temperature.
Both conditions drive up energy bills. If your system is relatively new but bills are still high, sizing may have been done incorrectly during installation.
What You Can Check Yourself
Before calling a technician, run through these in order:
Thermostat: Make sure it is set to the right mode (heat or cool, not just fan), set to AUTO rather than ON, and responding when you change the temperature. Replace batteries if applicable.
Air filter: Pull it out and look at it. If it is gray and clogged with debris, replace it. A clean filter costs a few dollars and takes two minutes.
Outdoor unit: Walk outside and look at the condenser. It should have at least two feet of clearance on all sides. Clear away leaves, grass clippings, or anything that has accumulated around it. If the coil fins look visibly dirty, a gentle rinse with a garden hose (spray from inside out) can help.
Breakers: Locate the two breakers for your HVAC in your electrical panel. If either is tripped, reset it once. If it trips again immediately, stop and call someone: that indicates an electrical fault that needs to be diagnosed, not reset repeatedly.
Condensate drain: Find the PVC drain line that exits near your indoor air handler. Pouring a cup of white vinegar down it once a month prevents the algae buildup that can clog the drain and trigger a safety shutoff.
When to Stop and Call
Stop doing your own investigation and call a professional if:
- The system is not reaching the set temperature despite a clean filter and clear outdoor unit
- You see ice on the refrigerant lines or coils
- There is a gas smell anywhere near the system
- A breaker trips again after being reset
- The system will not turn on at all despite correct thermostat settings
- You hear grinding, banging, or screeching sounds that were not there before
Any of those symptoms points to something that needs a technician, not a homeowner with a flashlight.
One More Thing Worth Knowing
If you have been putting off a diagnostic because of the cost, my current diagnostic fee is $49.99. That covers a full system inspection and a clear explanation of what I find. If you decide to move forward with a repair, the diagnostic fee applies toward the work.
I serve Kelso, Longview, Kalama, Castle Rock, Woodland, and the surrounding area.