High summer temperatures in Texas mean running your air conditioner longer, especially in areas of the state liable to run up 90-degree plus temperatures for weeks on end. The air conditioner is a crucial – and in some cases life-saving – appliance for making it through the sweltering summer months. However, all that cool air means you’re going to use a lot of electricity, which can take a nasty bite out of your paycheck. Read on to learn more about how high temperatures can run up your electric bill, and what you can keep to keep cooling costs from getting out of hand.
How Much Does Temperature Affect Your Electric Bill?
High temperatures inevitably mean high cooling bills, a lesson you’ve no doubt experienced first-hand. There’s no way around it. Let’s say you’ve set your AC at 72°F on a 90° day. Because of the heat, your system is running frequently, which means you’re using a lot of electricity: around 3,500 watts per hour for a three-ton central air unit. While it probably won’t be running continuously, on a hot day the AC might run 15 hours out of 24, consuming 52.5 kWh per day.
If your air conditioner needs to maintain that load for the entirety of July or August, it could consume in the neighborhood of 1,500 kWh in a single month. If your electricity rate is a relatively low $.10 per kWh, that means you’re still shelling out $150 for air conditioning alone, before you even take into account the rest of your electric appliances.
How Supply and Demand Plays Into Your Electric Rates
But that’s not all. The Texas electricity market buys and sells energy according to wholesale prices, which fluctuate based on supply and demand. On hot days, everyone wants electricity, so prices will rise. Complicating this are transmission lines that only handle so much power transmission, especially during hot weather. In areas where there’s not enough transmission capacity but demand is high, congestion can add additional costs onto the price of the electricity, and sometimes even result in blackouts or brownouts. You can watch these prices change for your local area in real time.
If you’re on a variable-rate plan, you’ll see those wholesale price fluctuations and spikes reflected in your monthly bill. If you’re on a fixed-rate plan, you won’t see any change over the course of a month, but you may experience increases later on depending on how badly the spiking wholesale prices affected your energy provider.
How to Avoid High Energy Costs During Extreme Weather
If you’re savvy about your home habits, you can reduce the cooling load on your air conditioner even as the suffocating heat settles in for the summer, and thus keep your bills down to a reasonable level. The most cost-effective cooling strategies for cooling your home during a heat wave are those that prevent indoor heat from building up in the first place.
You can start your efficiency initiative by using daily temperature fluctuations to your advantage. Summer heat doesn’t begin building from the overnight low until 7 am. Between 10 am and noon, heating accelerates, usually approaching a peak at 3 pm. All the while, your home will absorb and retain heat through heat transfer, conduction and radiant heating, then gradually release it through the night.
Adjust Your Habits
You can reduce your home’s heat gain during the day with simple things like blocking the sun with treatments on south and west facing windows. For example, highly reflective blinds can reduce heat gain by around 45 percent, while white-plastic-backed drapes can reduce heat gain by 33 percent.
Avoid adding more to your home’s cooling load by waiting until evening to use heat-intensive appliances such as ovens, stove tops, dishwashers, washing machines and dryers.
Reduce Your Home’s Humidity
Texas is also famous for high humidity. The warmer the ambient temperature, the more water the air can hold, which increases relative humidity (RH). That’s why 50 percent RH at 74°F feels comfortable while 50 percent RH at 85°F or 95°F feels sticky. Water vapor also holds heat energy.
An air conditioner’s cooling coil works by pulling heat out of the air that contacts it, and most initial cooling goes to reducing the humidity in your home. That’s because when humid air hits the cooling coils, the water condenses and gives up its heat energy to the coil. The higher the humidity in your home, the longer it will take for the system to reduce the air temperature because all that heat energy must be released from the humid air first.
You can make your air conditioner’s job easier by using ventilation fans to blow moist, humid air outdoors after you shower. Don’t leave these fans running for too long, however, as most residential vent fans can clear a bathroom of steam in ten minutes. Read more on how to control your home’s humidity with this guide.
Use Ceiling Fans
Speaking of fans, while box fans and ceiling fans don’t actually cool your home, their breeze helps your body cool itself through the natural process of perspiration. That’s why it feels about 4 to 6 degrees cooler to sit under a ceiling fan. Just remember to turn the fan off when you leave the room.
Raise Your Thermostat
To really save energy on your air conditioner usage, you need to raise the thermostat by 5 to 10 degrees — or more — when you leave to go to work or during the night when you’re asleep. The savings get better if you have a programmable thermostat so you never forget to make the adjustments. If you have a smart thermostat you can get even more options and data on how to manage temperature settings more efficiently.
When the thermostat is turned up a few notches, not only does it take less effort for your air conditioner to meet the target temperature, you also slow down the loss of cool air, which will reduce your AC’s workload even further. According to Newton’s Law of Cooling, an object’s rate of temperature change is proportional to the difference between its own temperature and the ambient temperature. Basically, heat energy moves towards cold.
Reduce the Burden on Your Air Conditioner
In summer, that means heat moves from outside to inside. As inside and outside temperatures approach equilibrium, the rate of heat conduction slows. Let’s say your thermostat is set to 74F when you are home and the outside temperature is 90F. That’s a 16 degree difference. But if you raise your thermostat to 80F before leaving for the day, then it’s only a 10 degree difference and the rate of temperature change will be lower.
It’s true that if you raise your settings during an eight-hour work day and then lower them upon your return, your AC may run for a while to bring the temperature to your at-home setting. However, it won’t use as much energy use compared to keeping your home’s temperature 6 degrees cooler for an entire eight-hour period or longer. That 6 degrees of extra cooling can add 36 percent more to your energy usage, at a rough rate of 6 percent per degree.
Plus, even though the temperature in your home might be higher while you’re away, the system still should run often enough to keep the humidity in your home low — and in Texas, that’s half the battle.