What’s The Average Electric Bill To Cool My Apartment?
Hunting for a new apartment in Houston, TX? One thing you want to know is how much it costs to run an air conditioner. It seems a straight forward question, right? There’s plenty of exhaustive DOE reports on the average Houston home’s electricity usage. But why is there dang-near-nada reliable information on how much air conditioning an apartment in Houston costs?
The key problem is that the Department of Energy and the Energy Information Agency only collect information on “residential” over-all usage by combining data from both houses and apartments. So, it takes time and persistence just to tease out useful apartment over-all usage information. And depending on who’s doing the teasing, you might wind up with the wrong information that’s out of date by a decade ago or more.
None of that is much help if you’ve got a paper thin budget and you’re looking to move before electric rates in Texas start climbing later this summer. You want to see how much it will cost you in today’s money, not what it cost in 2010 or 2015. You need realistic and reliable numbers to help you estimate costs while you search websites for a new place. So, let’s dig deep to find you the right kind of information to help you make some reasonable estimates about how much air conditioning will cost you in your next Texas apartment. Plus, we’ll check out things you can do to reduce your AC costs once you move in.
Apartment Summer Electricity Costs
First, let’s start with figuring out the average size of a Houston apartment. While you might not find a perfectly-average “average sized” apartment, it’s useful to start with a common size to compare with. Apartment size varies regionally due partly by climate and by market. Nationally, the average apartment size is 889 square feet. That’s close to what we’re looking for since in the average Houston apartment is about 879 sq. ft.
Building age should also figure prominently into the equation when you compare and shop. Home sizes (both house and apartments) have been on the increase for decades. Square footage for apartments (nationally) increased by 2.1% between 2009 and 2015. That might not sound like much but on average between 2009 and 2015, newer units had an average of 40 square feet more. However, the significant point is that since newer apartments tend to be larger, they require more energy for air conditioning to be cooled. So while you might be able to afford renting a newer and bigger place, you should double check how much it will cost you to heat and cool it. Of course, older, smaller apartments may be equipped with old central AC systems. And while they might work fine, their old and inefficient design might end up costing you as much as you would have spent for a newer apartment.
How Much AC Per Square Foot?
If you ask any HVAC technician worth their salt, they’ll likely say that you can’t accurately calculate AC demand per square foot. Now, that’s very true. However, many will cite a “rule of thumb” that, while terribly inaccurate for planning and installing a system, will provide a ball park figure to estimate your cooling costs.
The rule of thumb for air conditioning is 500 square feet per ton (12,000 BTUs) equals the size of air conditioner needed. This rule can include other important sizing considerations like the number of residents, how shaded the building is, number of windows, whether there is a kitchen, and ceiling height. However, for our apartment-hunting purposes, we don’t need to get that specific just yet. For now, we only need the ratio of 500 square feet per ton as a quick, crude estimation for energy cost.
AC Sizing Matters
First we need to determine how many BTUs per hour it will take to cool our average Houston apartment. That’s done using the 500 square feet per ton (12,000 BTUs) ratio:
879/500 x 12,000 = 21,096 BTUs of cooling capacity per hour.
In practice, our Rule of Thumb equation runs into a technical problem. Most residential air conditioning systems are sized in increments of half a ton (6,000 BTU/hour) sizes:
12,000 BTUs = 1 ton
18,000 BTUs = 1.5 tons
24,000 BTUs = 2 tons
That means the average apartment’s AC system will sized to the nearest half ton. That choice or going up or down depends on who designed the system and when. If a system was designed 30 years ago, it might be both inefficient and undersized for the current climate. If it’s oversized, it might waste energy and needlessly increase your Houston electricity bill.
For our average-sized apartment, the nearest half ton is 18,000 BTUs.
So, if 1 BTU = 0.000293071 kWh, then the BTUs of capacity per hour converts into kWh this way:
18,000 x 0.000293071 kWh = 5.2752793 kWh
How Many kWh to Cool An Apartment?
Now, “kWh of capacity” means you need to have an AC unit that can use up to 5.27 kWh. It doesn’t mean you’ll actually use that much. The important point in figuring AC usage is that the l o n g e r your AC must run to match your thermostat’s temperature setting, the more Texas electricity you will use. The more you use, the more it costs you.
In mid-autumn and early spring, you probably won’t run the AC very much at all. In winter, even if you’re using electric heat, that amount won’t likely won’t be anywhere nearly as high your summer AC energy consumption. That said, even though there’s times it sure seems like it, air conditioners don’t always run nonstop, 24 hours a day, 7 days a week. So, let’s assume that your apartment’s AC unit uses 5 kWh and that for the whole month of July, your AC ran 8 hours/day.
- That’s 8 hours x 5 kWh = 40 kWh per day.
- At 30 days x 40 kWh = 1200 kWh.
If we assume 10 cents per kWh, then it costs $120 just for the Houston electricity supply to run your AC for 8 hours each day for 30 days. For 10 hours per day, the total goes up to $150.
Other Apartment AC Factors
An apartment’s description might look perfect on a website but you should visit the unit before you sign a lease. That’s because with these figures in mind, it’s important to see how many of all those other factors mentioned earlier that might affect your air conditioning usage:
- How high are the ceilings? Apartment square footage doesn’t include ceiling heights. And the higher the ceiling the larger the space that needs cooling.
- Is the apartment in the middle or on the end of the building. Units in the middle of a building are insulated by their neighbors. Units on the ends will have at least two exterior walls.
- How many south-facing windows are there?
- What is the age and condition of the building?
- Are there window and door drafts
- What is the type of AC system? Central air, split system, or less efficient room units.
Reduce Your Apartment’s AC Costs
The most efficient ways to reduce your apartment’s air conditioning costs is to reduce the amount of time it runs The best way to control run time is to adjust your thermostat to 7°-10°F higher for 8 hours a day when you’re not at home or asleep. Programmable thermostats do this very well because you can set up the temperature to change in advance automatically. That way, your apartment will be at a comfortable temperature when you arrive or are active. This can save 10% per year.
Another important thing is to keep the AC air filters clean. Dirty air filters reduce air flow and make your AC run longer.
Lower the Apartment Heat Load
All buildings absorb heat from the sun during the day. Luckily there are simple ways to reduce how much heat your apartment absorbs. Keeping out the heat will cut your costs to keep your place cool:
Use drapes to close off windows where the sun shines in. Blocking off sunlight with medium-colored draperies with white-plastic backings can reduce heat gain by 33%.
Be on the look out for drafty doors and windows. Hot, humid air leaking into your apartment from outside adds to heat to your apartment. Weather stripping is cheap and easy to apply. Why wait for your landlord to take care of it when drafts are adding to your Houston electricity bill . Not sure which kind to use? Energy.gov’s Weatherstripping page has THE BEST guide for selecting the right one for your apartment.
Like to cook? Try using other ways to cook by using the microwave or grilling outside. Thinking about baking in the oven? Avoid it but if you really must, try to do it well after the sun has gone down. Turn off the AC and use a fan to blow the heat from your kitchen outside. This also applies to running the dishwasher or any other appliance that creates a lot of heat.
One final way to cut your apartment air conditioning costs in Houston is to shop the best electricity rates at http://www.texaselectricityratings.com. Not only can you find competitive rates for different term lengths but also customer written reviews on 135 retail electricity providers. We make it quick and easy to help you find the best plan for your needs.