Air Conditioning Efficiency & Dehumidification
Updated: Aug 28, 2019
Welcome to the #1 Katy, Texas Air Conditioning Blog. This blog post is primarily intended for the greater Katy, Texas area.
Air conditioning concerns can differ greatly from one area to the next namely because of differences in season length, humidity concerns and in some cases the lack of humidity in certain areas of the country that pose different challenges.
There are some people who prefer it warmer than others we're all unique in that way. Air conditioning was more or less invented to make your home more comfortable. What does comfort mean to you?
The purpose of this Air Conditioning Blog post is to inform you of options or if you prefer: choices that are available to help make your home the oasis of comfort you would like it to be. Comfort means something to you and it likely means something else to a few other people you know. So now that you have some understanding behind this topic of air conditioning I can share some misconceptions with you in terms of efficiency.
When people (most people) hear the term efficiency they relate this to money. How much less money they will spend in operating something. It's the old buy something too cheap, and pay an abundance in operational costs. This can happen, but there's more to it than that. The trade off is what do you give up for the efficiency part of the equation.
I'll use a few analogies to help you understand this efficiency situation better. I'll start with the car analogy. You have a truck that burns gas at 1 gallon for every 10 miles you drive. You also have a car that gets 30 miles for every 1 gallon. The car is more efficient than the truck, because it gets 3 times the mileage for the same amount of gas. But what do you give up for that efficiency? The truck can haul much more stuff than a car can. So if you do a lot of hauling of things in the truck the efficiency of the car isn't going to make the difference you think it will. The design of the truck is for a purpose that makes a car with better efficiency not worth the gain in efficiency because of the purpose the truck was designed for. (To haul stuff / if you don't haul stuff --- the truck is very inefficient.)
Efficiency in heating systems for the home is another example in efficiency and it not meaning what you think it means. An electric furnace (new or old) is 100% efficient while most gas furnaces (for the Katy area) are only 80% efficient. When talking of electric furnaces for every BTU of heat created, 1 BTU of energy is used. That's efficient! 1 BTU in = 1 BTU out.
An 80% gas furnace by comparison is inefficient, because 80% of the gas burned is used to heat the home, 20% of this heat goes up the flue as waste by products. That's inefficient. But did you know that the electric furnace heating bills cost you more than the gas furnace equivalent? Why?
Because gas is cheaper than electric rates. This is why efficiency doesn't always mean less operation costs. Just realize that an electric furnace paired with a heat pump for our climate in Katy, Texas will probably give a 80% gas system a run for it's money in terms of the cost of operation. So just because you have an electric furnace doesn't mean you can't reduce that operational cost of the electric furnace and still be quite comfortable from a cheaper operation cost stand point. (Operation costs are what it costs you monthly to operate your HVAC equipment.)
When Efficiency Means What You Think It Does
Manufacturer's are required by law to make air conditioner's and furnaces energy efficient. Now that you understand the nuances of such that I mentioned above I will discuss things in this section that relate to better performance and lower utility bills.
SEER is an acronym for Seasonal Energy Efficiency Ratio. The higher this number is for the AC equipment in question the better or cheaper it will cost you to operate the system (*provided it is installed properly). By law in the Katy area, no AC system can be installed that is less than 14 SEER as of 2016, this may change at some point in the future. This type of AC equipment is considered 'entry level' equipment.
If comfort as well as dehumidification doesn't mean as much to you, then a 14 SEER single speed AC may be all you ever need. As an example: if you set temperatures higher like 78 or 80 most of the time in your home. The Katy, Texas area design temperature is 75 degrees indoors. So if you set the thermostat higher than that point the cost of a higher energy efficient HVAC system is probably above what you truly need.
In other words to actually gain any real efficiency you have to be running the equipment more. If you run the equipment less there is no sense paying for higher cost AC equipment. The more energy efficient the equipment, the more the equipment will cost. This cost can be off set because it's more efficient to operate which when done properly can reduce your light bill. If you are replacing an older HVAC system it could be as much as $100 a month or more in operational savings.
AC Comfort Level
If in order for you to be comfortable in your home you run the thermostat lower than 75 for the Katy, Texas area climate. It will probably be advantageous for you to install a higher efficient AC system. Currently air conditioning systems can be up to 21 SEER energy efficient. These types of high efficiency AC systems are best considered if you have no plans of selling the home. You probably will not recoup the cost unless you are in a more luxury area of the real estate market and home buyers are seeking such systems in the homes they are considering. Most of the time having a higher end system may help you sell the home faster, outside of that the advantage in it is the comfort it provides your home.
2 Speed AC Systems
These are often mid range efficiency systems that deliver some dehumidification above that of a single speed AC system. However, dehumidification features can be particularly challenging for the Katy, Texas area. It is not uncommon for our area to have high humidity all year long some years. Because humidity can be high at nearly any temperature a 2 speed system is easy to find fault with it's short comings within a year or two of being installed during parts of the year where humidity remains high and temperatures are lower.
The manufactures of such systems use lingo designed to fool you up front to thinking this dehumidification feature is more than it actually is. Certainly a 2 speed system is better than a single speed when trying to tackle humidity related concerns during summer time running of the AC system. However, once the shoulder seasons for the Katy, Texas area come around it will become abundantly clear the limits a 2 speed AC system has in terms of controlling high humidity in the home. I try explain these things to you up front to inform you better of what to expect from such a HVAC system.
Variable Speed AC Systems
Variable speed AC systems take things like dehumidification and energy efficiency to a whole new level. With that said, one HVAC brand within this category can be entirely different than another in the number of speeds it's actually allowed to run in as well as the controls needed to operate it. This is why you 'should' rely on someone like me. While the operation is similar the differences lie within the controls of the system and or limits that those controls impose. Meaning that while some AC systems are variable speed they are limited to the number of stages they run in. In addition to that, they may require proprietary controls to operate them. Proprietary controls will limit your choices in various ways as well as cost more.
This seems to be changing, because as time goes on newer products with different designs have come to our air conditioning market. It's hard to say just how this will turn out exactly. This blog topic was written in June 2019 with final edit August 28, 2019.
What Exactly Is A Variable Speed AC System?
For the most part a variable AC system is one that is driven by DC voltage or direct current. Where as most AC systems use alternating current or regular incoming line voltage from the utility pole. The variable AC takes that alternating current and converts it DC or direct current. From there a bunch of different things can occur depending on the design of the air conditioning system. Another advantage to a variable speed AC is that it is extremely quiet in low speed operation and most of the time it will run in those lower speeds.
Myth: variable speed AC systems take longer to cool.
Wrong. It takes them time to ramp up to full capacity typically this will occur within a few minutes. If the home is under a heavy heat load any AC system will take time to pull the heat out of the home. Depending on how hot it is outside, how hot it is inside it could take upwards of 4 hours to cool down regardless if the AC system is variable speed, 2 speed or regular single speed AC. There is no such thing as 'instant' cooling for the home comfort market. It works by scientific principles, not magic.
How Efficiencies Are Achieved With Variable Speed AC Systems
When fan motors and especially compressor motors are run from DC voltage then efficiencies in the operation of those motors can be achieved. There is far less amperage on start up and because these motors are designed to be variable the speeds in which they are able to operate are only dictated by the controls they are attached to.
If you are able to reduce the speed of a motor what happens? The result is less amperage or current needed to run the motor. This ultimately reduces the current draw and the amount of energy you use. This is how you pay less on your utility bill in terms of operational costs to run the equipment. Certainly another way is to shop for a cheaper utility rate. But shopping for a cheaper electric rate now doesn't mean a cheaper rate in the future.
If your AC system has a compressor that can modulate from 20% capacity up to 110% of capacity what does that really mean? Because the system has this ability means that it only provides the amount cooling you need while also keeping the system running for longer periods that will reduce humidity as well. Dehumidification does not occur if the AC system is off. Which is why a single speed air conditioner will not achieve the kind of dehumidification you would want for a climate like Katy, Texas because a single speed air conditioner is always cycling on and off.
What Is A Heat Load?
Did you know that your air conditioner is designed to handle a heat load? Your air conditioner does not produce cooling. It removes heat from the structure. This heat load varies depending on a number of factors that also vary, the heat load in your home is constantly changing. The heat outdoors, the heat indoors, the number of people in the structure, the insulation or lack thereof among other factors can all impact how well (or not so well) your air conditioner achieves the cooling you desire for your home.
Cool air is not really cool... it's just air with the heat removed. We condition the air, by removing the heat. If we also reduce the humidity within the structure at the same time, you will even feel that much more comfortable. How cool is that?
Dehumidification Challenges For Your Home
When your air conditioner is running it also provides some dehumidification. However, all single speed air conditioners are designed to drop temperature not control humidity. Dehumidification is a huge challenge for the Katy, Texas area.
Did you know that if I installed HVAC equipment that dropped the humidity in your home a mere 5% you would be that much more comfortable than just merely dropping temperature alone? People with high humidity in the home often complain that their AC system is too small. They claim the AC system they have doesn't provide enough cooling. Did you know that only increasing the capacity of an AC system for our area in Katy, Texas will make the humidity problem in your home even worse! This will not make you comfortable and it could make you sick. (Mold growth could occur.)
Why? Because an AC is turned on by temperature and shut off by temperature. Over sizing the AC system (capacity, not physical size of the unit!) will shut the unit off even quicker and will ultimately provide less dehumidification. That will not end well.
Over cooling is not dehumidification. You must select the right tool for the job. Design of the HVAC system is critical. Equipment selection is a part of system design. This is why you use a pro like me. You will always need a good AC repairman, no matter who you select to perform the work, what brand you choose and other comfort options you chose for your home. All brands break, all brands need maintenance. I do my best to minimize these kinds of problems.
Whole Home Dehumidifier
Whole home dehumidifiers do exist to combat humidity concerns in the home. However, they come at a cost. There is no free lunch when it comes to dehumidification. You have to understand these machines are separate from your air conditioning and heating system, even though they are attached via duct work to your existing HVAC system.
They require room near your HVAC equipment and require a dedicated electrical circuit for operation as well as condensate water draining. If the home is larger it may require more than one whole home dehumidifier. It is another system that will need maintenance, repair and at some point it will have to be replaced. Those costs never go away, if you select this type of option.
Operational costs could be as high as $30 to $50 a month on your electric bill to run a single whole home dehumidifier in addition to air conditioning, lighting and other electrical usage. How much a whole home dehumidifier will cost from a operational stand point will depend on dehumidification set points you choose and how much humidity you actually have in the home as well as how much your electric rate is.
Certainly there are smaller units that you could buy and place in various spots in the home, but these are often limited in capacity (how much humidity they actually remove) and you have to remember to empty the condensate pan yourself. Where as the whole home dehumidifier is set up with separate controls and condensate is drained to a suitable location without you having to think about it.
Home Dehumidification Conclusion
Humidity control for your home in Katy, Texas poses unique challenges. Technology in the way of variable speed AC systems give the best bang for the buck in terms of equipment needed to help handle this arduous task in the most efficient way possible, that if done properly reduces your electric bill and provides you with better home comfort.
Because a variable AC system is capable of modulating compressor speeds and reducing electricity draw as well as reducing compressor off times will lead to higher dehumidification with less over cooling and because you also need cooling for our climate as well it's more cost effective to have one machine to perform both tasks. (Cooling & Dehumidification)
Remember equipment selection is just as important as system design in nearly all cases. How this AC equipment operates can have a large impact on how much better dehumidification will be during times of the year in which we still have high humidity to contend with, but also lower temperatures. Variable speed AC systems are still driven by temperature which can pose problems when humidity is high and temperatures are cool. Given a variable speed air conditioner's ability to start low and ramp high, it is my belief these problems will be minimal at best.
Thanks for visiting with me today, I hope your day is crisp and comfortable.
About the author of the #1 Katy, Texas Air Conditioning blog:
My name is Ray Austin. I am the owner and operator of Austin Air Companie, a HVAC Service Company serving Katy, Texas | Cypress, Texas | Richmond, Texas and some surrounding areas. I am a Texas Licensed HVAC Contractor with 24 years experience in Air Conditioning and Heating Systems as of July 2019. I hold an AOS degree in HVAC/R, EPA universally certified to handle any refrigerant and NATE certified in HVAC installations and repairs.
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