The Ideal Home For A Load Controller

Load controllers are great at saving energy but no one expects or wants to sacrifice their comfort to have one installed?  If they did, then no one would need a load controller and we would all just shut off our air conditioners during the hottest part of the day like our grandparents did before central heating and cooling.  The whole purpose of a load controller is to work behind the scenes, with little interference with our everyday lives.  What happens in some homes is that the friendly, non-assuming load controller who is supposed to save us money on our energy bills turns into this dominate, house controlling monster that everyone hates.  That’s when we get the call of, “just take it off my house!”

Of course, no one wants to get to that point so this guide will help you decide if a load controller is right for your home.  If you are considering solar or purchasing a load controller for your home, we’ve found that load controllers like certain types of homes… and if you’re one of the lucky ones that fit into its preference category, then we would give the thumbs up on installing one.  If you find your home doesn’t fit the load controller’s Type A fit, your home may still be compatible and benefit from a demand controller, it may just not be a match-made-in heaven.

What Are Load Controllers?

Load controllers or demand controllers are installed to save energy and are frequently required by utility companies when homeowners have solar panels installed.  Load controllers work by limiting the amount of energy used at one time by shutting down major appliances like the air conditioner, water heater, pool pump, dryer and oven.  Utilities companies like SRP are basically requiring all homes with solar panels installed, also have a load controller installed and APS utility companies is also encouraging homeowners whether they have solar power or not to use load controllers to control their energy consumption.  

What Homes Are Ideal For Load Controllers?

1.Slightly Oversized HVAC Systems

That’s right, we said it.  Even when writing this I still do a mental double-take because after all the soap box preaching we’ve done about the negative impacts of oversized air conditioners, our experience with load controllers on homes has been better when the air conditioner is about 10% oversized.  This doesn’t mean that a 5 ton unit gets put in place of a 4 ton system.  I recommend that if your HVAC system is border line now AND you are considering a load controller for your home, I would recommend you stay with the same size system you have now.

Use this table below to use as a guide to know if your HVAC system is oversized (the only true way to know what size AC your home needs is to do a Manual J load calculation). 

5 ton 1650 – 2000 sq ft
4 ton 1500 – 1600 sq ft
3.5 ton 1300 – 1450 sq ft
3 ton 1100 – 1250 sq ft
2.5 ton 900 – 1050 sq ft
2 ton 700 – 850 sq ft

If your home size fits and size of AC unit within these guidelines your AC system would qualify as “slightly oversized.”  Even though we have put oversized AC systems in a bad light before, using an oversized system with the strategy laid out can be an advantage. 

Why is having an oversized system a good thing?

A slightly oversized AC system (with the items below) will let you leverage super cooling much more effectively.  Super cooling is the ultimate way to game APS new rate plans and utility companies demand charge.  The loophole in APS’s new rate plans and in many utility companies demand based rate plans is that off-peak energy is ridiculously cheap… $0.05 per kWh compared to $0.14 per kWh with conventional rate plans.  With super a cheap off-peak rate plan E-27 for SRP customers and Saver Choice Max for APS customers,  you “super cool” your home during off peak hours to 72 degrees.  Then when peak-hours come from 10-2 pm for SRP or 3-8 pm for APS, you raise the thermostat up to 84 degrees.  With a well sealed home, your home’s temperature will never get about 80-82 degrees during the middle of the summer and your AC unit will never kick on. 

The problem with A/C’s that are sized just right for the house is that they aren’t designed to reach 72 degrees in the summer.  They can maybe get to 78 degrees during the heat of the summer and it will run constantly.  This isn’t a bad thing, it’s what A/C contractors are shooting for with a perfectly sized system (read why it’s important to size you’re A/C properly here).  With an oversized system, reaching a lower thermostat setpoint is easier and you’re beating APS at it’s own game by pre-cooling your home for pennies. 

Now if you have a slightly over-sized A/C system now but are not considering getting a load controller (see below for homes that would NOT be a good fit for a load controller), it’s best to size your system right and take advantage of what a properly sized A/C system can do for your comfort, your energy bills and your air quality.

​2. Have Good Insulation and Well Sealed Ductwork

​Having a well insulated attic and sealed ductwork also plays an essential role in the super-cooling strategy.  It’s important to keep all that cool air INSIDE your home once you’re A/C has done all that hard work.  If you’re home is leaking 30% of its air into the attic before it ever gets to your rooms and you’re insulation is below the rafters, all the cool air will leak out like when you first shut off your car A/C in a hot parking lot.  The ROI for putting more insulation and sealing the ductwork makes sense and we like to say that you are lowering your energy bills without raising the thermostat.

3. Programmable Thermostat

A programmable thermostat is not as essential as #1 and 2 are, but it sure makes life easier.  The ability to set-it-and-forget-it reduces the friction of having to remember when to adjust your thermostat each day.  Smart thermostats like Nest, Eco Bee or Lyric are not recommended with load controllers because of the 5 minute time delay after the thermostat has been turned off.  A regular programmable thermostat is the best option.

4. Single Story Home
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Why a single story home and why not a two story home?  A single story home has more attic area to add insulation to, whereas a two story home has more wall area that cannot have insulation added (it can, but it can be cost prohibitive).  Having more attic insulation will help keep all the super cooled air inside your home compared to a two story home which has great heat gains from less wall insulation and from the stack effect of warm air rising to the 2nd floor.  

What Homes Are Less Than Ideal For Load Controllers?

1. Smart Thermostats
Smart thermostats do not like load controllers because they are designed to have a continuous power supply.  When the load controller kills the power to the smart thermostats, it takes 5 minutes for the thermostat to reset itself.  This can conflict with the load controller calling for the AC to turn on and off during peak hours and lead to high temperature swings inside.  So when the load controller is calling for the A/C to turn on, the smart thermostat may still be in re-boot mode and unable to turn the system on. 
2. You Have An Air Conditioner That Was Properly Sized For Your Home, Or Slightly Undersized
A properly sized A/C system is good thing for so many reasons and I am not advocating to oversize your A/C system on purpose.  The ideal situation is if you’re A/C unit was recently installed so you’re not going to pay for a properly sized unit anytime soon (and it happens to be oversized).  However if your home did have a Manual J calculation done and your unit is properly sized a load controller may not be best for your home and here’s why: to use the super cooling strategy a properly sized AC system will likely not be able to take your home’s temperature past 76 degrees.  It’s simply too much load for your unit to handle.  Then when peak hours come during the hottest part of the day and you raise the thermostat up to 84 degrees, your homes’ temperature will rise much quicker from 76 degrees than from 72 degrees and you’re A/C system will likely turn on multiple times.  Will it be enough to still save money on your energy bills?  Yes, but not as much as the home sitting at 72 degrees.

3.You have an unpredictable schedule that lets you work from home some days
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To take full advantage of demand control (penalty) rate plans, the supercooling strategy is essential.  You need to be able to reliably, day after day, lower the thermostat during off-peak hours and then raise it during peak hours to take advantage of the utility company’s cheap off-peak energy rate.  If you are like me and sometimes work from home or have someone home on an irregular schedule then following the supercooling plan will be difficult to do because, of course we need to be comfortable in our own homes!

Breaking APS and SRP’s Rate Plans Down

For APS customers the rate plan you want to choose is the Saver Choice Max or Saver Choice Max Tech plan.  For SRP customers, it’s the E-27 plan.  Under these plans APS off-peak rate is only $0.052 per kWh compared to APS peak hourly rate of $0.087 per kWh plus a $17.44 per day demand fee, and SRP’s  off-peak rate is only $0.042 and $0.063 on-peak and with a demand charge of $9.59 for the first 3 kW and $17.82 for the next kW and $34.19 for each additional kW.  We’ve worked out the numbers and if you can avoid the daily demand charge, the savings is significant.  If you can’t avoid the demand charge, your energy bills are going the same or slightly higher!  That’s a huge difference, and that’s why it’s so important to be able to follow a set schedule.  

Homes That Should Avoid Having A Load Controller

1.Work from home, or you are at home during the summer afternoon

If you work from home, have a parent or spouse that spends their day at home, and then following the supercooling plan is harder to follow than if you are gone for work Monday through Friday on a regular schedule.

2.You “have to have the air set at 74 degrees all day”

I can’t blame those that are creatures of comfort.  I crossed the line at my house when I quietly turned up our thermostat one degree at a time during the summer to experiment our upper limit comfort levels and as my family was starting to sweat and get more uncomfortable each night my wife finally caught on and now get an earful anytime I want to touch the thermostat.  My wife now has total control of the thermostat and it pains me to have lost that battle.  She keeps the thermostat set between 76-78 in the summer now and I can’t do anything about it. Needless to say that I am not supercooling our home if she’s at home during the day and I my load controller is currently inactive.
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I would not recommend load controllers on your home if you have medical conditions that require your home be kept at a certain temperature or you run a day-care or nursing home from home.  There are other ways to save money on your energy bills, but a load controller probably wouldn’t be the best thing.