energy usage calculation for home cooling

[KrisZ]

That seems like a big delta for the A/C to deal with. If you can ramp it up more slowly that would be better for the unit. I am pretty frugal but even I keep it at 75 or below when we are home. My Wife would revolt at 77.

It's actually better for the unit. It's the cycling that kills the compressor and the fan motor. Temperature delta has nothing to with how "hord" the unit works. It work the same regardless, but what changes is the time it stays on. By having a fairly large delta between the inside temp and set temp, you ensure the unit works continuously for a much longer period of time without any cycling. This in turn is easier on the unit and dehumidifies the house much more effectively.

 

[alarmguy]

It's actually better for the unit. It's the cycling that kills the compressor and the fan motor. Temperature delta has nothing to with how "hord" the unit works. It work the same regardless, but what changes is the time it stays on. By having a fairly large delta between the inside temp and set temp, you ensure the unit works continuously for a much longer period of time without any cycling. This in turn is easier on the unit and dehumidifies the house much more effectively.

Yes, this is what I thought to be true too. I was thinking any device starting and stopping creates wear and tear. Even an automobile, constantly cruising along at 55 mph vs stop and go city traffic, local errands, stop start etc/

 

[KrisZ]

Yes, this is what I thought to be true too. I was thinking any device starting and stopping creates wear and tear. Even an automobile, constantly cruising along at 55 mph vs stop and go city traffic, local errands, stop start etc/

It's actually worse with electric motors because they go from 0 to 100% in less than a second. Cars don't go full throttle at each intersection.
The startup current can be 5-6 times higher than the running current. They require a massive amount of amperage to start up, all of which creates wear and tear.

edit:
I'm actually thinking of installing a soft start in my system, since it's a heat pump and works pretty much all year round. It reduces the startup current significantly, plus my backup generator will be able to start it up with it installed.

 

[QwikKota]

It's actually better for the unit. It's the cycling that kills the compressor and the fan motor. Temperature delta has nothing to with how "hord" the unit works. It work the same regardless, but what changes is the time it stays on. By having a fairly large delta between the inside temp and set temp, you ensure the unit works continuously for a much longer period of time without any cycling. This in turn is easier on the unit and dehumidifies the house much more effectively.

Short cycling due to oversized condensing unit is definitely bad for the unit and humidity but running a single speed unit for several hours without any cool down time can't be a good thing. I have a variable speed unit that runs all day during the peak months but it runs in low until a drop in temp is forced by the t-stat. It can barely be heard when running in low.

 

[alarmguy]

It's actually worse with electric motors because they go from 0 to 100% in less than a second. Cars don't go full throttle at each intersection.
The startup current can be 5-6 times higher than the running current. They require a massive amount of amperage to start up, all of which creates wear and tear.

edit:
I'm actually thinking of installing a soft start in my system, since it's a heat pump and works pretty much all year round. It reduces the startup current significantly, plus my backup generator will be able to start it up with it installed.

ahh,, I have seen soft start mentioned a few times. Always curious but need facts to read up on and not marketing from those companies ... I havent thought too deeply about it. I do know about the start up current and part the reason for capacitors too. Throw in the fan and blower motors on top of it. Big exception for me is I dont have a generator.

 

[KrisZ]

ahh,, I have seen soft start mentioned a few times. Always curious but need facts to read up on and not marketing from those companies ... I havent thought too deeply about it. I do know about the start up current and part the reason for capacitors too. Throw in the fan and blower motors on top of it. Big exception for me is I dont have a generator.

They do work and reduce the startup amperage significantly. Here is a good video going over the installation with amp measurements before and after.
What I still need to verify is if these units are reliable and can last 5-10 years without trouble. It's hard to find credible data on that.

 

[KrisZ]

Short cycling due to oversized condensing unit is definitely bad for the unit and humidity but running a single speed unit for several hours without any cool down time can't be a good thing. I have a variable speed unit that runs all day during the peak months but it runs in low until a drop in temp is forced by the t-stat. It can barely be heard when running in low.

No disrespect, but that's your uneducated feelings. These things car run 24/7 non stop all year round, if they need to. No cool time is required, otherwise it would've been built into the unit's programming, just like compressor delay is, for example.
Also, during really hot days, the unit may run for 45 minutes and be off for 15 minutes or 10 minutes or even less. Do you really think it will significantly cool down in a 95F-100F temps during this short period of time?

It's like saying you cannot drive across America non-stop and need to give the engine a cool off time. It makes no sense.

 

[jghall00]

The free nights are a bit frustrating on my Chariot Energy plan since it is 11pm to 6am. If it were 10am to 7am to more closely match our sleep schedule, it would be awesome.

I think the plans have gotten more restrictive over the past 12 months due to growing demand, perhaps from data center construction. Mine runs from 8PM till 6AM. Not sure what I'll wind up with when I renew next spring.

 

[QwikKota]

No disrespect, but that's your uneducated feelings. These things car run 24/7 non stop all year round, if they need to. No cool time is required, otherwise it would've been built into the unit's programming, just like compressor delay is, for example.
Also, during really hot days, the unit may run for 45 minutes and be off for 15 minutes or 10 minutes or even less. Do you really think it will significantly cool down in a 95F-100F temps during this short period of time?

It's like saying you cannot drive across America non-stop and need to give the engine a cool off time. It makes no sense.

A properly sized unit will only run all day on the hottest day per the local climate when talking extremes. To state a condensing unit can run at 100% duty cycle year round and it will last the same length of time as one that cycles makes no sense. We are talking residential units, not commercial units.

 

[KrisZ]

A properly sized unit will only run all day on the hottest day per the local climate when talking extremes. To state a condensing unit can run at 100% duty cycle year round and it will last the same length of time as one that cycles makes no sense. We are talking residential units, not commercial units.

Again, what's your reasoning besides feelings? Plenty of commercial applications use regular residential units if the load requires 5 tons or less. The only reason units are sized to run almost a whole day on the hottest day is to prevent short cycling during normal temperatures. That's part of sizing the unit properly, nothing to do with it's longevity.

I think you're assuming that these units get hotter and hotter as they operate, hence your flawed assumption that they need to cool off. Nothing of this sort is happening. The motors will achieve a temperature equilibrium where the unit's temperature will remain steady. This is thermodynamics 101 and is part of the design criteria. The fan motor is cooled by the air that the fan is pushing around it and the compressor is cooled directly by the refrigerant.

And yes, a continuously running unit will last longer than a cycling one. The starting amperage of these units can be 120-160 amps, whereas the continuous running amps are usually 15-25 amps. It's a massive difference in power draw and heat generated. You simply don't realize how much power and strain is required to start up these motors. Couple that with overcoming the static mechanical resistance of the bearings and magnetic windings at startup and it actually does make sense, to those that understand some engineering and physics.

Not sure if you ever seen a unit that short cycles, but that's when the motors and the compressors get really hot. That almost never happens on a continuously running unit, unless the bearings seize due to water contamination and/or rust. Otherwise they stay cool as long as they run.

 

[QwikKota]

Again, what's your reasoning besides feelings? Plenty of commercial applications use regular residential units if the load requires 5 tons or less. The only reason units are sized to run almost a whole day on the hottest day is to prevent short cycling during normal temperatures. That's part of sizing the unit properly, nothing to do with it's longevity.

I think you're assuming that these units get hotter and hotter as they operate, hence your flawed assumption that they need to cool off. Nothing of this sort is happening. The motors will achieve a temperature equilibrium where the unit's temperature will remain steady. This is thermodynamics 101 and is part of the design criteria. The fan motor is cooled by the air that the fan is pushing around it and the compressor is cooled directly by the refrigerant.

And yes, a continuously running unit will last longer than a cycling one. The starting amperage of these units can be 120-160 amps, whereas the continuous running amps are usually 15-25 amps. It's a massive difference in power draw and heat generated. You simply don't realize how much power and strain is required to start up these motors. Couple that with overcoming the static mechanical resistance of the bearings and magnetic windings at startup and it actually does make sense, to those that understand some engineering and physics.

Not sure if you ever seen a unit that short cycles, but that's when the motors and the compressors get really hot. That almost never happens on a continuously running unit, unless the bearings seize due to water contamination and/or rust. Otherwise they stay cool as long as they run.

Aside from being rude you are also hyperfocused on the compressor. There are many other rotational components in the system that don't last forever when running constantly. I have replaced several blower motors and condensing unit fans over the years. These can not only keep the system from working they can also allow the compressor to fail without heat removal.

 

[alarmguy]

For clarity, I understand the discussion going on between short cycling and not.
I have none of those problems. The system is amazingly matched to the house, as even told to me by the refrigeration outfit that was installing the systems for the production builder who has so far in the last three years put up just guessing 200 homes.

Anyway, he told me when I was concerned about constant running and hot temperatures that my concerns were unwarranted.
The house is methodically matched to the unit size taken into account wall insulation, attic, insulation, windows, and possibly exposure and foundation. I can’t remember.

He said to oversize a unit along the coast would end up with damp, humid, clammy conditions in the home, as well as the danger of mold forming.

I made that call when I initially moved in and now living here going on three years I can say the unit is properly matched. It doesn’t cycle on and off frequently it runs long enough where the inside of our house is nice and dry. It is true around 100° and humid. The system is hitting its maximum where if you set the thermostat way high, it will take a long time to bring the temperature down on a 95+ degree day.
Thinking about that isn’t bad because it also keeps the house dry on those days.
In my mind, I still wonder if a 2.5 ton unit instead of a 2 ton unit would’ve been better in our 1800 square-foot home but then in another high-end community I took the serial numbers off of the unit they were installing on custom 2250 size homes and those were 2.5 ton units.

Bottom line I have no idea why I’m posting this other than the thermostat shifting I got going on. I think it’s gonna work out great as far as even between the two opposing posts taking place by you guys because pretty much the unit shuts off at 8 AM and turns on at 6 PM getting a full off time and not needing to cycle at the hottest point of the day. Then running efficiently even if for a longer constant time when outside temperatures are up to 20° cooler.
Still even then, the temperature is stepped, as posted in previous posts.

I do have to say I have a fair amount of experience with refrigeration units, let’s just say I owned a high-end grocery store, with maybe up to a dozen different compressors. Some built-in display cases. But most were remote with air cooled and water cooled compressors in the basement up to the refrigeration cases.
As I learned about them, I was adjusting the controls myself. The remote units don’t work on temperature. It’s based on high and low pressure in the lines.

Sounding like a win-win to me if I could get away with this in the heat of the middle of the summer. Right now hitting 87° during the day outside sounds hot but the late afternoon evening ocean breeze is cooler this time of year because it’s cooler ocean water.

One interesting notice I have a family member about 8 miles away from me, slightly different size home in the sense that it has a cathedral ceiling but same living square footage. That house was built 20 years before this one which has newer building standards that house has a 3 ton unit.

 

[KrisZ]

@alarmguy don’t worry about the system, your HVAC guy was spot and and it will last just as long as any other, maybe even longer since it sounds like it’s sized just about perfect. Long run times are good for these units. I don’t feel like explaining it any further, but you seem to get it. Others can think whatever they like, it has no impact on me.

 

[andrew_j]

Paste your post into ChatGPT and maybe it will be give an answer or you prompt to get an answer your like

 

[PandaBear]

My advice is spend your though thinking about how to improve your live and income, so you can spend the money making your AC comfortable instead of saving $3 a day.

The closest I have done is to get a small window AC that help boost my undersized central AC, and target cooling in the particular room with direct sun light while keeping the central AC off. I don't look at the time of use, if I want AC I turn it on because I hate heat.

 

[alarmguy]

My advice is spend your though thinking about how to improve your live and income, so you can spend the money making your AC comfortable instead of saving $3 a day.

The closest I have done is to get a small window AC that help boost my undersized central AC, and target cooling in the particular room with direct sun light while keeping the central AC off. I don't look at the time of use, if I want AC I turn it on because I hate heat.

Wow! what a nasty reply, thanks but no thanks. Clearly you dont get the reasoning nor thought process.

 

[alarmguy]

@alarmguy don’t worry about the system, your HVAC guy was spot and and it will last just as long as any other, maybe even longer since it sounds like it’s sized just about perfect. Long run times are good for these units. ...

Yes, I suspect longer lasting just as my programming in our last much bigger home with two units still running strong 19 years, even for the new buyers of that home. Different program with that home, one unit for each floor, depended on heat vs cooling. I used cold air sinking and hot air rising to my advantage. It was an open house with 16 foot ceilings in the main living and foyer area. So air easily moved between upper and lower floors with no narrow staircase. Actually makes it a little tricky and how I ended up using that open space to program the two units.

I think what I am doing will maximize this unit too. Assuming my OP is correct. In reality the run time is (so far) only in the cool of the night) when it is more efficient because the outdoor temps are 20 degrees cooler, less stop and start too.
Hot Daytime, (so far) the unit doesn't have to run at all and no cycling on and off. Only makes sense less wear and tear. The unit will actually run much less I think over all without having to "fight" the hot daytime outdoor temperatures.

I'LL POST THE RUN TIME once I get through June of 2026 so I can compare to June of 2025. Of course I will also have the kWh's used too.
I can also pull up week by week but with variables in weather month will be most accurate. I might post middle of June because I will have about 4 weeks of run time to compare to last year.

Thanks for your comments. I know I am on the right track. Im disappointed from someone I respect in here regarding the comment to me to improve my life and not worry about saving $3 a day. Where the heck did that come from? Got me! But I too am not going to go out of my way to prove anything. I always looked to this forum as a way to brainstorm ideas, not get life advice or price to someone I live better than them. Kind of weird, a forum about EVs, oils, solar panels, etc etc to maximize efficiency and longitivtiy somehow turns it into something else.

 

[tbm5690]

I'm relocating to eastern AL in about a month, now under contract on our new home there. I'll be curious to see how cooling costs look in the dead of summer. House is a 3,000 sq.ft. ranch that was built in 2024 with spray foam insulation for walls and roof. I'm going to have to take all that I know about living in ND and throw it out the window. @alarmguy I'll need some southern grass yard and landscaping tips as all I know is how to maintain a good Kentucky Blue turf in growing zone 3

 

[jghall00]

I'm relocating to eastern AL in about a month, now under contract on our new home there. I'll be curious to see how cooling costs look in the dead of summer.

You'll be running HVAC most of the year to control humidity. If there's a smart meter it may have consumption history from the utility.

 

[alarmguy]

I'm relocating to eastern AL in about a month, now under contract on our new home there. I'll be curious to see how cooling costs look in the dead of summer. House is a 3,000 sq.ft. ranch that was built in 2024 with spray foam insulation for walls and roof. I'm going to have to take all that I know about living in ND and throw it out the window. @alarmguy I'll need some southern grass yard and landscaping tips as all I know is how to maintain a good Kentucky Blue turf in growing zone 3

Well, I think you are going to be good with your electric costs. Though we are all different and you will have different plans to chose from. If you choose the peak use plan I see the cost is 7.9 cents kWh for 20 hours during summer and 21 hours during winter. $8 kWh during peak times of 4 hours summer and 3 hours winter. Or you can go standard roughly 14 cents kWh 24 hours a day.
Sprayed foam insulation, that is like WOW. I think you will be amazed. I was in real estate at one point in my life. You could walk in the attic of huge homes mid sumner and be amazed how cool they can be compared to a typical attic. The homes are more quiet too. Such as airplanes etc.

No matter what grass is at the home, you want only one kind. Zoysia grass. Best part is that is doesn't matter what grass the home currently has. in 2006 (we sold it in 2022) we bought new near Lake Murray SC. Builder landscaped with Bermuda grass. Looked good but PITA with bugs, fungus, and thatch. So I bought 3 x 3 inch Zoysia plugs and with sticking a shovel into the existing grass, no digging I just spread the existing grass apart and stuck the plugs into the ground packing them down with my feet. Zoysia over time will crowd out and take over most any grass all the time while still having a normal lawn as it takes over. Anyway, within a couple years, the Zoysia took over all the Bermuda grass at our house, completely, none left. People (not kidding) would knock on our door at time to ask what we do to our lawn. When selling the house it seemed like part of the conversation all the time.

So here is something timely, 100% TRUE, our new home 2023 we have one of the nicest builder landscaped Centipede lawns in the community, NC coastal area. Some thing, compliments all the time and questions on what I do. However just YESTERDAY I received my first order of 64 - 3 x 3 inch zoysia plugs (8- trays, containing 8- 3x3 inch plugs). and put them in the lawn, over a couple years, it will be he same thing, a superior zoysia lawn even though our lawn looks beautiful, to me, nothing comes close to Zoysia. Best part is you do not have to disturb your existing lawn if you do not want to. Just plant 3 inch Zoysia plugs into your existing lawn. If that existing lawn is on good shape plant them maybe 5 feet apart and in a few years you will be good. If in a rush, plant according to instructions, more like 1 foot. Or if you really want to spend and there is no grass now, have Zoysia sod installed (expensive)
After that, give any brand lawn food every 6 weeks or so during the warm season and you will never have to do anything else to the lawn. I actually fertilize my lawn every 4 to 5 weeks, warm season. Heat of summer 6 weeks.

Just do a search for Zoysia 3 x 3 inch plugs. You will see TONS of sites and resellers for the smaller 1 or 2 inch plugs. I choose only 3 x 3 , selection is more limited but I like a nice robust larger plug since I want to to start spreading as fast as possible.
I always ordered from "SeedRanch" in Florida for my last home and I also ordered them for my son's home. They were always reliable stand up company. Which I did again for this house. However this time even though I ordered from them the plugs actually came from a company called SodPods (maybe that is a subsidiary of theirs I dont know) When ordering I did not really care too much which variety I was going to get. Always very happy. Years back it may have been Meyers or Empire Zoysia. This time I was surprised to see they shipped one I never heard of. ICON Zoysia. I looked into it, not as popular because it is newer hybrid from an Australia. Anyway, I think I am going to be happy with it from what I read. Pretty much they are all good, the only ones I wouldn't want are the ones advertised as thin blade. But Meyers and Empire are solid. I am hoping (and suspect I will be right) The ICON will be too. If you do a search, chances are if you want what I did (and my son) you want 3 x 3 inch plugs, your choice will be limited with 3x3 and just go with it.

Anyway, took only less then 2 hours to put in 64 plugs and I have 64 more ordered. This time I ordered direct from the company that sent them instead of ordering from SeedRanch.com Still Seed Ranch is an upstanding company. By mistake somehow my order a couple weeks ago never arrived at our new home, I called, a real person picked up. Seems they were delivered to my old address. They sent a new shipment to my new address no charge.

This time I ordered another 64 plugs direct from the company that sent them https://trysodpods.com/ (company is bethelfarms.com)
Once I get them, I I'll be done and slowly will take over my existing lawn.
Photos below are what received yesterday and just planted the same day.

This is 8 trays 2 rows of 4 = 64 plugs