Question about energy conservation

[Run_Amok]

I turned off the AC when I left the house at 1:15pm. It was 80° inside at that point.

I returned home at 4:45pm, and it was 85° inside.

Question: would it have been more efficient to have the AC maintain 80° over the 3.5 hours I was away, or for the unit to remain dormant and then work to cool the house down from 85° to 80°?

[Gator Bait]

You should not change the temp by more that 2-3 degrees. Research thermal mass. You aren't just cooling the air. The walls, furniture, everything contributes. You'll use more energy by letting it all get warm then recooling it. Spend the effort on not letting the cool air out and keeping your filter clean.

80*?? Helz with that...my warm temp is 72* while I'm away. 70* while home and up. 69* to sleep.

[POS Racing]

Yep what Gator said!

Heck this time of year if I let my house get up to 85 it wouldn't get back to my normal 78 until Monday morning.

Oh yea set some $$$ aside the next couple of months are big electric bill months due to the sweltering heat......

[Gator Bait]

Oh yet set some $$$ aside the next couple of months are big electric bill months due to the sweltering heat......

My bill typically ramps up to double normal late July, Aug, then settles late Sept. So far I've had a high of $310. I work from home most days so that 30* drop can add up a bit and I have a portable A/C unit cooling the garage to 78* b/c that's where the dog kennels are. But it wouldn't be that high if the wife didn't hold the daggun door open 20 times a day for the dogs to go in and out. At least she's learned to let her car cool before pulling it into the garage. That tip alone can save you some cash if you have an attached garage. That's a hella heat load you are pulling into the structure.

[gabkwong]

Well, I don't agree. Just think about why we use the programmable thermostat! Are they useless or waste of energy and $$? After I switch to a cheap basic programmable thermostat I saved more than enough $ to pay for the thermostat in the first month. If your A/C takes so long to cool the house and it is more 7 to 10 years old, you may want to looking into getting a new one. Being a TCB, I held out in replacing my more than 15 years old heat pump. Man, was I wrong and burning my $$$. After I replaced it 3 years ago, my summer electric bill went down by more than 30 to 40%!

If you are not in your house most of the day, you may want to investigate getting the supper smart thermostat, name starts with a "N", get the smartphone app and an OBDII reader (don't know the brand) to plug into your car. The OBDII reader will send signal to your smart phone when you start driving and the smartphone app know you GPS, it will than send command to your very smart thermostat to fire up your A/C to cool your house just in time for you to arrive. It will do the same, the opposite way, when you leave the house.

[Gator Bait]

Well, I don't agree. Just think about why we use the programmable thermostat! Are they useless or waste of energy and $$?

I use a programmable. With a net change of 3 degrees throughout the day. You can disagree all you want, but I doubt that will change the laws of physics. Thermodynamics are what they are. Now you can argue (and win) that if I shift my 3 degree range up 3-4 degrees I could greatly reduce my bill. But that shit ain't happening, Just like I'm not going to change out my 'old' 12 seer AC to get a new 14-16 seer AC. My unit is in good repair and I invest in and practice efficiencies in keeping the house cool, vs cooling the house (insulation, reduced air loss). I also don't start dropping my air down towards my sleeping temp until the sun is setting. Trying to drop temps during the max heat load of day is also inefficient. ...you know...when most people are driving home and that fancy super smart controller the glossy flier convinced you was the bees knees and key to green living and AC Nirvana.

Any chance you might be interested in buying a bridge?

[Run_Amok]

Sorry for the absence - reconnecting at work after the move has been all-encompassing.

Thank you all for the advice / experience / insight - I do appreciate your time. That said, both viewpoints appear to be valid and therefore I am slightly more confused. Lol.

I searched for info on conservation, and most of the energy companies recommend a programmable thermostat; however, they do not specify a range of degrees to stay within nor do they say to program the unit to kill the HVAC completely during certain hours. In essence there is not direction on how to actually realize the benefits of a programmable.

Any further thoughts?

[sammm]

^I have used a programmable thermostat for years and it will save you money. Just don't go crazy and program in huge temp swings...3-5 degrees is all I will do, but
every little bit helps!

Also go check out www.powertochoose.org/ and find a reasonable Kwh rate.

[Robert]

Also go check out www.powertochoose.org/ and find a reasonable Kwh rate.

Yep, I got jacked for years (I know my fault) before I went there.

Just be sure and read the terms for the real price, a lot of them are tricky on the list price.

[Gator Bait]

Just be sure and read the terms for the real price, a lot of them are tricky on the list price.

Watch out for minimums. Most of the cheaper ones I saw the min was higher than my average usage.

[tailchaser]

... the supper smart thermostat, name starts with a "N"...

I wish my Nest would cook me supper...

I started using Trieagle energy... They charge a flat $4.95 + whatever their advertised kwh rate is + about .9% in taxes. During the summer, they tend to have 1 to periods per billing cycle lasting 60-120 minutes where if you use less than your usual kwh, they credit you back at about $.50-$1.20 per kwh... The net is that my actual payment per kwh tends to be about $.08 over the course of a year, which is less than anything else I'd tried by over a penny. They may not be the cheapest, but they seem to be the most honest. If you decide to give them a try, PM me for my account number to use to sign up, and I'll give you 2 years of forum supporter status when the credit hits my bill.

[HudsonHawk]

The best thing you can do is spend on sealing air leaks, insulation and upgrading to an efficient AC unit. We replacesd our cheap builder grade POS units with high efficiency Lennox units. Not only did we save about 50% on energy bills, but we went from barely being able to get the house down to 80 to where it will maintain 70 all day long with 100+ outside temps.

[motorollow]

Watch out for minimums. Most of the cheaper ones I saw the min was higher than my average usage.

I told the wife to keep it as cold as she wants so we don't go below the minimum!

[HudsonHawk]

Another thing would be to add solar screens to reduce solar radiation through the windows.

[Gator Bait]

Another thing would be to add solar screens to reduce solar radiation through the windows.

Those made a significant difference on a previous older house. This one has good Low-E windows that in direct summer sun feel cool on the inside. Also if building, building on 2X6 studs allows for more insulation. Might not be an option for some of those McMansions around DFW, but for our cottage I was glad for the choice.

If trees are an option a good shade tree can both save the earth and your bills. Planting an adult tree isn't cheep, but the immediate benefits are worth it IMO.

[Gator Bait]

I searched for info on conservation, and most of the energy companies recommend a programmable thermostat; however, they do not specify a range of degrees to stay within nor do they say to program the unit to kill the HVAC completely during certain hours. In essence there is not direction on how to actually realize the benefits of a programmable.

Any further thoughts?

I found a few Government sites that specified both the the temp and the amount of swing. They said 78* in the summer and 8*'s warmer when away. I take that with a grain of salt since they (the government) work from a one size fits all model and always have a political leaning in their recommendations. Having grown up in far south Louisiana with no AC in our home or school, I won't be purposely uncomfortable now. Wife must have been chilly while watching TV last night and hit the hold on the AC at 73*. I woke up at 2a hot. Hell with that...'Run Program' and drop to 69* FTW!!

[Run_Amok]

^I have used a programmable thermostat for years and it will save you money. Just don't go crazy and program in huge temp swings...3-5 degrees is all I will do, but
every little bit helps!

Also go check out www.powertochoose.org/ and find a reasonable Kwh rate.

I am hoping someone could share a math formula or calculator that shows how much energy is expended to cool a house from 85° to 80° vs maintaining 80° over a 4 hour period.

Thank you for the link - I checked it out and I found that I **may** be paying 20% - 30% more than the cheapest option listed on that site (I am with Green Mountain). Derp. I should have shopped around.

Yep, I got jacked for years (I know my fault) before I went there.

Just be sure and read the terms for the real price, a lot of them are tricky on the list price.

Watch out for minimums. Most of the cheaper ones I saw the min was higher than my average usage.

I told the wife to keep it as cold as she wants so we don't go below the minimum!

Thanks for the info, guys.

I wish my Nest would cook me supper...

I started using Trieagle energy... They charge a flat $4.95 + whatever their advertised kwh rate is + about .9% in taxes. During the summer, they tend to have 1 to periods per billing cycle lasting 60-120 minutes where if you use less than your usual kwh, they credit you back at about $.50-$1.20 per kwh... The net is that my actual payment per kwh tends to be about $.08 over the course of a year, which is less than anything else I'd tried by over a penny. They may not be the cheapest, but they seem to be the most honest. If you decide to give them a try, PM me for my account number to use to sign up, and I'll give you 2 years of forum supporter status when the credit hits my bill.

Unfortunately I am already in a 12-month contract with Green Mountain. If I remember next year I will most certainly get you the referral reward.

I will call them and see of there is anything they can do to lower my rate so that I don't feel like I'm being gouged. I am okay with paying a lil more for green energy, but if I am paying 30% more, well then that sucks.

The best thing you can do is spend on sealing air leaks, insulation and upgrading to an efficient AC unit. We replacesd our cheap builder grade POS units with high efficiency Lennox units. Not only did we save about 50% on energy bills, but we went from barely being able to get the house down to 80 to where it will maintain 70 all day long with 100+ outside temps.

How many months to recoup the cost of the new Lennox units? The peace that comes with knowing your AC is not going to give up the ghost from exertion is priceless.

Another thing would be to add solar screens to reduce solar radiation through the windows.

Done! They seem to help!

Those made a significant difference on a previous older house. This one has good Low-E windows that in direct summer sun feel cool on the inside. Also if building, building on 2X6 studs allows for more insulation. Might not be an option for some of those McMansions around DFW, but for our cottage I was glad for the choice.

If trees are an option a good shade tree can both save the earth and your bills. Planting an adult tree isn't cheep, but the immediate benefits are worth it IMO.

Thanks! What are your / everyone's thoughts on radiant barriers for the underside of the roof?

I found a few Government sites that specified both the the temp and the amount of swing. They said 78* in the summer and 8*'s warmer when away. I take that with a grain of salt since they (the government) work from a one size fits all model and always have a political leaning in their recommendations. Having grown up in far south Louisiana with no AC in our home or school, I won't be purposely uncomfortable now. Wife must have been chilly while watching TV last night and hit the hold on the AC at 73*. I woke up at 2a hot. Hell with that...'Run Program' and drop to 69* FTW!!

Back in 2008 we went through a period of having nothing. By the Lord's grace we came out of it intact, albeit with a post-Great Depression level of austerity. We became disciplined in how we manage resources, careful to turn off lights, devices, etc. and adjust the HVAC to avoid (perceived?) waste. So, in a nutshell, a programmable will automate something that is a part of my daily routine.

In DFW after spending a few hours in 100° weather, coming home to 85° is almost doable. 80° is a good balance of comfort and cost-saving. 78° is almost sanctuary-like :)

Thanks again everyone for your help!

[OZMDD]

There is no simple formula for what you want, as every house is full of unique variables.

[Gator Bait]

It's certainly about personal choices. We bought a 1600 sqft well insulated one story home for its efficiency and then cool/heat it to our personal comfort. But we only need room for us and the dogs.

We have a metal roof with radiant barrier between it and the wood. The wood doesn't get nearly as hot as my old shingle home w/o radiant barrier. Apples and oranges though...

[tailchaser]

Just for giggles, I'll share the numbers for July/August for my 2500 sf two story (gas heat and water) that we keep at 78 in the evening, 76 for sleeping, and drift to about 80 during the day when we're not home (about 3º higher upstairs, as we're not up there much right now). June was $100, July was $150, and August is on track for about $185. All lighting was updated last year (save 2 exterior lights that are rarely on). My winter electric bills were mostly within a stone's throw of $30.