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How can I reduce my home cooling costs/energy usage?

BrettS

Active Member
Mar 28, 2017
2,155
2,575
Orlando, FL
So I realize this is pretty far off topic for this forum, but I know there are a lot of smart energy minded people here. If anyone has any suggests for other forums where this type of question would be more appropriate I’d be happy to hear them.

But anyway, I’ve been looking at the energy consumption of my heat pump and during the summer it’s running for as long as 15 hours a day. When it’s running it consumes about 2.2kWh, so that’s as much as 33kWh a day. Since my entire house only (not counting car charging) only consumes around 70kWh a day in the summer it looks like cooling is close to half of the energy consumption of my house and I’d like to try to reduce that if I can.

So far I’ve got three ideas, but I’m not sure which is really going to be the best use of my money and have the most impact.

I could replace my heat pump with a more efficient unit. The unit I have now is just a basic single speed/single stage heat pump, but it’s only about 6 years old and it is 14 SEER, so it’s not hugely inefficient. If I replaced it I’d want to go with a high end unit with a variable speed heat pump. I haven’t gotten any quotes, but from what I’ve seen online I’m probably looking at somewhere on the order of $10K for this. But I really have no idea just how much more efficient, say a 19 or 20 SEER variable speed heat pump would be. Would that save me 15kWh a day? Or 5kWh a day?

Alternately, I could replace my windows. This house has single pane aluminum frame windows. I can feel the heat coming in when the sun is shining through the windows on a bright sunny day. I did get a quote from a glass place to leave the frames and just replace the glass with double pane low E glass on all the windows for a bit less than $4000. That seems like a great price, but again, I’m having a hard time trying to figure out exactly how much that might save.

Finally I could add some insulation to my attic. This house was built in 2001 and I’m sure the insulation hasn’t been touched since then, so there could be some benefit to upgrading it. My utility company has a rebate for attic insulation and they suggest that the average cost after the rebate is about $300. That seems fairly reasonable, but again, it’s hard to quantify that into potential savings.

So, all that said, any ideas on what it might be best to focus my time and money on in terms of improving energy efficiency? Anything else that I didn’t mention that I should consider doing?
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
17,563
23,587
Riverside Co. CA
I just (as in 2 days ago) had a "whole house fan" put in my attic. The one I chose was from quiet cool, which happens to have its headquarters in the city I live in. I had no idea this would work as well as it does, here where I live. I dont think it would work nearly as well for you (or any other whole house fan, really) because the whole idea is to pull in "cooler outside air, in the early mornings or late evenings, to both cool you off, and push hot air out of the attic".

I dont think these work very well in humid areas, and I also dont think they work well in places where overnight temps dont cool down as much. I am certainly no expert, but if I were in your boat I would be looking at new windows, window coverings, and possibly doing an air leak evaluation test to see how much leakage I had in my home.

I am also planning on new insulation, because my home which was built in 2005, which I bought in 2013, also looks like the insulation hasnt been touched. I dont know how much that will help, but my particular goal is doing everything I can to get the heat out of the attic, because my home would feel like an oven in the evening.

The quietcool fan is already helping in that regard, and it has the added benefit of being, even at full speed, more than 4 times more efficient to run that one of the two A/C condensers I have.

Maybe look into a whole house fan, windows, and insulation before replacing the heat pump, which likely would have a pretty long ROI time frame if they cost as much as you mention.

Also, on a side note, at least to me, this type of post feels "on topic" since this section is about tesla energy (solar, powerwalls) and people evaluating that stuff are likely also looking into how to make their homes more efficient as they do so, so it doesnt feel too far off base to me at all.
 
I would bet the windows would be a significant improvement. Much older home (1940's), but for us replacing the original, single pane windows with double-pane windows (argon gas/low-E coating) made a big difference.

One thought would be to look into the home energy audits that some companies offer. I haven't done one myself, but I know our utility now offers a big discount on them (plus some incentives if you follow through on certain recommendations and lower your electric bill,) and they are supposed to cover a wide range of items and provide recommendations. It might give you harder numbers on the benefits of the various options you were talking about and find others you might have missed.
 
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Insulated windows are a scam (ok maybe high end triple pane but who is buying those?). I'm assuming you already have double pane, if not yes get those (just re-read your post, you have single pane you should replace them). Windows don't insulate well period. You'd get way more savings placing concrete awnings over your south facing windows so the sun doesn't heat the house in the Summer when the sun is high in the sky, but you'd still get all that sunshine heating your house in the Fall, Winter, and Spring. There is a book with a chapter about house design called "Rainwater Harvesting for Drylands and Beyond" that has excellent information.

Vent fans in humid climates introduce moisture into the attic which isn't a great idea, but yes I have one and it does reduce my cooling bill significantly.

I don't know the size of your house but a 2.2kWh draw is way better than running A/C units so I think you're doing pretty well.
 

BrettS

Active Member
Mar 28, 2017
2,155
2,575
Orlando, FL
I just (as in 2 days ago) had a "whole house fan" put in my attic. The one I chose was from quiet cool, which happens to have its headquarters in the city I live in. I had no idea this would work as well as it does, here where I live. I dont think it would work nearly as well for you (or any other whole house fan, really) because the whole idea is to pull in "cooler outside air, in the early mornings or late evenings, to both cool you off, and push hot air out of the attic".

If you have any gas appliances be careful with that whole house fan. I had one of those in my old house in NY state and we had problems CO2 alarms going off in the house occasionally. Eventually what we discovered was that if the whole house fan was running without enough windows in the house open it would draw air in through the water heater’s chimney and when the gas water heater ran it would essentially vent into the house and cause the CO2 levels to go way up.

I do think you’re right that it would be much less effective here in Florida though. It is quite humid here and in the middle of summer, even the early mornings and late evenings can be pretty warm.
 
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BrettS

Active Member
Mar 28, 2017
2,155
2,575
Orlando, FL
Insulated windows are a scam (ok maybe high end triple pane but who is buying those?). I'm assuming you already have double pane, if not yes get those (just re-read your post, you have single pane you should replace them).

Yeah, I feel like the single pane windows are definitely causing some heat gain in the summer. I also just found out that my utility offers a rebate for window upgrades as well. It looks like it might only be around $200, but hey, a $200 rebate is better than no rebate.
 

Uncle Paul

Well-Known Member
Nov 1, 2013
6,299
7,648
Canyon Lake,CA
Orlando is a hard place to achieve energy money savings because their electric costs are so low to begin with.

The Quiet Cool fans that work so fantastic in other parts of the country are not that effective there, because it really does not cool off all that much at night. Spring/Winter/Fall works best. Baking hot Summer you will still need to run your AC all night. It will give you some relief by venting your attic of the superheated air that continues to bake your house even after the Sun goes down.

Cost around $1,200. Side benefit is that it provides a nice breeze in the evenings. You must be home when it is on, because it only works when a screened window/door is open. Qualifies also for energy savings rebates as well.

Biggest help in Florida is Sun Control. Put shades over your windows or plant a shade tree on East and West sides. Keep the direct Sun from hitting your windows in the first place.

For my Lake House in California the Quiet Cool has reduced my AC use by over 80%. Run it when effective at night. Side benefit is that in the cooler Winter days I run it during the day to bring in the desired warmth and then don' t need to run my heater hardly at all. Big savings there as well. Works better in Califonia than in Florida because our energy costs are so much higher and the temperature swings are much greater, with nice cool evenings even after hot Sunny days. Do not confuse the Quiet Cool fans with the older whole house fans that sound like a helicopter running in your ceiling.

There was a joke about a customer that installed Thermal windows. Every time their bill for the windows came they just threw it in the trash. When the window company called them to ask why they were not making their payments they said they had no intention to make monthly payments because the sales person said "They will pay for themselves in 3 years" :)
 
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aesculus

Still Trying to Figure This All Out
May 31, 2015
5,017
2,922
Northern California
Some simple things:
  • Close any drapes and/or install window shades on sun exposed windows. We have them on all windows 365 because they insulate too
  • For those windows you still want to see out of go to the big box hardware store and purchase window film and install it.
  • Check you attic insulation. See what kind you have and what depth. Recommended Home Insulation R– Values | ENERGY STAR
  • If you are on TOU rates you can save a bit by pumping down the house to a cooler temp prior to peek rates and then raise it a few degrees at peek. You will need programmable thermostats for this
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
17,563
23,587
Riverside Co. CA
If you have any gas appliances be careful with that whole house fan. I had one of those in my old house in NY state and we had problems CO2 alarms going off in the house occasionally. Eventually what we discovered was that if the whole house fan was running without enough windows in the house open it would draw air in through the water heater’s chimney and when the gas water heater ran it would essentially vent into the house and cause the CO2 levels to go way up.

I do think you’re right that it would be much less effective here in Florida though. It is quite humid here and in the middle of summer, even the early mornings and late evenings can be pretty warm.

Thanks for the tip! My hot water heater is gas, but is in my garage. Its a standard 50 Gallon type, but brand new as my old one failed about 3 months ago. I should be ok since the water heater ( along with its venting) is in the garage, and the intake for my whole house fan is inside, in an upstairs hallway.

I have been careful to make sure I have windows open before I turn it on, however, but thanks for the tip, appreciate it.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
5,017
2,922
Northern California
If you have any gas appliances be careful with that whole house fan. I had one of those in my old house in NY state and we had problems CO2 alarms going off in the house occasionally. Eventually what we discovered was that if the whole house fan was running without enough windows in the house open it would draw air in through the water heater’s chimney and when the gas water heater ran it would essentially vent into the house and cause the CO2 levels to go way up.
Another Pro Tip that is not as safety critical but similar: Make sure that any sinks have been used in the last 30 days. If the sink traps dry out and you put a pretty good negative pressure on the house you will draw sewer gas into the house via the sinks. Just run some water through them for a minute or so if you smell anything from those sinks.
 
An interesting idea is to mist your condenser
with water so that the heat pump works much more effectively. I have considered this idea for my house. You’re looking at maybe $150.

The major consideration is the TDS, total dissolved solids, in whatever water you use. You don’t want to cake the condenser in mineral deposits.

Rain is free and has very low to no TDS and is therefore a good potential water source.

There are companies that make misters, very simple product. Just research the TDS factor.
 

Uncle Paul

Well-Known Member
Nov 1, 2013
6,299
7,648
Canyon Lake,CA
Thanks for the tip! My hot water heater is gas, but is in my garage. Its a standard 50 Gallon type, but brand new as my old one failed about 3 months ago. I should be ok since the water heater ( along with its venting) is in the garage, and the intake for my whole house fan is inside, in an upstairs hallway.

I have been careful to make sure I have windows open before I turn it on, however, but thanks for the tip, appreciate it.

Same thing with closing fireplace dampers. If you fail to open a window to allow the fan to vent, it will pull air down your flu and can blow ashes into your house.

I have a two story home, and usually open some upstairs windows first to evacuate all that hot air that collect upstairs and in the attic. Later, when going to bed I open a downstairs window and wake up to a supercooled house. Close all the doors and windows and the house stays quiet cool all the day long, as all the furniture, flooring and walls have been cooled and that mass continues to cool the area all day long.

Woke up this morning with thermostat indication 68º temps. Expect high today to be 92º and will not be needing to turn on the AC at all.
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
17,563
23,587
Riverside Co. CA
Same thing with closing fireplace dampers. If you fail to open a window to allow the fan to vent, it will pull air down your flu and can blow ashes into your house.

I have a two story home, and usually open some upstairs windows first to evacuate all that hot air that collect upstairs and in the attic. Later, when going to bed I open a downstairs window and wake up to a supercooled house. Close all the doors and windows and the house stays quiet cool all the day long, as all the furniture, flooring and walls have been cooled and that mass continues to cool the area all day long.

Woke up this morning with thermostat indication 68º temps. Expect high today to be 92º and will not be needing to turn on the AC at all.

Yeah, your location is pretty close to mine in fact. I am just south of you in temecula.
 

BrettS

Active Member
Mar 28, 2017
2,155
2,575
Orlando, FL
An interesting idea is to mist your condenser
with water so that the heat pump works much more effectively. I have considered this idea for my house. You’re looking at maybe $150.

The major consideration is the TDS, total dissolved solids, in whatever water you use. You don’t want to cake the condenser in mineral deposits.

Rain is free and has very low to no TDS and is therefore a good potential water source.

There are companies that make misters, very simple product. Just research the TDS factor.

I spent a little time investigating those at one point and my conclusion was that those misters are really more hype than substance. There’s the potential for mineral build up on the coil which could cause thousands of dollars of damage, all to save maybe $5 or $10 a month. Plus here in Florida where it’s quite humid they are much less effective as they rely on evaporation to provide their magical cooling abilities.
 

BrettS

Active Member
Mar 28, 2017
2,155
2,575
Orlando, FL
So as I’ve read through your suggestions here and done some of my own research I think I’m going to do the following:

My utility has a program where I can get a duct leak inspection for only $30. Since my ducts run through the attic I think it makes sense to do that.

As I mentioned above, they also have a rebate on attic insulation and it seems that it’s recommended for houses more than 15 years old, which this house is. They claim that after the rebate the cost should be somewhere around $300, so I figure I’ll get that done too.

Finally it looks like replacing my single pane windows with low e double pane windows makes sense as well, so I’ll go ahead and get that done too.

I’d love to get a high end HVAC system, but given that my system right now is only 6 years old and is already 14 SEER I feel like it’s hard to justify the cost for upgrading that. I think I’ll see how much the windows and insulation helps and then go from there.

Thanks again for all the thoughts and suggestions:)
 
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