Tesla Powerwall without solar ?

[NW-Bound]

As mentioned, it pays to know how much you use, in order to see how much you can cut back in the case of electric outage.

In my case, in the 30 years living at this address, I have had only one significant outage that lasted 4 hours, and it was due to a substation failure. I do not count short outages of a few seconds that were apparently caused when they were doing some power switching.

I was interested in the power usage when I was building and testing out my DIY solar system, and wanted to know how much of a dent it would make of my power bill.

And I found some interesting numbers, such as the 24-kWh/day minimum usage. I found that the main 32-c.f. fridge draws 4.8 kWh/day, while the smaller 26-c.f. fridge draws 1.6 kWh/day. The large fridge gets opened several times a day, and we use tons of ice out of it. The smaller fridge gets opened once or twice a day at most. I guess that just to keep the fridges going plus some minimal lighting plus the basic router+laptop usage will require 8-10 kWh/day.

My solar system has been cranking out 25 to 45 kWh/day, depending on the season. And I am still tweaking it.

 

[NW-Bound]

That’s interesting, thanks for posting. When I did the calculations for our system I think the payback rate was about 10 yrs, but I assumed pretty minimal price hikes in electricity, which hasn’t been the case. When we looked into the Tesla system, the cost to install was very expensive vs traditional batteries, but I’ll admit we just wanted to get our system in ASAP, so we didn’t spend as much time as I would have liked researching options.

Yes, Tesla system installation cost can be high, as I gather from the info found on the Web. They also have a backlog, and do not serve some areas at all.

I am not interested in having one installed, because I can DIY for cheaper and for fun. However, I am curious about this industry, and have been watching out for developments. I know that many other companies also offer competitive systems. However, they are not cheap either, and usually do not have the clean look of the Powerwalls.

 

[NW-Bound]

One more thing about the Tesla Powerwalls or any other battery storage systems: their power output can be more limited than you think.

Central ACs have a huge inrush current demand when they start. It is usually 5X the normal run-time current drawn. This means that my 5-ton central AC which draws 4-5 kW when running needs 20-25 kW to start.

A Powerwall 2 can handle the peak surge of 7 kW. Two of them combined will provide 14 kW of surge power. That's not enough for a central AC.

And even if you can start the AC, at 4 kW drain, each of the Powerwall will provide 3 hours of run time each. You would need a bank of them, maybe 10 in a row?

In the usual installation, the Powerwalls are wired such that they will not provide power to heavy appliances such as ACs, water heaters, cloth dryers, ovens, etc...

I cannot power the central AC with my DIY solar either. I installed 2 minisplits, so that I can make use of my off-grid solar system. The minisplits are of the DC inverter type, and they start up gently under electronic control.

 

[Koolau]

An installation with 2 Powerwall units would probably keep our house going for 6 days, according to Tesla:Even if you think that's overly optimistic, it would probably do for at least 2-3 with mostly normal usage, or maybe closer to 24 hours if it was ridiculously hot and we were running the whole house AC compressor. That's not too bad, IMO. As I said, a generator might be best for those who experience long outages, like those at the end of the infrastructure. A battery system would probably be optimal for those who have frequent but brief interruptions or dips in power.

In my mom's case, I'm sure she would have been more than satisfied with just running the forced-air furnace and the fridge plus a lamp or two. Of course, about 10 days is a long time. So Powerwall might have worked but no idea of the cost. A small Generac IS affordable though I don't have the numbers (just going by the couple of folks I know that have one.) YMMV

 

[skipro33]

One more thing about the Tesla Powerwalls or any other battery storage systems: their power output can be more limited than you think.

Central ACs have a huge inrush current demand when they start. It is usually 5X the normal run-time current drawn. This means that my 5-ton central AC which draws 4-5 kW when running needs 20-25 kW to start.

A Powerwall 2 can handle the peak surge of 7 kW. Two of them combined will provide 14 kW of surge power. That's not enough for a central AC.

And even if you can start the AC, at 4 kW drain, each of the Powerwall will provide 3 hours of run time each. You would need a bank of them, maybe 10 in a row?

In the usual installation, the Powerwalls are wired such that they will not provide power to heavy appliances such as ACs, water heaters, cloth dryers, ovens, etc...

I cannot power the central AC with my DIY solar either. I installed 2 minisplits, so that I can make use of my off-grid solar system. The minisplits are of the DC inverter type, and they start up gently under electronic control.

When I built my house, I designed it so the guest quarters are on one side with it's own AC system. There are two AC units each are rated at 2 tons each. Do you think 2 Powerwalls could handle a single 2 ton unit with the other phantom powers? My typical phantom power is around 300 watts and when I run my generator, that has a watt load meter on it, it reads right around 3000 watts, maybe a little more. If I kick on both AC units it reads a little over 5000watts load. Also, I set up the AC this way because all 'portable' generators are limited to 30amps due to their built in breakers and wire gauge. A 4 ton and higher unit uses more than 30amps so a full sized home generator, along with it's cost, would be needed. I got away with a 7kw Honda inverter generator I bought used for $1,500, converted it to propane and plumbed the house's 500 gallon propane tank to it's location.
BTW, I'm getting the 2 Tesla power walls via 'Grid Resiliency' program funded by the California PUC and based on Medical Base Line utility rate and located in an area where power shut offs due to high fire danger are common. Cost is $26,400 installed. I have to fund to get the install, but am rebated the full amount after permission to operate is granted by the utility company, usually about 3 months to obtain.

 

[Offgrid Organic Farmer]

Every home in my township has at least one generator.

It is common to see two generators. One large unit and one small unit.

The small generators can power lighting and PCs. The small unit sips a gallon of fuel every 8 hours.

The big generators allow you to flush toilets, run laundry, and refrigerators & freezers, and to take showers. Those big units guzzle a gallon of fuel an hour.

Those homes run the big unit for one-hour each day, as they do laundry, take showers flush toilets, and bring the temps of freezers back down to appropriate temps.

In this manner, you consume the least amount of fuel. One hour each day running a big generator and 23 hours of running a small generator, means that you only consume 11 gallons each day tops. If you shut down the small one when you sleep, you can consume even less.

Nobody here has A/C, and most homes here burn firewood for heating.

One of our neighbors is a gunsmith. His insurance company insisted that he install a big generac to power his machine shop and security system. He regularly goes through $150 in fuel each month.

I have lived here for 15 years so far. During the past 15 years, our power company has never been capable of providing power for one-month continuously. Every month our power will go out at least once.

Just how it works here in rural areas of the East Coast.

 

[Starsky]

I see no real reason to have one without solar. There are a lot more efficient emergency power supplies. The savings in off-peak electricity would also be very hard to justify.

The one interesting capability that this potentially offers is the ability of the power grid to store energy offline and pull from the batteries if needed; thus avoiding the need for costly and polluting backup generation. It would require everyone to have one though... Eventually it might even make sense for the power company to provide subsidized units to each user to be used as a redundant piece of the smart energy grid.

 

[NW-Bound]

When I built my house, I designed it so the guest quarters are on one side with it's own AC system. There are two AC units each are rated at 2 tons each. Do you think 2 Powerwalls could handle a single 2 ton unit with the other phantom powers? My typical phantom power is around 300 watts and when I run my generator, that has a watt load meter on it, it reads right around 3000 watts, maybe a little more. If I kick on both AC units it reads a little over 5000watts load. Also, I set up the AC this way because all 'portable' generators are limited to 30amps due to their built in breakers and wire gauge. A 4 ton and higher unit uses more than 30amps so a full sized home generator, along with it's cost, would be needed. I got away with a 7kw Honda inverter generator I bought used for $1,500, converted it to propane and plumbed the house's 500 gallon propane tank to it's location.
BTW, I'm getting the 2 Tesla power walls via 'Grid Resiliency' program funded by the California PUC and based on Medical Base Line utility rate and located in an area where power shut offs due to high fire danger are common. Cost is $26,400 installed. I have to fund to get the install, but am rebated the full amount after permission to operate is granted by the utility company, usually about 3 months to obtain.

I think two Powerwall together can start up a 2-ton AC, although I suspect that Tesla will discourage you from doing this. The run time is another matter though. If you do not want a minisplit just for the bedroom, perhaps a window AC or a free-standing one can get you comfortable with a longer run time.

Please keep us posted on the installation. It's a heck of a deal to get two free Powerwalls.

 

[Offgrid Organic Farmer]

... The savings in off-peak electricity would also be very hard to justify.

I thought when they first announced the powerwall, the whole purpose was to charge them up using off-peak power and to use them during peak power.

How much difference is there between those two extremes?

 

[Koolau]

Every home in my township has at least one generator.

It is common to see two generators. One large unit and one small unit.

The small generators can power lighting and PCs. The small unit sips a gallon of fuel every 8 hours.

The big generators allow you to flush toilets, run laundry, and refrigerators & freezers, and to take showers. Those big units guzzle a gallon of fuel an hour.

Those homes run the big unit for one-hour each day, as they do laundry, take showers flush toilets, and bring the temps of freezers back down to appropriate temps.

In this manner, you consume the least amount of fuel. One hour each day running a big generator and 23 hours of running a small generator, means that you only consume 11 gallons each day tops. If you shut down the small one when you sleep, you can consume even less.

Nobody here has A/C, and most homes here burn firewood for heating.

One of our neighbors is a gunsmith. His insurance company insisted that he install a big generac to power his machine shop and security system. He regularly goes through $150 in fuel each month.

I have lived here for 15 years so far. During the past 15 years, our power company has never been capable of providing power for one-month continuously. Every month our power will go out at least once.

Just how it works here in rural areas of the East Coast.

Whoa! I thought we had it bad. Our outages are usually (fortunately) relatively brief. They range from a flicker - whereupon, we start resetting all the clocks to 2 or 3 minutes. SWAG is one power fail/month of the flicker variety. The 2 minute variety once or twice a year, but there is the occasionally 30 minute one. We did have the 18 hour one, but only once in 13 years.

Most power fails are due to wind. Just strong trades are enough to kill our power for a few minutes.

The good news is our condo has a large diesel generator that runs the elevators and walk-way lights as well as security cameras. Of course, we in our egg crate apartments are without power. I keep several battery powered lights around for the inevitable. Just don't think I could live where I had to depend (very often) on my own generator. Of course, YMMV.

 

[Offgrid Organic Farmer]

Whoa! I thought we had it bad. Our outages are usually (fortunately) relatively brief. They range from a flicker - whereupon, we start resetting all the clocks to 2 or 3 minutes. SWAG is one power fail/month of the flicker variety. The 2 minute variety once or twice a year, but there is the occasionally 30 minute one. We did have the 18 hour one, but only once in 13 years.

Most power fails are due to wind. Just strong trades are enough to kill our power for a few minutes.

The good news is our condo has a large diesel generator that runs the elevators and walk-way lights as well as security cameras. Of course, we in our egg crate apartments are without power. I keep several battery powered lights around for the inevitable. Just don't think I could live where I had to depend (very often) on my own generator. Of course, YMMV.

Maine is over 92% forest. Whenever there is a wind storm somewhere trees blow down. When trees blow down on power lines, from that spot going down line the next 20 townships will all lose power.

Maybe once a year our town loses power for a week.

Most power outages here are between 6 hours and 3 days.

 

[skipro33]

I think two Powerwall together can start up a 2-ton AC, although I suspect that Tesla will discourage you from doing this. The run time is another matter though. If you do not want a minisplit just for the bedroom, perhaps a window AC or a free-standing one can get you comfortable with a longer run time.

Please keep us posted on the installation. It's a heck of a deal to get two free Powerwalls.

I think with my solar still at work, charging the batteries with about 7kw of solar, I'd be good to go at least running the AC during peak solar generation.

The reason they are funding the batteries is because the CPUC is trying to eliminate peaking power generation as well as harden the grid. By focusing on micro generation, they figure they can draw down my batteries when I'm not expecting an outage for their own peaking needs. That's the deal; I have to agree on an equivalant draw down of 80% capacity 52 times a year or, once a week drain. The electric company uses this to keep from firing up peaking generators which are usually very environmentally unfriendly.

 

[NW-Bound]

I thought when they first announced the powerwall, the whole purpose was to charge them up using off-peak power and to use them during peak power.

How much difference is there between those two extremes?

As I mentioned in the earlier post at #19:

My Time-of-Day (TOD) rate in Phoenix: 24.09c/kWh during the peak summer hours of 2-8PM, and 7.3c/kWh outside that peak period.

Southern Cal Edison TOD rate: 43c/kWh for 4-9PM and 16c/kWh for off peak, for people with battery storage.

 

[NW-Bound]

I think with my solar still at work, charging the batteries with about 7kw of solar, I'd be good to go at least running the AC during peak solar generation.

The reason they are funding the batteries is because the CPUC is trying to eliminate peaking power generation as well as harden the grid. By focusing on micro generation, they figure they can draw down my batteries when I'm not expecting an outage for their own peaking needs. That's the deal; I have to agree on an equivalant draw down of 80% capacity 52 times a year or, once a week drain. The electric company uses this to keep from firing up peaking generators which are usually very environmentally unfriendly.

If you have 7 kW of solar, that's plenty good to run the 2-ton AC right there.

I did not know about the arrangement the utility has with you about tapping into your batteries. That's interesting. They have to work with Tesla in order to gain control of the Powerwalls in order to program the Powerwall operation. That's neat.

Of course when the grid goes down due to PSPS, you are disconnected from the grid because of the power cut-off, will be on your own and do not have to share the Powerwalls and your solar generation with anybody. It should work out great.

 

[Koolau]

As I mentioned in the earlier post at #19:

My Time-of-Day (TOD) rate in Phoenix: 24.09c/kWh during the peak summer hours of 2-8PM, and 7.3c/kWh outside that peak period.

Southern Cal Edison TOD rate: 43c/kWh for 4-9PM and 16c/kWh for off peak, for people with battery storage.

If your TOD system is more-or-less the way it's going to be, I'm wondering why someone hasn't come out with a cooling system that uses ice which is frozen when it's cheap and melted in a blower system when rates are high. Early car "air conditioning" used ice in the trunk with blowers to circulate air over the ice and into the cabin.

I'm not an engineer, but I think the only real trick would be sizing - but YMMV.

 

[MRG]

If your TOD system is more-or-less the way it's going to be, I'm wondering why someone hasn't come out with a cooling system that uses ice which is frozen when it's cheap and melted in a blower system when rates are high. Early car "air conditioning" used ice in the trunk with blowers to circulate air over the ice and into the cabin.

I'm not an engineer, but I think the only real trick would be sizing - but YMMV.

We have the opposite of what you describe. Off peak we heat bricks that are used for thermal energy on peak.

 

[NW-Bound]

If your TOD system is more-or-less the way it's going to be, I'm wondering why someone hasn't come out with a cooling system that uses ice which is frozen when it's cheap and melted in a blower system when rates are high. Early car "air conditioning" used ice in the trunk with blowers to circulate air over the ice and into the cabin.

I'm not an engineer, but I think the only real trick would be sizing - but YMMV.

I am sure people have been thinking about this for ages. The temptation comes from the fact that melting ice absorbs a huge amount of heat. The enthalpy of fusion of ice is 80 cal/g, which is 80% of the heat it takes to bring it from freezing to boiling.

The problem I think is in designing a vessel to contain that water volume as it turns into ice and expands. Having several hundred gallons of water leaking inside your home would cause a mess.

So, for now I just store excess solar energy gathered during the day into my lithium cell banks. In the middle of the summer, I usually have enough to run the ACs a bit past 8PM, when the electric rate drops from the on-peak rate to the off-peak rate.

Early and late in the summer, the ACs do not have to run as hard during the day, and I have more excess juice to store. The ACs can run until the early morning hours on solar energy, and sometimes even until sunrise the next day.

Right now, with the low at 65 and the high at 90, I have a surplus of solar power, even after running the pool pump and the water heater, plus the fridges and cooking. In the shoulder seasons, I often see the solar charge controllers go to sleep because the battery is full. With it being an off-grid system, I cannot export out to the grid, and the excess available energy is simply forfeited.

With an EV, I could charge it when I have some extra, but that will not be significant because most of the year I do not have any excess power anyway.

 

[Koolau]

I am sure people have been thinking about this for ages. The temptation comes from the fact that melting ice absorbs a huge amount of heat. The enthalpy of fusion of ice is 80 cal/g, which is 80% of the heat it takes to bring it from freezing to boiling.

The problem I think is in designing a vessel to contain that water volume as it turns into ice and expands. Having several hundred gallons of water leaking inside your home would cause a mess.

So, for now I just store excess solar energy gathered during the day into my lithium cell banks. In the middle of the summer, I usually have enough to run the ACs a bit past 8PM, when the electric rate drops from the on-peak rate to the off-peak rate.

Early and late in the summer, the ACs do not have to run as hard during the day, and I have more excess juice to store. The ACs can run until the early morning hours on solar energy, and sometimes even until sunrise the next day.

Right now, with the low at 65 and the high at 90, I have a surplus of solar power, even after running the pool pump and the water heater, plus the fridges and cooking. In the shoulder seasons, I often see the solar charge controllers go to sleep because the battery is full. With it being an off-grid system, I cannot export out to the grid, and the excess available energy is simply forfeited.

With an EV, I could charge it when I have some extra, but that will not be significant because most of the year I do not have any excess power anyway.

Again, since I'm not an engineer, I just sort of picture a couple of commercial ice makers sitting in your garage (so they don't heat up your interior as they make ice) making a few hundred pounds of ice when electricity is cheap. Before the rates change, you shut them down and shovel the ice into a plenum that feeds into your forced air system and recirculate your home's air over the ice. Hopefully, you have a drain in your garage (you DO have a drain in your garage, right?) The ice melt runs down the drain. Voilà. I'm guessing a couple of ice makers are cheaper than solar panels and a battery back up but I have NO experience in this realm. - IOW YMMV.

 

[braumeister]

When I was a kid, the local movie theater put up a big marquee sign that advertised "AIR CONDITIONING".

That was seriously novel at the time (1950s) because nobody had an air conditioner in their home.

What they actually did was put a bunch of big metal tubs at the back of the seating area, filled with blocks of ice. Then they had fans blowing air across the ice into the seating area.

It did actually cool the place down a little in the summer.

 

[Koolau]

When I was a kid, the local movie theater put up a big marquee sign that advertised "AIR CONDITIONING".

That was seriously novel at the time (1950s) because nobody had an air conditioner in their home.

What they actually did was put a bunch of big metal tubs at the back of the seating area, filled with blocks of ice. Then they had fans blowing air across the ice into the seating area.

It did actually cool the place down a little in the summer.

As a kid, I knew a guy who had a "refrigerated" truck. It was simply a box truck with cork covered with plywood. The cooling system? Blocks of ice in a horse trough near the cab. It was quite effective. I really enjoyed climbing inside when it was hot outside.

 

[NW-Bound]

Again, since I'm not an engineer, I just sort of picture a couple of commercial ice makers sitting in your garage (so they don't heat up your interior as they make ice) making a few hundred pounds of ice when electricity is cheap. Before the rates change, you shut them down and shovel the ice into a plenum that feeds into your forced air system and recirculate your home's air over the ice. Hopefully, you have a drain in your garage (you DO have a drain in your garage, right?) The ice melt runs down the drain. Voilà. I'm guessing a couple of ice makers are cheaper than solar panels and a battery back up but I have NO experience in this realm. - IOW YMMV.

Ah, I did not know you were thinking of a "lo-tech" solution, which is easier to implement. Cool!

Now, I have to do some rough calculations to "size up" the requirement.

A 100-lb block of ice when melting absorbs 3,630,000 calories or 14,400 BTU.

This summer, I did not turn on the central 5-ton AC, and abandoned the upstairs to the heat, and cooled only the downstairs with the 2 new minisplits. One is a 3/4 ton, and the other a 1-1/2 ton. Their combined cooling power is then 9000+18000 = 27,000 BTU/hr.

Uh Oh! That's roughly 200 lbs of ice per hour. And for the 6 hours of peak TOD rate charges, I would need 1,200 lbs of ice. Yikes!

I don't know how large a commercial ice maker I would need, but it looks like that's a lot of water that I would not want to go down the drain each day, and would have to recycle.

And how much energy it takes to make that ice? The Web site energy.gov says it's about 1.1 kWh per 100 lbs of ice, for a typical ice maker. As I would use 200 lbs/hr, that 2.2 kWh/hr turns out to be in the same ball park as what my 2 minisplits draw, when they are running at top speed.

So, energy wise, it's about the same, and using ice would work to time-shift the energy draw for ice making to off-peak period.

But, but, but shoveling 1,200 lbs of ice per day? And taking the melted water back out to the garage by the 5-gal pail? It's about 30 pails.


PS. I will soon have a total storage of 34 kWh in my 2 lithium banks. That's equivalent to 3100 lbs of ice, for cooling purposes. The batteries weigh about 800 lbs, and take only a few cubic feet. They are a lot more expensive than water, that's for sure.


PPS. CORRECTION NEEDED!

I misread the info on energy.gov regarding power consumption of the typical ice maker. It says 5.5 kWh for 100 lbs of ice, not 500 lbs. Yikes! This means the typical icemaker cannot replace an AC.

 

[Offgrid Organic Farmer]

A powerwall as a part of a solar power system would depreciate at the same rate as the entire solar system depreciates [1/7th per year]. But if you do not have a solar power system, then I am not sure if you can depreciate a powerwall.

It often requires a very sharp pencil to make the math work for solar power, but the depreciation angle is HUGE since the total expense must be depreciated over a 7-year span. It is easy to figure 1/7th per year for 7 years.

With depreciation, the 'pay-back' should always happen in less than 7 years.

 

[bjorn2bwild]

Again, since I'm not an engineer, I just sort of picture a couple of commercial ice makers sitting in your garage (so they don't heat up your interior as they make ice) making a few hundred pounds of ice when electricity is cheap. Before the rates change, you shut them down and shovel the ice into a plenum that feeds into your forced air system and recirculate your home's air over the ice. Hopefully, you have a drain in your garage (you DO have a drain in your garage, right?) The ice melt runs down the drain. Voilà. I'm guessing a couple of ice makers are cheaper than solar panels and a battery back up but I have NO experience in this realm. - IOW YMMV.

Ah, I did not know you were thinking of a "lo-tech" solution, which is easier to implement........


I don't know how large a commercial ice maker I would need, but it looks like that's a lot of water that I would not want to go down the drain each day, and would have to recycle...........
But, but, but shoveling 1,200 lbs of ice per day? And taking the melted water back out to the garage by the 5-gal pail? It's about 30 pails.

A simple low tech system already exists - the humble evaporative cooler. In a low humidity environment, they work quite well, just add ice to the water. I do this on a small scale during the PSPS outages here in California.
In higher humidity settings, the most efficient model would work like a conventional AC system. Replace the compressor/condenser unit with an ice bath and recirculating pump. The cold water would be distributed to a radiator/fan/duct network. The bath would be recycled - bleed water out to be refrozen and replaced. No waste, and most likely impractical but conceptually interesting.

 

[NW-Bound]

A simple low tech system already exists - the humble evaporative cooler. In a low humidity environment, they work quite well, just add ice to the water. I do this on a small scale during the PSPS outages here in California.
In higher humidity settings, the most efficient model would work like a conventional AC system. Replace the compressor/condenser unit with an ice bath and recirculating pump. The cold water would be distributed to a radiator/fan/duct network. The bath would be recycled - bleed water out to be refrozen and replaced. No waste, and most likely impractical but conceptually interesting.

We are getting adrift away from battery storage, but on the subject of AC and cooling, I've got to add something more.

Yes, the evaporative cooler or "swamp cooler" as it is affectionately called used to be quite popular in the southwest. In fact, prior to the 1980s, most homes only had the swamp cooler and the ACs were not widespread because of the cost.

It works well here because of the low humidity in the SW, and can provide indoor temperature in the 70s when the dew point is 50F or less. Because the swamp cooler adds humidity, its discharge temperature has to be in the low 70s to provide comfort. In contrast, dry air put out by an AC can feel very comfortable at 80F.

But when the monsoon season comes in August and brings moisture to boost the dew point up, the temperature that the swamp cooler blows out can be greater than 85F with humidity, and it no longer feels that good. Of course 85F with humid air is still better than having no cooling at all and suffering 115-120F temperature, but people now long for an AC.

The swamp cooler has lost its popularity in the recent years. It used to be that early in the summer when home owners started to prep up to combat the heat, Home Depot and Lowes would carry cooler accessories and replacement parts such as cooler aspen pads and recirculation pumps. Now, they still carry these, but not at the same magnitude.

Having lived here for more than 4 decades, I have had plenty of experience with swamp coolers. Now, in order to cool the air further without adding even more humidity to the air, there's a thing called a 2-stage cooler. The first stage is another swamp cooler stage that precools the air that then enters the conventional stage. It is supposed to cool the air by another 5F or so, and that can help. I once thought about getting that, but never did. I don't know if they still make that.

Now, another reason the swamp cooler has lost its popularity is that new homes tend to be of the 2-story construction, instead of the one-level ranch home. People are afraid to go up that high to do the required annual maintenance of the cooler.

Additionally, new subdivisions do not want the ungainly look of the swamp cooler, or even a rooftop AC, on the tile roof. So, there are no new homes with a swamp cooler, and in fact it is not even possible to retrofit one onto a new home even if the HOA does not ban it.

But, but, but, can a swamp cooler provide pre-cooling to an AC to help its efficiency? You betcha. I had a pre-cooler for my AC once. It is not much more than wetted pads mounted on the AC to cool the exterior air before it is drawn past the condenser coil. The water flow to wet the pad is controlled by a solenoid which is wired onto the AC to turn on along with it.

The AC precooler works well, but even a simple thing like that takes some maintenance (nozzles getting clogged, water overspraying and causing corrosion, solenoid getting stuck, etc...). I remember messing with it all the time. And that's why you don't see AC pre-coolers being sold anymore.

 

[Koolau]

A simple low tech system already exists - the humble evaporative cooler. In a low humidity environment, they work quite well, just add ice to the water. I do this on a small scale during the PSPS outages here in California.
In higher humidity settings, the most efficient model would work like a conventional AC system. Replace the compressor/condenser unit with an ice bath and recirculating pump. The cold water would be distributed to a radiator/fan/duct network. The bath would be recycled - bleed water out to be refrozen and replaced. No waste, and most likely impractical but conceptually interesting.

Yes, this was sort of my idea. Freeze water when electricity is cheap and circulate air over the ice (or circulate the chilled water) and collect the water for refreezing. According to NW Bound, this would be at best a wash from an energy standpoint. I have no ability to check the calculations but I'm guessing they are substantially correct.

Electricity in Paradise is the most expensive in the USA. Folks who must use AC to "survive" have electric bills in the multi hundreds of dollars per month. We chose both our locations to allow the trades to blow through. No AC is required though there are occasions it would be nice. Electric bills are $80. YMMV