All electricity equal or not?

ajdelange

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I hope the point that solar is pretty bad as a backup source unless you have a lot of battery wasn't missed.
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drscot

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Solar is very low maintenance for decades. Compared to a generator which requires more periodic maintenance and can break down. Also the energy supply is free (light) for solar, as opposed to natural gas which is not free.

You just have a higher upfront cost with solar, but this is getting cheaper by the day.
That is true, except for the fact that even figuring the cost of natural gas and maintenance, the benefits outweigh the disadvantages under some circumstances. Yes, solar has advantages but disadvantages as well. My generator requires only annual maintenance. Oil change and plug change, and check up. It automatically does a weekly checkup. My solar isn't free either. I'm paying for my system for 12 years,, but I wrote a check for my generator system installed, and like a generator, solar is also manmade and can malfunction. If not, there would be no need for warranty coverage. When the grid goes down here for lengthy periods as does happen, solar is of little use. If it goes down at night, it produces zero. If I have an expensive battery backup (and it is expensive), it won't run my entire household (all electric) for as long as I need it to. If it is during the winter with low southern sun, cloud cover and maybe snow, the production from the solar panels will not be sufficient to power my household. If battery backup can't be completely recharged during cold weather and suboptimal conditions and prolonged outages, somebody is going to be cold in their house and it won't be me. I'm all for solar. That's why I inked the deal, but it isn't a panacea. It has limitations just like solar does. How many solar jets do you see traversing the sky? Have you ever boarded one? You may not for your entire life. How many solar generators did they ship into Texas to save people from freezing to death when the grid failed? You are correct in the microcosm, but you are missing the macrocosm. Each fits together like pieces of a jigsaw puzzle. My home may be one of the most energy integrated homes in my state. It is a geothermal home with the most up to date (at the time of construction) energy efficient innovations available. The 20 Kv natural gas standby generator is state of the art and I guarantee you there isn't a solar unit that can keep up with it under high load and poor solar conditions anywhere, yet I have contracted to put in a solar system that is guaranteed to produce 98% of my electrical needs on an annual basis. The solar is not designed to produce emergency (grid down) power. It is designed to produce daily power and bank extra production in the grid, which of course if the grid is down, it is not accessible. The generator is not designed to produce day in and day out power, but emergency (grid out) power. It shines at that and solar falls short. Day in and day out, the generator will handle, but not nearly as economically as solar. When Hurricane Sandy hit New York and New Jersey, how much solar energy was being generated reliably? Do you know? Look it up. What happened with generators exactly like mine? As long as they had gas supply and were not submerged in water, they ran without a hiccup for over 3 weeks straight, providing uninterrupted power to their families. Solar? No way, but solar wasn't designed for that. Solar does its job beautifully, as do quality generators. You are confusing the job requirements. Both are excellent, and both have different jobs. Once my solar is installed, I'll have both, and I am not pooh poohing either one.
 
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drscot

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I hope the point that solar is pretty bad as a backup source unless you have a lot of battery wasn't missed.
Read my response.
 

happy intruder

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You definitely have a point there. I am adding a solar array to my home now that is caculated to generate 98% of my needs with the new configuration, so I will likely charge mine during the day. I'm retired, so I can do that (eat your hearts our!) LOL! Mine runs on natural gas rather than propane so it is cheaper, but it is more than the 10 cents per KwH that I pay the grid. I paid the sales tax and increased property value property taxes on my Generac so Big Brother still has his finger in the pie, as well as poking me in the eye too. The gist of what I was saying was if I was charging at night and a power outage switched over to generator unawares to me if there would be an issue with the Tesla, but if I am successful charging from my solar array, it won't be an issue. Thank you for your input.
I have been looking at Generac for about 2 months now....they discontinued the 20kW so I only have access to 22kW, 24kW or 18kW.....they had a "authorized dealer" call me and make appointment to come over........I live in Irvine and have a 99% sun on the roof....when he got here, I showed where I wanted it ti go.....first thing he said after introductions was, you need a 24kW unit....well my house is s story and 2450 sqft.....The average temp is 75 and our neighborhood grid goes out 3 to 4 times durning the summer because it was built incorrectly......our cut-de-sac is the only only that has no power.....they know the problem, but it would cost about 2.5 million to fix, so they dont so it....

so the installer, looked around and I have a gas run of about 8 feet and the electrical is about 30ft going up thru the garage and exiting on the side of the house and across roof line and down to Generac.....after he looked around and I said I wanted the automatic transfer switch located next to the panel where the line went into the garage.....no issue.....I asked him to quote me for all three generations and include a line item for electrical and gas plumbing.....I know the generators range from $4895 to $5300......

two days later, I get a quote for $19875, 21,000 and 22500.....he did not itemize like I asked and gave me only 10 days to respond.....I asked him what the install costs are and have never heard from him after several emails and calls.....I almost wet my pants laughing.....

needless to say I called Generac and explained this....the I got a survey....I filled out the survey and got a call last week from their customer service department....I told them the story again and was told they would get me another contractor to call me.....have heard nothing.....

I can get the 22kW from Lowes for $4875 - 10% for special buy, then get 10% veteran discount.....pick up at store or have delivered.....

I really like the Generac product and they will give me 7yr warranty.....but I do not recommend their contractors....both time I spoke with them, they were in utter disbelief that there contractors were raping the customer.....

so, I will just wait and see what happens
 

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two days later, I get a quote for $19875, 21,000 and 22500.....he did not itemize like I asked and gave me only 10 days to respond.....I asked him what the install costs are and have never heard from him after several emails and calls.....I almost wet my pants laughing.....
For that much, you'd probably be better off going solar with battery backup. In fact that might be the better option regardless. Where you live, when the power is least reliable, solar is delivering in spades.

It would probably be twice that cost, but would permanently reduce your power bill too.

Edit: Also, I suspect you are underestimating the costs involved in installation. There is a lot of money in those switching systems, a lot of trenching, permitting, plus a lot of expensive cabling and other parts. The generator itself is just the tip of the iceberg.
 
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happy intruder

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For that much, you'd probably be better off going solar with battery backup. In fact that might be the better option regardless. Where you live, when the power is least reliable, solar is delivering in spades.

It would probably be twice that cost, but would permanently reduce your power bill too.

Edit: Also, I suspect you are underestimating the costs involved in installation. There is a lot of money in those switching systems, a lot of trenching, permitting, plus a lot of expensive cabling and other parts. The generator itself is just the tip of the iceberg.
there is no trenching at all.....gas line is right next to where I will install and no trenching for electrics.....ATS is going in right next to panel.....some people have had systems installed for $8500......there is no under estimating.
 

jhogan2424

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there is no trenching at all.....gas line is right next to where I will install and no trenching for electrics.....ATS is going in right next to panel.....some people have had systems installed for $8500......there is no under estimating.
My Generac is installed just across from the meter and panel at my place in the hills. The auto transfer switch, mess of conduit, and labor for that wiring was about half of my entire cost. That has been several years though and I’m sure installers vary. I have pretty much the same setup at both my home and getaway house, one on natural gas and the other on propane and they both work flawlessly. It keeps my internet and security cams running with frequent outages in the sticks and gives me peace of mind that I can look in at my place anytime from anywhere. The Generac should serve you well.

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happy intruder

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My Generac is installed just across from the meter and panel at my place in the hills. The auto transfer switch, mess of conduit, and labor for that wiring was about half of my entire cost. That has been several years though and I’m sure installers vary. I have pretty much the same setup at both my home and getaway house, one on natural gas and the other on propane and they both work flawlessly. It keeps my internet and security cams running with frequent outages in the sticks and gives me peace of mind that I can look in at my place anytime from anywhere. The Generac should serve you well.

FF438649-BBB2-4C1D-87BD-89F080B1E417.jpeg
what did your Generac cost and what was install cost?
 

jhogan2424

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what did your Generac cost and what was install cost?
The 20kw was about 6k and with the transfer switch and installation right around 9k total. The 16kw I have at the other location was slightly less. I just looked at the Owner’s manual and that was what I had scribbled inside next to the installer’s phone number.
 

happy intruder

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The 20kw was about 6k and with the transfer switch and installation right around 9k total. The 16kw I have at the other location was slightly less. I just looked at the Owner’s manual and that was what I had scribbled inside next to the installer’s phone number.
thanks....the 22kW I am getting includes ATS for about 5300......plus Lowes has a special 10% OFF and then a vet discount of 10%....so it is really a good deal....the installers around here are greedy jerks.....generac told me I can use any certified electrician and still get warranty.....they also have a deal now that includes a 7yr warranty.....so I will be looking at my installer.....
 


jhogan2424

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No problem. Sounds like a good deal to me. I didn’t have a lot of options on where to purchase mine at the time. Note the 16kw Generac is only set up to power one of the two central air conditioners along with the rest of the house. I didn’t see the need to go bigger with the generator just to be able to add the other A/C since I only occupy that house about one weekend a month. The generators work great and exercise themselves about 20 minutes every Saturday at noon so not much maintenance. I’m sure you will be pleased.
 

happy intruder

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No problem. Sounds like a good deal to me. I didn’t have a lot of options on where to purchase mine at the time. Note the 16kw Generac is only set up to power one of the two central air conditioners along with the rest of the house. I didn’t see the need to go bigger with the generator just to be able to add the other A/C since I only occupy that house about one weekend a month. The generators work great and exercise themselves about 20 minutes every Saturday at noon so not much maintenance. I’m sure you will be pleased.
thanks.....my house is a 2-story, 2450sqft and I have one 4-ton carrier a/c.unit...it is 2yrs old and work very well....we have 2 refrigerators, two cars that require plug in....so when we lose power my wife freaks out.....I am still looking at an 18kW because the 20kW is no longer manufactured......dont want over kill, but not that much difference on price
 

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thanks.....my house is a 2-story, 2450sqft and I have one 4-ton carrier a/c.unit...it is 2yrs old and work very well....we have 2 refrigerators, two cars that require plug in....so when we lose power my wife freaks out.....I am still looking at an 18kW because the 20kW is no longer manufactured......dont want over kill, but not that much difference on price
I would go with the 20kw then since you could potentially be charging both cars and running A/C. Not sure if you have any other 240 appliances but I would still go with the 20kw since not much price difference. Another reason I went with the 16kw in the one application was because it is on propane and I was thinking of fuel consumption. I do have a 1,000 gallon propane tank but that is still finite. Since you are on NG and no worries of running out I would pay slightly more and get the 20kw.
 

ajdelange

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A little arithmetic: A 4 ton A/C is going to pull about 4 kW. Each fully charging BEV is going to pull 11.5kW. Thus a 20 kW generator is not capable of running the A/C and charging to BEV simultaneously but it is capable of supporting all three of those if you manage the loading on it. I've said earier in this thread that you don't want to charge BEV on a generator unless it's absolutely necessary because the cost of a generated kWh is usually several times the cost of one bought from the utility. The same goes for other large loads such as clothes dryers and electric ovens. Avoid using them when the power is out if you possibly can. This is especially important if you are on propane as the events that cause prolonged power outages may prevent the propane truck from getting out to you to refill your tank.

I thought I'd gotten into load management in this thread but it must have been somewhere else. Deferring laundry, using the barbecue instead of the oven, charging one BEV at at time are all examples of load management. You can even handle more than one air conditioner if you have a proper load management system in place. This is a system that is usually a part of the transfer switch that measures the generator output and, when it gets high, starts to turn off loads in order to keep the generator load at about 80% of capacity. For example, if you have two A/C connected and they both come on the load management system senses the current rise and shuts off, say, the clothes dryer. If the clothes dryer was running and that reduces the load enough then both A/C continue to run. If the clothes dryer was not running then disconnecting it obviously doesn't help and the system shuts off another load - perhaps one of the A/C. When the remaining A/C has satisfied it thermostat it shuts down and the system senses reduced load and puts the second one back on. The order in which loads are shed is set into the system so that, for example, the main house A/C takes precedence over the one that serves the mother-in-law suite.
Fairly recent changes in the NEC WRT generators have made automatic load shedding systems common. A generator must be capable of serving all the loads connected to it. The goal of shedding equipment is automatically insure this.

The obvious question is "how big a generator should I have". It should be obvious that this depends on how you use electricity. To determine that you need to monitor your usage for an extended period, create a histogram from the logs and from that prepare the complementary cumulative distribution function. Now I don't expect that anyone will be able, prepared or inclined to do this but bear with me for a moment. The graph below shows such a histogram going back to March 3 of this year. Mean consumption was 3.62 kW and this implies an average demand of 86.8 kWh per day which, while it isn't Al Gore, is about triple the average American household's use. The house has 400 A (96 kW) service and based on this I bought a 48 kW generator (200A). Was that smart? No, it wasn't, because the cumulative frequency curve shows that I never used more than 27 kW and used more than 25 kW less that 0.00001 of the time which is 5 minutes per year.
Tesla Cybertruck All electricity equal or not? Loaddist


Suppose that instead of a 48 kW generator I had chosen a 20 kW unit. My usage history shows that I use more than 80% of that (16 kW) 0.002 of the time so that during a 2 week outage I would have to shed something for a total of 14*24*60*.002 = 40.32 minutes or 24*60*.002 = 2.88 minutes per day. I don't think having some load or other shed for 3 minutes each day is so burdensome and so think that in fact a generator capable of 16 kW at 80% load (20 kW machine) would have, based on this chart been fine for me.

All that's dandy but if you don't have the historical data, how do you pick a generator size? You do, in fact, have some historical data and that is to be found on your electrical bill. As the picture above shows a demand pattern depends on three variables: a baseline load which is present 99.9% of the time on top of which there is a varying load which follows a Weibull distribution quite closely. The history shown by the heavy line is approximated well by a flat line up to 0.85 kW (the baseline load) and, above that, by the thinner blue line described by exp( -((kW - base)/sigma)^gamma) in which base = 0.85 kW, sigma = 3.2089 and gamma = 1.2094. Note that if gamma = 1, and the actual value is close, the distribution is a simple exponential with scale parameter sigma = (average - base) and
exp(- (kW - base)/(average - base)) then gives the dashed curve shown on the plot. This can be solved for the load for a particular desired fraction as

kW = (average - base)*(-2.303*log(f)) + base

With the observed average of 3.62 kW and a baseline of 0.85 kW for the same 0.002 fraction we'd have (3.62 - 0.85)*(-2.303*log(.002)) + 0.85 = 18.0676 kW as 80% of the generator capacity requiring a 22.4 kW machine.

To estimate the size of the generator you need go to your electric bill and find your total consumption for a year (kWh). Divide this by (365*24) to get the average kW/day, Now look to see if there is seasonal variation. If there is find the part of the year with the biggest demand and calculate the daily average for that period. While my last 143 days have averaged 3.62 kWh/da in the winter the average goes up to 4.91 kWh/day Putting that into the sizing formula we get 1.25*(4.98 - 0.85)*(-2.303*log(.002)) + 0.85 = 32.9387. Of the B&S Fortress generators I was looking at (1800 rpm = quiet) I chose the 48 kW model when it appears the 35 kW model would have been fine. I have never had a shedding incident and never observed generator load greater than 16.5 kW (47% of a 35 kW generator). Not surprising as loads that big occur anout 0.2% of the time and the odds of that being during a power outage are small.
 

happy intruder

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A little arithmetic: A 4 ton A/C is going to pull about 4 kW. Each fully charging BEV is going to pull 11.5kW. Thus a 20 kW generator is not capable of running the A/C and charging to BEV simultaneously but it is capable of supporting all three of those if you manage the loading on it. I've said earier in this thread that you don't want to charge BEV on a generator unless it's absolutely necessary because the cost of a generated kWh is usually several times the cost of one bought from the utility. The same goes for other large loads such as clothes dryers and electric ovens. Avoid using them when the power is out if you possibly can. This is especially important if you are on propane as the events that cause prolonged power outages may prevent the propane truck from getting out to you to refill your tank.

I thought I'd gotten into load management in this thread but it must have been somewhere else. Deferring laundry, using the barbecue instead of the oven, charging one BEV at at time are all examples of load management. You can even handle more than one air conditioner if you have a proper load management system in place. This is a system that is usually a part of the transfer switch that measures the generator output and, when it gets high, starts to turn off loads in order to keep the generator load at about 80% of capacity. For example, if you have two A/C connected and they both come on the load management system senses the current rise and shuts off, say, the clothes dryer. If the clothes dryer was running and that reduces the load enough then both A/C continue to run. If the clothes dryer was not running then disconnecting it obviously doesn't help and the system shuts off another load - perhaps one of the A/C. When the remaining A/C has satisfied it thermostat it shuts down and the system senses reduced load and puts the second one back on. The order in which loads are shed is set into the system so that, for example, the main house A/C takes precedence over the one that serves the mother-in-law suite.
Fairly recent changes in the NEC WRT generators have made automatic load shedding systems common. A generator must be capable of serving all the loads connected to it. The goal of shedding equipment is automatically insure this.

The obvious question is "how big a generator should I have". It should be obvious that this depends on how you use electricity. To determine that you need to monitor your usage for an extended period, create a histogram from the logs and from that prepare the complementary cumulative distribution function. Now I don't expect that anyone will be able, prepared or inclined to do this but bear with me for a moment. The graph below shows such a histogram going back to March 3 of this year. Mean consumption was 3.62 kW and this implies an average demand of 86.8 kWh per day which, while it isn't Al Gore, is about triple the average American household's use. The house has 400 A (96 kW) service and based on this I bought a 48 kW generator (200A). Was that smart? No, it wasn't, because the cumulative frequency curve shows that I never used more than 27 kW and used more than 25 kW less that 0.00001 of the time which is 5 minutes per year.
Loaddist.jpg


Suppose that instead of a 48 kW generator I had chosen a 20 kW unit. My usage history shows that I use more than 80% of that (16 kW) 0.002 of the time so that during a 2 week outage I would have to shed something for a total of 14*24*60*.002 = 40.32 minutes or 24*60*.002 = 2.88 minutes per day. I don't think having some load or other shed for 3 minutes each day is so burdensome and so think that in fact a generator capable of 16 kW at 80% load (20 kW machine) would have, based on this chart been fine for me.

All that's dandy but if you don't have the historical data, how do you pick a generator size? You do, in fact, have some historical data and that is to be found on your electrical bill. As the picture above shows a demand pattern depends on three variables: a baseline load which is present 99.9% of the time on top of which there is a varying load which follows a Weibull distribution quite closely. The history shown by the heavy line is approximated well by a flat line up to 0.85 kW (the baseline load) and, above that, by the thinner blue line described by exp( -((kW - base)/sigma)^gamma) in which base = 0.85 kW, sigma = 3.2089 and gamma = 1.2094. Note that if gamma = 1, and the actual value is close, the distribution is a simple exponential with scale parameter sigma = (average - base) and
exp(- (kW - base)/(average - base)) then gives the dashed curve shown on the plot. This can be solved for the load for a particular desired fraction as

kW = (average - base)*(-2.303*log(f)) + base

With the observed average of 3.62 kW and a baseline of 0.85 kW for the same 0.002 fraction we'd have (3.62 - 0.85)*(-2.303*log(.002)) + 0.85 = 18.0676 kW as 80% of the generator capacity requiring a 22.4 kW machine.

To estimate the size of the generator you need go to your electric bill and find your total consumption for a year (kWh). Divide this by (365*24) to get the average kW/day, Now look to see if there is seasonal variation. If there is find the part of the year with the biggest demand and calculate the daily average for that period. While my last 143 days have averaged 3.62 kWh/da in the winter the average goes up to 4.91 kWh/day Putting that into the sizing formula we get 1.25*(4.98 - 0.85)*(-2.303*log(.002)) + 0.85 = 32.9387. Of the B&S Fortress generators I was looking at (1800 rpm = quiet) I chose the 48 kW model when it appears the 35 kW model would have been fine. I have never had a shedding incident and never observed generator load greater than 16.5 kW (47% of a 35 kW generator). Not surprising as loads that big occur anout 0.2% of the time and the odds of that being during a power outage are small.
I have looked at the last 18 months of my usage.....I average 1.24kW per day....I do not plan on running the a/c and charging both cars at the same time. A/C will probably run from 1300 to 1700 unless temps are over 95.....we have an average temp in jun-oct of about 81F.....we run air when we have company and keep thermostat set to 76F......we have gas applicants and charcoal and LP and natural gas grills....we have 2 refrigerators computers and tvs and internet....

I think we could easily get by with a 16, 18 or 20kW generator...but Generac discontinued the 20kW....it is clean electricity.......we will use natural gas to run it....there is just not a big price difference in the three so I will go fo the bigger one.....

the reason for our wanting to get a generator is my wife is terrified of a grid attack.....she is also terrified of earthquakes.....she has 10 gal of fresh water in her car and changes in every 2 months....waters the plants, hahahaha.....in addition to all that, her car is a rolling Nordstrom....keeps enough clothes and shoes for 60 days it seems like.....so, she just wants to be prepared.....

I know an earthquake could take out all of SoCal and gas line will be shut down or destroyed......if that happens we will be worrying more about living than whether we have lights....plenty of water though with a 32,000 gal pool....so I guess she is set...hahahah
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