All electricity equal or not?

[drscot]

Yes, you absolutely can charge your Tesla from your Generac but only if it is owned by the government. I say this because the Tesla manual says you should not charge from a privately owned generator. I'm not kidding about what the manual says but I am certainly being tongue in cheek about not being able to do it. There are some members here who have some interesting ideas about what can and cannot charge a Tesla and as to what's in or not in a generator. Don't know if they will emerge again this time round but there is only one reason you shouldn't charge from a generator and that's the cost. Given what you pay for propane and the efficiency of small machines a kwh from your generator is quite a bit more expensive than one bought from the utility. Most outages are a few hours so wait to dry clothes, turn off e-heat, don't run your kilns, don't use your electric ovens and don't charge during a power outage unless you have to. Less propane used means less $ AND that your tank will last longer in a prolonged outage too. But if you have to, you have to (hasn't happened to me - yet).

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.

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[ajdelange]

In a typical installation your house will be connected, via a transfer switch to either the utility or the generator - never both. The solar system's inverter(s) will be connected to the utility side. When the utility goes down the generator starts and the transfer switch throws. Your house is disconnected from the utility and the solar system. If this happens in the middle of the night while your truck is charging the charge will be interrupted when the power goes down. The generator will wait about 30 sec before starting and after a couple more seconds, when the generator is up to speed the transfer switch will throw, the truck will sense normal voltage and the charge will resume. The THD from your generator is good enough to run the appliances in your house and good enough to charge your truck (I don't think your truck even cares).

When the utility is up it doesn't matter when you charge. If the solar system is producing then energy from the array will go to the truck to the extent that the array output can meet the charging load and any short fall will come from the utility. Assuming you have 1 for 1 net metering and flat rates (a kWh is x ¢ any time of day and you get a credit of x ¢ for each kWh you send the utility) it doesn't matter when you charge. If the rates are time adjusted then it gets more complicated but it's probably not worth long nights with the Excel Solver trying to figure out the optimum strategy. If you drive the typical 10,000 miles a year that means about 5000 kWh electricity used which, at 10¢/kWh is $500.

Now if you want to be able to boast "My truck runs on fusion." or "My fuel cost for the truck is nothing per mile" then you want to see to it that your truck charges exclusively from the sun. To do that obviously you have to charge when the PV array is producing and you have to set the truck's charge rate to less than the array is producing. It looks like this.

Charging started at a little after noon at the maximu 11.5 kW. As the solar system was producing over 20 kW for most of that time and the total load, including the car was always less than that all the energy going to the car has to have come from the PV array. Exception was the brief interval at about 12:30 when a cloud went over and production dropped to 8 kW. In that interval some of the energy going to the car came from the utility.

 

[drscot]

US mains power is transmitted as a 60 Hz near sine wave of amplitude 339.4 V. I say "near" because the waveform has some energy in it at frequencies other than 60 Hz i.e. at harmonics of 120 Hz, 180 Hz, 240 Hz etc, These distort the sin wave making it less smooth. The quality of power is often expressed in terms of Total Harmonic Distortion which is the ratio of the power at 120, 180, 240... Hz divided by the power in the fundamental (60 Hz). Utility power is quite clean - harmonic distortion of a percent or 2. Power from a good generator is perhaps a little higher (up to 3%) and power from cheapie generators can be higher than that. Harmonics can be a problem in machines that use steel such as a transformer or motor. The higher frequencies get converted to heat rather than work and gear gets hot. But your Tesla doesn't have any of this exposed to the line. The first thing it does is rectify the incoming waveform and it can do that to a square wave as well as a sine wave. Some people here think it can't and some people here think cheap generators have modified sine inverters in them. Neither true. If you want to be nervous about this get a THD meter (built into a clamp on Ammeter) and measure your generator's THD. I really don't know what to expect from Generac but Kohler and B&S ar in the couple percent department. Solar inverters are as good as the utility.

Thank you for that detailed explanation. I guess the term "cheap" is relative when it comes to generators, but Generac is an industry leader and the standby I bought at the top of their lineup, so I am pretty sure it is a quality unit. I paid $8500 installed for mine 5 years ago. With hurricane Sandy, Generacs were reported to run for 3 plus weeks without a hiccup provided they had natural gas and didn't get submerged. Mine just runs and runs and runs with power outages. Out here where the grid is less than premium it runs plenty, and nothing in my home over a 5 year period appears to have suffered from the power it generates, so I guess I'm safe. Of course, like I said (or intended to imply), I would only charge with the generator unintentionally during outages while asleep with automatic generator startup. Daytime solar panel "free" charging of course would be preferable. Nothing of course is "free", not even solar.

 

[drscot]

In a typical installation your house will be connected, via a transfer switch to either the utility or the generator - never both. The solar system's inverter(s) will be connected to the utility side. When the utility goes down the generator starts and the transfer switch throws. Your house is disconnected from the utility and the solar system. If this happens in the middle of the night while your truck is charging the charge will be interrupted when the power goes down. The generator will wait about 30 sec before starting and after a couple more seconds, when the generator is up to speed the transfer switch will throw, the truck will sense normal voltage and the charge will resume. The THD from your generator is good enough to run the appliances in your house and good enough to charge your truck (I don't think your truck even cares).

When the utility is up it doesn't matter when you charge. If the solar system is producing then energy from the array will go to the truck to the extent that the array output can meet the charging load and any short fall will come from the utility. Assuming you have 1 for 1 net metering and flat rates (a kWh is x ¢ any time of day and you get a credit of x ¢ for each kWh you send the utility) it doesn't matter when you charge. If the rates are time adjusted then it gets more complicated but it's probably not worth long nights with the Excel Solver trying to figure out the optimum strategy. If you drive the typical 10,000 miles a year that means about 5000 kWh electricity used which, at 10¢/kWh is $500.

Now if you want to be able to boast "My truck runs on fusion." or "My fuel cost for the truck is nothing per mile" then you want to see to it that your truck charges exclusively from the sun. To do that obviously you have to charge when the PV array is producing and you have to set the truck's charge rate to less than the array is producing. It looks like this.

Charging started at a little after noon at the maximu 11.5 kW. As the solar system was producing over 20 kW for most of that time and the total load, including the car was always less than that all the energy going to the car has to have come from the PV array. Exception was the brief interval at about 12:30 when a cloud went over and production dropped to 8 kW. In that interval some of the energy going to the car came from the utility.

Fantastic! Thank you so much! You hit the nail on the head! I'm going to print that out and send it to my solar guy. Yes, our standard rates are 10 cents/KwH. Sometimes only 5 cents. June through Sept it goes to a demand rate for 5 hours per day only. I don't remember what the production is on my yet to be installed system, but they guarantee it in writing within 5% or they cut a check annually. I told him I'd just throw tarps over the panels until the system was paid off! LOL! I'll have to put a pencil to that one! We could be in a nuclear winter and they would cut the check every year.
Thanks again for taking the time to give such a detailed explanation.

 

[jhogan2424]

No problems with my Generac standby. It always starts up on its’ own and runs the whole house just like it’s supposed to. It ran my house for several days when ice took down trees and lines a few years ago. I change the oil every couple years if I happen to think about it and I replaced the starting battery once.

 

[drscot]

Today at 1:02 PM

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ajdelange said:
In a typical installation your house will be connected, via a transfer switch to either the utility or the generator - never both. The solar system's inverter(s) will be connected to the utility side. When the utility goes down the generator starts and the transfer switch throws. Your house is disconnected from the utility and the solar system. If this happens in the middle of the night while your truck is charging the charge will be interrupted when the power goes down. The generator will wait about 30 sec before starting and after a couple more seconds, when the generator is up to speed the transfer switch will throw, the truck will sense normal voltage and the charge will resume. The THD from your generator is good enough to run the appliances in your house and good enough to charge your truck (I don't think your truck even cares).

When the utility is up it doesn't matter when you charge. If the solar system is producing then energy from the array will go to the truck to the extent that the array output can meet the charging load and any short fall will come from the utility. Assuming you have 1 for 1 net metering and flat rates (a kWh is x ¢ any time of day and you get a credit of x ¢ for each kWh you send the utility) it doesn't matter when you charge. If the rates are time adjusted then it gets more complicated but it's probably not worth long nights with the Excel Solver trying to figure out the optimum strategy. If you drive the typical 10,000 miles a year that means about 5000 kWh electricity used which, at 10¢/kWh is $500.

Now if you want to be able to boast "My truck runs on fusion." or "My fuel cost for the truck is nothing per mile" then you want to see to it that your truck charges exclusively from the sun. To do that obviously you have to charge when the PV array is producing and you have to set the truck's charge rate to less than the array is producing. It looks like this.

Charging started at a little after noon at the maximu 11.5 kW. As the solar system was producing over 20 kW for most of that time and the total load, including the car was always less than that all the energy going to the car has to have come from the PV array. Exception was the brief interval at about 12:30 when a cloud went over and production dropped to 8 kW. In that interval some of the energy going to the car came from the utility.
Click to expand...

Fantastic! Thank you so much! You hit the nail on the head! I'm going to print that out and send it to my solar guy. Yes, our standard rates are 10 cents/KwH. Sometimes only 5 cents. June through Sept it goes to a demand rate for 5 hours per day only. I don't remember what the production is on my yet to be installed system, but they guarantee it in writing within 5% or they cut a check annually. I told him I'd just throw tarps over the panels until the system was paid off! LOL! I'll have to put a pencil to that one! We could be in a nuclear winter and they would cut the check every year.
Thanks again for taking the time to give such a detailed explanation.

 

[HaulingAss]

I don't remember what the production is on my yet to be installed system, but they guarantee it in writing within 5% or they cut a check annually. I told him I'd just throw tarps over the panels until the system was paid off! LOL! I'll have to put a pencil to that one! We could be in a nuclear winter and they would cut the check every year.

Not to be a party-pooper but you might want to read the fine print on your sales contract. I bet they would not be cutting you a check in the event of reduced production due to: a nuclear winter, volcanic ash plumes, etc.

 

[ajdelange]

Yes, our standard rates are 10 cents/KwH. Sometimes only 5 cents. June through Sept it goes to a demand rate for 5 hours per day only.

Do make sure you understand exactly how your tariff reads on this. Demand chargers ore based on the notion that while you may have an average demand of 4 kW if you ever draw 40 kW the power company must be able to provide that 40 kW and should be compensated for 40 kW service. For example my Jun electric bill showed that, net, I sent the power company, 2138 kWh. IOW I took no power from them. Looking back over the month I see this for the 17th:

We were heading out to the lake that day and so at a little before 6 AM I decided to run the SoC up to 90% for the trip and charged 7.4 kWh at the max rate (11.5 kW). The PV system was producing a paltry 300 W at that time and so most of the entire load, car and rest of the house, came from the power company. This was the most I drew from them in the entire billing period. The 30 minute average from the start of charging to the end of the highest bump on the top of the pedestal was 13.7 kW and my bill lists "Demand 13.2 kW". Note that's kW, not kWh. They have the right to charge me a lot for those kW. I don't remember what it is but they aren't charging for it. This may be because of new pro-solar laws passed here (Virginia) recently. If they charged what the old tariff allowed demand charges could be a major factor in my electric bill. Hence my advice to you to be sure you understand what your utility will do in this regard and takes steps to dodge demand charges when and if they are in effect. In Virginia demand charges were an attempt on the part of the utility to discourage solar installations. It sounds as if in your are they are intended to relieve demand during the "duck neck" part of the day.

The picture makes it clear that one way to dodge demand charges is to defer charging until later in the day i.e. dip into the abundant 161.4 kWh (I think that's my max ever) of solar collected on that day. Couldn't do that on th 17th as by the time the sun got cranking we were on the road. As the picture shows the solar could easily handle the Tesla and the house load with 5 kW to spare. Another strategy is to charge at lower than the maxiumum rate i.e. at 5 or 6 kW rather than 11.5. I tend to do that anyway reasoning that it's easier on the battery and I'm not in a hurry (unless leaving on a trip where, as we have seen, I just crank it back uo). If the demand charges are in the afternoon and there is a discount at night then charge at night.

I don't remember what the production is on my yet to be installed system, but they guarantee it in writing within 5% or they cut a check annually. I told him I'd just throw tarps over the panels until the system was paid off! LOL! I'll have to put a pencil to that one!

Yes, I think you'd better check the fine print on that one too. Five percent of what? You live in an area that averages 4.5 - 5 hrs effective full sun per day. If you install a 10 kW system you should collect 4.5*10*365 = 16425 to 5*10*365 = 18250 kWh per year. If your guy guarantees 95% of 10000 kWh/yr that's not really much of a guarantee but if he guarantees 95% of 18250 kWh he's a fool because there will be years when the system will produce less than that. I live in that same 4.5 - 5hr/da solar band. In it's first year of operation my system saw 3.19 hrs/da (71% of 4.5 hr/da). If he promised it would meet 95% of your load year round he is really crazy as, due to a combination of weather and the ecliptic, a system which covers 100% or more of your demand in summer may cover less than 20% of it in winter (depends on climate and how you heat and AC your house).

 

[drscot]

Not to be a party-pooper but you might want to read the fine print on your sales contract. I bet they would not be cutting you a check in the event of reduced production due to: a nuclear winter, volcanic ash plumes, etc.

No exclusions. Not even if I were to cover the panels with tarps, and they pay double the shortfall. Now a direct meteor strike is something neither one of us thought of though I must admit.

 

[tmeyer3]

My question is this: Does anyone have experience where a large blackout occurred and this was in the area of the Super Charger station? Does the Super Charger have it's own supply off the standard lines?

I know some SCs run off of solar, but do they have their own battery back up? If so, how many charges can you get from them? If everybody and there sister now drives an EV will they be going to charge up after a storm and deplete the battery reserve and suck up all the available energy just as people storm the groceries before a big storm and stock up on bread, milk and fried chicken?

Inquiring minds want to know.

Just drink the koolaide! You know you want to.

In all seriousness though. I haven't used the grid significantly in almost a year. I only charge at home. One day, energy will be solved, and it won't be with big power plants or generators.

This was yesterday with about a 40% charge on my model 3 long range.

Spoiler: Graphs

Spoiler: Numbers

 

[drscot]

Just drink the koolaide! You know you want to.

In all seriousness though. I haven't used the grid significantly in almost a year. I only charge at home. One day, energy will be solved, and it won't be with big power plants or generators.

This was yesterday with about a 40% charge on my model 3 long range.

Spoiler: Graphs

Spoiler: Numbers

I'm a newbie to solar. On average (if there is such a thing) , how long would a typical powerwall setup supply non rationed power to a "typical" home during a prolonged outage? 24 hours? 48? 72? A week? Assuming daytime solar production continued as usual, of course, but must also consider reductions from inclement weather too. I realize there are multiple variables. My setup will power my entire my home for as long there is a supply of natural gas, of which in all my 69 years, never once have I experienced a natural gas failure as long as the bill is paid. I THINK Tesla told me when I started exploring years ago that I would get about a 24 hours back up, which is not sufficient here, but don't hold me to that. Natural gas, although a fossil fuel, at least for backup power appears to be the most cost effective and reliable at present for those of us not on an unlimited budget. Few puritans board electric or wind up airplanes for air travel I'm sure. If they utilize an alternative to jet fuel (fossil fuel) then I'm all ears. I'd like to know what Leonardo DeCaprio and Al Gore power their private jets with for the record, and purchasing "carbon offsets" doesn't count. That's like the Pope selling indulgences for mortal sins.

 

[tmeyer3]

I'm a newbie to solar. On average (if there is such a thing) , how long would a typical powerwall setup supply non rationed power to a "typical" home during a prolonged outage? 24 hours? 48? 72? A week? Assuming daytime solar production continued as usual, of course, but must also consider reductions from inclement weather too. I realize there are multiple variables. My setup will power my entire my home for as long there is a supply of natural gas, of which in all my 69 years, never once have I experienced a natural gas failure as long as the bill is paid. I THINK Tesla told me when I started exploring years ago that I would get about a 24 hours back up, which is not sufficient here, but don't hold me to that. Natural gas, although a fossil fuel, at least for backup power appears to be the most cost effective and reliable at present for those of us not on an unlimited budget. Few puritans board electric or wind up airplanes for air travel I'm sure. If they utilize an alternative to jet fuel (fossil fuel) then I'm all ears. I'd like to know what Leonardo DeCaprio and Al Gore power their private jets with for the record, and purchasing "carbon offsets" doesn't count. That's like the Pope selling indulgences for mortal sins.

It completely depends on how you build it. It must be sized for what you intend it for. You can build it as a 24 backup, but you can also build it as a permanent grid replacement. I am still connected to the grid, but I provide more power to it than I use. Personally, power is critical for me as we power our own well; no electricity, no water. So when I contacted Tesla, I just explained that I never want to NEED the grid again and they just smiled at me and said, "you got it."
I do not have propane/gas of any kind.
All of my appliances are electric.

To get to your question: Without the EV charging, I would be more than able to power my family's home indefinitely. When I put 60kwh / day into the car, however, not so much. But even with the car, I would have no problem without the grid as powerwall automatically reserves 50% (it's a setting) for my home use in the case of a grid outage. Meaning, if I have no grid and I plug in my car, it will charge until the batteries are at 50%. Half of my powerwalls easily covers us for 2 days and a single sunny day can recharge from 0 to 100. In that event, no long road trips.

According to the app, the longest I've gone without power is 350 hours.

Since I do have the grid, I do use it when I need to charge the car a lot.

Spoiler: 2021 graphs

 

[ajdelange]

On average (if there is such a thing) , how long would a typical powerwall setup supply non rationed power to a "typical" home during a prolonged outage? 24 hours? 48? 72? A week?

...

I realize there are multiple variables.

I think you realize that this is an impossible question to answer. It depends on how you use electricity and on how mother nature supplies it to you. If you live in one of those all too rare places blessed with nearly continuous sunshine and modest seasonal demand variations it's not too hard to design a system that will supply power indefinitely most of the time but even in those places statistics will eventually catch up.

Think of a can with a tap at the bottom from which you draw water as you need it and which is filled (bt yy rain) at the top. You are asking how long is it before the can is empty. That depends on how fast the rain fills it and how fast you draw the water from the top.

As I can't answer the question for your particular circumstances the best I can do is present example data and let you draw your own conclusions. The following picture shows by how much solar production exceeded or fell short of demand at my place over the last few months.

The next picture assumes I have 3 Powerwalls and shows how much charge would be left in the bank at the end of the day

And this last one shows the same thing assuming 5 Powerwalls

When the bar is at 0 that means your Powerwall bank is fully discharged. As there is no utility, the Powerwalls shut down until enough sun returns to recharge them.

Perhaps rather than asking how long the system will run before discharging you should ask how many shutdowns are typical in a given time period. For the period shown in the pictures here there were 7 shutdowns with 3 Powerwalls and 4 with 3 in this 5 month period. We'd have to install 9 to get down to 3 and a whopping 17 to have no failures.

If I gave data for the 5 months around December the results would be very different as my demand is higher and solar production lower.

The message is that it all depends on the statistics of insolation in your area, the statisitics of how you use power and how many shutdowns you are willing to tolerate. And your goal in doing the analysis is plainly to determine how many Powerwalls to buy (not that Elon is actually selling them).

 

[2000prerunner]

Easier said than done.

It is getting much cheaper and there are still gov rebates for solar installations.

I think for 12k-20k, after rebate, you can have a crew (from who ever you decide to go with) come and install the whole system in less than a day (4-8Kw system) . The permitting process is also done by them but takes 1-3 months. Just finance that crap and get it over with. this isn't that complicated. Just go on yelp and see which solar installer is "good" call them up, sign a few documents and pay it off , or finance it. you do almost nothing. there is no secret. just say "i want that" and they will say "k, give us money and you got it bud".

yeah and about the sunny Sol Cal thing... it's true. Don't believe all the BS you hear from people about CA being a "hell hole with no freedoms ". Maybe don't live smack dab in the middle of down town LA right next to the staples center? Costal Orange county and many suburb in San Diego are basically the best places on earth to live. ski/surf/mountains/desert/city/Mexico all 2hr drive away. all this week in august it was mid 70's during the day. come winter time we can expect 60's .... saves range on the EV, no need to run heater/AC all the time.

 

[2000prerunner]

Thank you for that detailed explanation. I guess the term "cheap" is relative when it comes to generators, but Generac is an industry leader and the standby I bought at the top of their lineup, so I am pretty sure it is a quality unit. I paid $8500 installed for mine 5 years ago. With hurricane Sandy, Generacs were reported to run for 3 plus weeks without a hiccup provided they had natural gas and didn't get submerged. Mine just runs and runs and runs with power outages. Out here where the grid is less than premium it runs plenty, and nothing in my home over a 5 year period appears to have suffered from the power it generates, so I guess I'm safe. Of course, like I said (or intended to imply), I would only charge with the generator unintentionally during outages while asleep with automatic generator startup. Daytime solar panel "free" charging of course would be preferable. Nothing of course is "free", not even solar.

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.

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