Tesla Model S waffling

[JST]

Originally Posted by lemming

i think if you live in the sun belt (you do) and if you can give power back to the grid, instead of needing to store it in batteries, and then get it back, that's ideal --as long as you're making a serious commitment with significant financial outlay to support a 30kW/day system. otherwise it's just like a prius: i.e. all for show.

the nerd thread reminded me that you lose 15% pushing to batteries and another 15% from batteries back to car/home.

It's not all for show. You don't have to offset 100 percent of your energy usage to derive some benefit from solar. Whether you will derive *enough* benefit from solar to make it make sense financially is an individual call, but it's one that you can only make after you run the numbers for your particular circumstance.

That said, there is an emotional/political component to the decision that many people make on solar. It's not just about hard numbers, it's also about committing to GHG reduction. That might qualify as being "just for show," but it's an additional factor for most people, not the only one.

The threads you referenced that talk about how to make an off-grid solar setup large enough to charge an 85kWh car battery are really an extreme case. Very few people need or want that; most people that put in solar do grid-tied systems that allow them to reduce their purchase from the grid, but aren't intended to fully replace the grid.

Bottom line? You can *offset* your total energy usage using a much smaller and simpler solar array than you would need to *supply* your total energy usage.

[lemming]

Originally Posted by JST

It's not all for show. You don't have to offset 100 percent of your energy usage to derive some benefit from solar. Whether you will derive *enough* benefit from solar to make it make sense financially is an individual call, but it's one that you can only make after you run the numbers for your particular circumstance.

That said, there is an emotional/political component to the decision that many people make on solar. It's not just about hard numbers, it's also about committing to GHG reduction. That might qualify as being "just for show," but it's an additional factor for most people, not the only one.

The threads you referenced that talk about how to make an off-grid solar setup large enough to charge an 85kWh car battery are really an extreme case. Very few people need or want that; most people that put in solar do grid-tied systems that allow them to reduce their purchase from the grid, but aren't intended to fully replace the grid.

Bottom line? You can *offset* your total energy usage using a much smaller and simpler solar array than you would need to *supply* your total energy usage.

that's mediocre IQ thinking though.

when you think about it rationally, the #1 and #2 producers of emissions are powerplants and then the transportation backbone of the country and #3 is homes.

start there.

if we merely improved the heating/cooling efficiency of houses, that's money far better spent than solar whatever. solar at this point is like buying a newton device from Apple. good intent, poor execution. if it makes an early adopter feel better? okay. but relevance? none.

if we, for example were able to legislate tougher emissions for all aforementioned waste streams as well as shamed all people in inefficient homes, it would impact the world for the better, for the next generation.

this token solar thing is just like buying a Tesla. it's an issue for the 1% and i do not have tolerance for that righteousness being disconnected from reality.

[JST]

Originally Posted by lemming

that's mediocre IQ thinking though.

when you think about it rationally, the #1 and #2 producers of emissions are powerplants and then the transportation backbone of the country and #3 is homes.

start there.

if we merely improved the heating/cooling efficiency of houses, that's money far better spent than solar whatever. solar at this point is like buying a newton device from Apple. good intent, poor execution. if it makes an early adopter feel better? okay. but relevance? none.

if we, for example were able to legislate tougher emissions for all aforementioned waste streams as well as shamed all people in inefficient homes, it would impact the world for the better, for the next generation.

this token solar thing is just like buying a Tesla. it's an issue for the 1% and i do not have tolerance for that righteousness being disconnected from reality.

You are mixing individual actions with public policy prescriptions. Are there better ways to tackle GHG emissions on a broad scale than having everyone individually decide to install solar panels? Sure.

Are there things you can do to reduce your energy usage that are more effective than offsetting that usage by installing solar? Eh, on this one I am not so sure. For example, in my case I already have pretty efficient appliances, and my HVAC systems are also pretty good. I could insulate my house more effectively, but I've already got decent insulation in the attic, so a real improvement would require ripping out my interior walls and putting insulation there. I am betting that would cost at least as much as a 10kW solar system.

[lemming]

Originally Posted by JST

Are there things you can do to reduce your energy usage that are more effective than offsetting that usage by installing solar? Eh, on this one I am not so sure. For example, in my case I already have pretty efficient appliances, and my HVAC systems are also pretty good. I could insulate my house more effectively, but I've already got decent insulation in the attic, so a real improvement would require ripping out my interior walls and putting insulation there. I am betting that would cost at least as much as a 10kW solar system.

Everything that you listed there is, from a by the numbers analysis, going to contribute to the bottomline more so than solar panels, given the state of the art currently for that technology.

home efficiency first, and you're covering that.

solar paneling, to hit the level where it's useful, is a 1 percenter endeavor, just like the Tesla model S. so the two ideas fit like hand in glove. it's just that neither really make an impact whatsoever, other than the self-satisfaction.

30,000 cars at 100,000USD in a pool of 16million vehicles, of which 60-65% are light trucks or trucks --irrelevant.

10kW/day solar system can barely meet the needs of a model S with the uprated 85kW system, and you're taking a system that starts with 21% efficiency, times 85% to save the energy, times 85% to spit it back out for the car. that ends up being 15% efficiency --so I guess the question is, is starting out with 10kW enough or do you need to triple that, to account for the line losses?

I don't know the answers to these questions because i'm too practical for something like this and it just doesn't appeal to me.

[ZBB]

Originally Posted by lemming

10kW/day solar system can barely meet the needs of a model S with the uprated 85kW system, and you're taking a system that starts with 21% efficiency, times 85% to save the energy, times 85% to spit it back out for the car. that ends up being 15% efficiency --so I guess the question is, is starting out with 10kW enough or do you need to triple that, to account for the line losses?

Just to clarify -- a 10kW solar system is the max output it can do at any point in time. To get the average daily output you have to multiply that by the # of "solar hours" avail. For me, we have just over 6.5 solar hours avail on average throughout the year, so a 10kW system would generate 65kW each day (but less in winter and more in summer).

Generating 10kW/day would be a very small rooftop solar system -- 1.5kW here, which is "only" 6 panels... Interestingly, here's a DIY package (i.e. everything but install) -- about $2500 before federal rebates.
https://www.anapode.com/products/100...Module_Kit_DIY

The same site has larger kits. a 10kW system is about $20k -- with 40 panels, and every 5kW above that adds another 20 panels and ~$10k. Before options of course

Traditionally, we had utilities that provided power only through the grid. Off-grid was rare (although my family had a ranch that was off-grid as a kid that had 2 diesel generators to power the place -- and we turned them off at night and used flashlights and fireplaces...). But what's happening now is a big move to "distributed power" -- basically generating power at the same place it is used. For residential, solar is the most common, but there are also some residential wind generators avail, and we've had multiple discussions here about backup generators.

As for why do solar -- forgetting the "green" reasons, it all comes down to the cost to obtain enough electricity for your house. In my case, we pay our utility ~$2500 a year for electricity. Based on above, I could put in a $20k solar system, pay another $5k for installation and effectively pre-pay most of our electricity for the next 10 years (and the system would still be under warranty for another 10-15 years). Or we could lease a solar system and pay SolarCity or one of the other lease providers each month a little bit more. We'd still pay some utility bill -- since in AZ the grid-tie rules dissuade over-producing (you want to be a net buyer from the grid...).

Additionally, rooftop solar is not a 1% thing. Come out here to AZ sometime and drive around neighborhoods. Solar may only be on a few percent of houses, but its all over town -- even on houses that cost $100k...

[lemming]

Originally Posted by ZBB

Just to clarify -- a 10kW solar system is the max output it can do at any point in time. To get the average daily output you have to multiply that by the # of "solar hours" avail. For me, we have just over 6.5 solar hours avail on average throughout the year, so a 10kW system would generate 65kW each day (but less in winter and more in summer).

Generating 10kW/day would be a very small rooftop solar system -- 1.5kW here, which is "only" 6 panels... Interestingly, here's a DIY package (i.e. everything but install) -- about $2500 before federal rebates.
https://www.anapode.com/products/100...Module_Kit_DIY

The same site has larger kits. a 10kW system is about $20k -- with 40 panels, and every 5kW above that adds another 20 panels and ~$10k. Before options of course

Traditionally, we had utilities that provided power only through the grid. Off-grid was rare (although my family had a ranch that was off-grid as a kid that had 2 diesel generators to power the place -- and we turned them off at night and used flashlights and fireplaces...). But what's happening now is a big move to "distributed power" -- basically generating power at the same place it is used. For residential, solar is the most common, but there are also some residential wind generators avail, and we've had multiple discussions here about backup generators.

As for why do solar -- forgetting the "green" reasons, it all comes down to the cost to obtain enough electricity for your house. In my case, we pay our utility ~$2500 a year for electricity. Based on above, I could put in a $20k solar system, pay another $5k for installation and effectively pre-pay most of our electricity for the next 10 years (and the system would still be under warranty for another 10-15 years). Or we could lease a solar system and pay SolarCity or one of the other lease providers each month a little bit more. We'd still pay some utility bill -- since in AZ the grid-tie rules dissuade over-producing (you want to be a net buyer from the grid...).

Additionally, rooftop solar is not a 1% thing. Come out here to AZ sometime and drive around neighborhoods. Solar may only be on a few percent of houses, but its all over town -- even on houses that cost $100k...

walk me through the math --so it's 10kW/h? or 10kW/second? I'm just trying to understand the throughput or total net for a typical AZ day.

if it's 10kW/hr, and it's 85kW per day, and you are on the grid (in other words, give that to the grid and take back what you need cost free in order to preclude the need for on-site battery storage), you're still net 17kW per day (21% efficiency) which is awesome. is that math good?

understanding this helps me.

[ZBB]

Originally Posted by lemming

walk me through the math --so it's 10kW/h? or 10kW/second? I'm just trying to understand the throughput or total net for a typical AZ day.

if it's 10kW/hr, and it's 85kW per day, and you are on the grid (in other words, give that to the grid and take back what you need cost free in order to preclude the need for on-site battery storage), you're still net 17kW per day (21% efficiency) which is awesome. is that math good?

understanding this helps me.

Systems are rated in 10kW -- thats a power rating Thats like saying a car has 300HP.

Where kWh (or kilowatt hours) comes into play is when you calculate the power rating over time. A 10kW system can generate 10kWh in 1 hour, or 40kWh in 4 hours (4*10).

Similar a 100W light bulb is the power rating of the bulb. The energy used is the power rating multiplied by time -- so a 100W bulb would use 100W in 1 hour and 1kW in 10 hours...

[lemming]

Originally Posted by ZBB

Systems are rated in 10kW -- thats a power rating Thats like saying a car has 300HP.

Where kWh (or kilowatt hours) comes into play is when you calculate the power rating over time. A 10kW system can generate 10kWh in 1 hour, or 40kWh in 4 hours (4*10).

Similar a 100W light bulb is the power rating of the bulb. The energy used is the power rating multiplied by time -- so a 100W bulb would use 100W in 1 hour and 1kW in 10 hours...

i found the information that made sense to me.

The only caveat that I cannot understand, because it's so sales-y, is if a system rated for 10kW is net or gross? so the actual solar energy generated is 2.1kW or 10kW?

I get that this could power an average home (another fudge factor), but the real question (and we know this is an issue) is if the system can generate the amperage-gated power for adequate charging of a Tesla S. obviously 110V charges a Tesla, but it ain't pretty. so the next question I have is about amps.

[ZBB]

Voltage x Amps = Watts

I charge my tesla at 240V and 40A. 240x40 is just 9,600W or just under 10kW

If I plug into a 120V outlet, most of those are on 15A circuits, which can output 12A continuous (80% of rated is the continuous draw allowed by code, and Tesla falls under continuous draw.). So I get 1.4kW output at 120.

I use 15-20 kWh most days, so at 240V charging it takes 1.5-2 hours and at 120v would take 10-13 hours to charge...

[lemming]

Originally Posted by ZBB

Voltage x Amps = Watts

I charge my tesla at 240V and 40A. 240x40 is just 9,600W or just under 10kW

If I plug into a 120V outlet, most of those are on 15A circuits, which can output 12A continuous (80% of rated is the continuous draw allowed by code, and Tesla falls under continuous draw.). So I get 1.4kW output at 120.

I use 15-20 kWh most days, so at 240V charging it takes 1.5-2 hours and at 120v would take 10-13 hours to charge...

so when reduced to practice, if you're on-grid, that's simple because it's grid electricity fed back to your house (AC voltage is easy to figure out)

would most people in AZ be on-grid then?