5 ms·

At $793/KW, a 10KW system means no electric bill after 3 years. If the lifetime of the system is 20 years, that's at least 15 years of free electricity.

by chime 7y ago

reitzensteinm 7y ago
Only when someone else is subsiding the grid, which under net metering acts as a battery for free. That's not sustainable, especially as the price of solar drops making it a no brainier. The true cost of solar includes enough batteries to cut the grid connection, or buying and selling energy at market rates, which will involve generating many more kWhs than you consume. That said, we desperately need a carbon tax which would help swing the pendulum back even without net metering.
- chvid 7y ago
  Maybe they should buy some cheap electrical scooters as well ...
- chii 7y ago
  at 10kwh system means it basically falls in line with the average usage per household in the US (source https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 https://www.eia.gov/tools/faqs/faq.php?id=97&t=3) Therefore, this ought to be self-sufficient, if there's storage. Batteries cost extra, no doubt, so it's not "free" after 3 years, but would be pretty cheap if batteries can be amortized over their expected 25yr lifespan (assuming same batteries as telsa's).
  - reitzensteinm 7y ago
    You'd need to size the generation for your worst days, not the average over the year; if you're using any kind of electric heating (e.g. reverse cycle air con), and your generation is lower in the winter months, you'll drain your battery each day, and the overabundance in the summer months doesn't help you. Add in more solar panels for this, as well as the cost of a battery that can store a few days worth of power, and you're talking a substantially larger expense to cut the grid tie. However, the days of 100 year paybacks are clearly behind us if we're seriously doing back of the napkin math here. The progress in the field is impressive.
    - richardw 7y ago
      It might be cheaper to add a generator for exceptional days. Build the rest of the system for efficiency.
    - mattlondon 7y ago
      > your generation is lower in the winter months, you'll drain your battery each day, and the overabundance in the summer months doesn't help you. Certainly in the UK, you sell your over-generation back to the grid. This will offset the cost of buying from the grid on the days when your generation is lower than consumption. Certainly in the UK you may never get 100% net zero cost (not enough winter sunshine hours I suspect), but will help since most homes in the UK are heated via gas (as in gas, not petroleum)
- benj111 7y ago
  It depends where the 10kw figure comes from. If its been sized to sell enough power back to the grid to cover the grid tie then there's no subsidy. 10kw does sound high for the average Indian family.
  - reitzensteinm 7y ago
    I assumed parent was talking about the States, given both the size of the system and the electricity bill amount used for the payback calculation. If it's an overprovisioned system for India, then what I wrote should be disregarded.
- tomglynch 7y ago
  In Varanasi in India, many businesses have their own batteries as power cuts happen often enough that it's a necessity. I am using just a single city as an example, but potentially India already has much more battery installations than you expect (and than other countries with more reliable power sources).
  - 2sk21 7y ago
    And many homes have battery backup systems as well. However, they all use lead-acid batteries. There is a real opportunity for better battery technologies to be deployed in India.
    - ljf 7y ago
      My understanding (as limited as it is!) is that if space and weight are not an issue, then lead batteries provide a great deal of benefits today, especially when you can add to your system with 'dead' car batteries and the like. It is only where space and weight are an issue that you need to move to newer tech. I am fully prepared to be incorrect here though!
- blargmaster33 7y ago
  We need tax like we need cocaine injected into our eyeballs.
- jabl 7y ago
  This. Net metering is cool and all, but with the wrong grid fee structure it ends up as a subsidy to the already well off.
- ZeroGravitas 7y ago
  Most full accountings of solar's value to the grid show that homeowners with solar are subsidizing the grid (not the other way round) and other customers by providing power at peak usage times and being paid at rates that are averages and therefore below peak, and not accounting for wider costs/benefits: https://www.utilitydive.com/news/how-two-value-of-solar-studies-add-up-to-no-clear-value-of-solar/522892/ https://www.utilitydive.com/news/how-two-value-of-solar-stud...
  - reitzensteinm 7y ago
    Yeah, I've read a handful of studies that claim to show something like that, but every time you dig down in to the numbers there are glaring errors. Given that the Maryland study accounts for the benefit to the local economy (??), I'm not going to bother spending an hour on that. They've left their thumb on the scale. Typically solar does not provide much power at all during peak use, which is why the duck curve was coined. You can clearly see that homeowners with solar aren't subsidizing the grid, because laws needed to be passed in order to force utilities to accept the power. If someone hands you free money, you don't turn it down. Net metering was a handy subsidy to get solar started, but it's an obscene transfer of wealth from the poor to the rich in the long run. https://en.m.wikipedia.org/wiki/Duck_curve https://en.m.wikipedia.org/wiki/Duck_curve
    - ZeroGravitas 7y ago
      Many utilities are run on a cost plus basis which means they would be entirely economically rational to literally turn down free money, because it would reduce the amount of profit they could make. Also, the duck curve doesn't show peak use. The duck curve shows the peaks that are left after solar has been subtracted. Go find a duck curve, note that it will almost certainly be in springtime when overall demand is low. Then look up the yearly demand peak for that region. It will almost certainly be in the afternoon in the summer and will dwarf the duck curve peaks. So solar will be directly reducing the requirement to build out capacity (and further reducing utility profit potential/ saving everyone lots of money). Worst case scenario for the duck is to throw away a bit of solar power sometimes because other parts of the system need time to ramp. People clutch their pearls at this, just like they do at negative prices, but it's just nonsense with no logical basis. It's like complaining that buying a dozen eggs is wasteful if you only need 11. Yeah, but it's cheaper than buying 11 individual eggs so maybe just think of something to do with your "free" egg instead of complaining about a non-issue.

At $793/KW, a 10KW system means no electric bill after 3 years. If the lifetime of the system is 20 years, that's at least 15 years of free electricity.

by chime 7y ago

At $793/KW, a 10KW system means no electric bill after 3 years. If the lifetime of the system is 20 years, that's at least 15 years of free electricity.

reitzensteinm 7y ago

Only when someone else is subsiding the grid, which under net metering acts as a battery for free. That's not sustainable, especially as the price of solar drops making it a no brainier. The true cost of solar includes enough batteries to cut the grid connection, or buying and selling energy at market rates, which will involve generating many more kWhs than you consume. That said, we desperately need a carbon tax which would help swing the pendulum back even without net metering.

chvid 7y ago
Maybe they should buy some cheap electrical scooters as well ...
chii 7y ago
at 10kwh system means it basically falls in line with the average usage per household in the US (source https://www.eia.gov/tools/faqs/faq.php?id=97&t=3 https://www.eia.gov/tools/faqs/faq.php?id=97&t=3) Therefore, this ought to be self-sufficient, if there's storage. Batteries cost extra, no doubt, so it's not "free" after 3 years, but would be pretty cheap if batteries can be amortized over their expected 25yr lifespan (assuming same batteries as telsa's).
- reitzensteinm 7y ago
  You'd need to size the generation for your worst days, not the average over the year; if you're using any kind of electric heating (e.g. reverse cycle air con), and your generation is lower in the winter months, you'll drain your battery each day, and the overabundance in the summer months doesn't help you. Add in more solar panels for this, as well as the cost of a battery that can store a few days worth of power, and you're talking a substantially larger expense to cut the grid tie. However, the days of 100 year paybacks are clearly behind us if we're seriously doing back of the napkin math here. The progress in the field is impressive.
  - richardw 7y ago
    It might be cheaper to add a generator for exceptional days. Build the rest of the system for efficiency.
  - mattlondon 7y ago
    > your generation is lower in the winter months, you'll drain your battery each day, and the overabundance in the summer months doesn't help you. Certainly in the UK, you sell your over-generation back to the grid. This will offset the cost of buying from the grid on the days when your generation is lower than consumption. Certainly in the UK you may never get 100% net zero cost (not enough winter sunshine hours I suspect), but will help since most homes in the UK are heated via gas (as in gas, not petroleum)
benj111 7y ago
It depends where the 10kw figure comes from. If its been sized to sell enough power back to the grid to cover the grid tie then there's no subsidy. 10kw does sound high for the average Indian family.
- reitzensteinm 7y ago
  I assumed parent was talking about the States, given both the size of the system and the electricity bill amount used for the payback calculation. If it's an overprovisioned system for India, then what I wrote should be disregarded.
tomglynch 7y ago
In Varanasi in India, many businesses have their own batteries as power cuts happen often enough that it's a necessity. I am using just a single city as an example, but potentially India already has much more battery installations than you expect (and than other countries with more reliable power sources).
- 2sk21 7y ago
  And many homes have battery backup systems as well. However, they all use lead-acid batteries. There is a real opportunity for better battery technologies to be deployed in India.
  - ljf 7y ago
    My understanding (as limited as it is!) is that if space and weight are not an issue, then lead batteries provide a great deal of benefits today, especially when you can add to your system with 'dead' car batteries and the like. It is only where space and weight are an issue that you need to move to newer tech. I am fully prepared to be incorrect here though!
blargmaster33 7y ago
We need tax like we need cocaine injected into our eyeballs.
jabl 7y ago
This. Net metering is cool and all, but with the wrong grid fee structure it ends up as a subsidy to the already well off.
ZeroGravitas 7y ago
Most full accountings of solar's value to the grid show that homeowners with solar are subsidizing the grid (not the other way round) and other customers by providing power at peak usage times and being paid at rates that are averages and therefore below peak, and not accounting for wider costs/benefits: https://www.utilitydive.com/news/how-two-value-of-solar-studies-add-up-to-no-clear-value-of-solar/522892/ https://www.utilitydive.com/news/how-two-value-of-solar-stud...
- reitzensteinm 7y ago
  Yeah, I've read a handful of studies that claim to show something like that, but every time you dig down in to the numbers there are glaring errors. Given that the Maryland study accounts for the benefit to the local economy (??), I'm not going to bother spending an hour on that. They've left their thumb on the scale. Typically solar does not provide much power at all during peak use, which is why the duck curve was coined. You can clearly see that homeowners with solar aren't subsidizing the grid, because laws needed to be passed in order to force utilities to accept the power. If someone hands you free money, you don't turn it down. Net metering was a handy subsidy to get solar started, but it's an obscene transfer of wealth from the poor to the rich in the long run. https://en.m.wikipedia.org/wiki/Duck_curve https://en.m.wikipedia.org/wiki/Duck_curve
  - ZeroGravitas 7y ago
    Many utilities are run on a cost plus basis which means they would be entirely economically rational to literally turn down free money, because it would reduce the amount of profit they could make. Also, the duck curve doesn't show peak use. The duck curve shows the peaks that are left after solar has been subtracted. Go find a duck curve, note that it will almost certainly be in springtime when overall demand is low. Then look up the yearly demand peak for that region. It will almost certainly be in the afternoon in the summer and will dwarf the duck curve peaks. So solar will be directly reducing the requirement to build out capacity (and further reducing utility profit potential/ saving everyone lots of money). Worst case scenario for the duck is to throw away a bit of solar power sometimes because other parts of the system need time to ramp. People clutch their pearls at this, just like they do at negative prices, but it's just nonsense with no logical basis. It's like complaining that buying a dozen eggs is wasteful if you only need 11. Yeah, but it's cheaper than buying 11 individual eggs so maybe just think of something to do with your "free" egg instead of complaining about a non-issue.