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I paid ~15k to install solar in 2019. After tax rebates it was ~11k. I’m generating ~12MWh per year. My break even period is less than 5 years. I’m based out o

I paid ~15k to install solar in 2019. After tax rebates it was ~11k. I’m generating ~12MWh per year. My break even period is less than 5 years. I’m based out of California, and generate excess energy. My electric bill is now just ~$100/year.

mesarvagya 4y ago
~12MWh or ~12KWh ?
- drdrey 4y ago
  12kWh is what a typical rooftop solar system can produce in a day so OP's number of 12MWh checks out for a whole year
perfectstorm 4y ago
if you generate excess energy, can you store it for a later time when you need more energy (presumably summer time)?
- pkaye 4y ago
  You would need batteries which are quite expensive at this time.
  - mnw21cam 4y ago
    There are no sensible storage methods that would allow you to store enough energy from summer to make any reasonable contribution towards winter. Batteries a great for powering your house for a few days. Not really beyond that. Unless you buy a ridiculous amount of batteries.
    - edmundsauto 4y ago
      Batteries are also great for using at night!
- asdff 4y ago
  While you wait decades for home battery storage technology to improve, you can make a water battery in the meantime with a few things from the hardware store. https://hackaday.com/2021/10/08/power-your-home-with-a-water-battery/ https://hackaday.com/2021/10/08/power-your-home-with-a-water...
  - byyll 4y ago
    You have to be joking, right? That's a 55 gallons of water as a battery that require 5.5 hours to charge and store 3.9 Wh of energy. Not enough to even power a 10W LED lamp for half an hour. A 10,000 mAh power bank is 37Wh.
  - AdamTReineke 4y ago
    This system only had enough power to run a small light, IIRC.
  - 0cf8612b2e1e 4y ago
    You can buy a residential battery today that provides real value. The limitation on batteries is for grid scale supply.
- mrits 4y ago
  It's a lot more efficient to sell back to the power company. I'd be more comfortable with having a dual fuel generator for apocalyptic situations vs a bunch of batteries.
- Rebelgecko 4y ago
  Some (all?) electric companies in CA do net metering, where you can sell them your excess electricity at any time and storage essentially becomes their problem.
- gpm 4y ago
  > presumably summer time Assuming you have batteries, you discharge and charge them on a daily cycle, not a yearly cycle, to make the most money/have the most benefit. There are predictable time of day based troughs and peaks in the price that you can take advantage of.
- bushbaba 4y ago
  Why would I? I’m on NEM 2.0. The grid is my “battery”. Every KWh I generate that isn’t used is sent back to the grid. In exchange I get an IOU for the equivalent $/KWh price during that time. This is the retail $/KWh which includes transmission costs.
Aperocky 4y ago
Do you have a battery or are the excess directly dumped to grid?
- bushbaba 4y ago
  Excess sent to the grid using the NEM 2.0 TOU-C rate plan.
Dwolb 4y ago
Have you experienced any grid power outages where your solar panels saved your day?
- cheald 4y ago
  Solar won't keep you online through a power outage. The inverter is required by law to cut power from solar panels when there is not power from the grid, so as to avoid feeding electricity back into the grid lines (which technicians may be working on!) - this is known as anti-islanding protection. If you want to be online through a grid outage you need a battery array.
  - CTmystery 4y ago
    From a circuit perspective, it seems trivial to open a switch back to the grid to prevent grid-feed, while still feeding the internal circuit that is the house. Can you help me understand why this is hard?
    - cheald 4y ago
      It's doable, but it requires a bunch of extra expensive equipment. Most people that want to accomplish that goal just install a battery array instead, since you're spending the money and it also gets you power coverage when the sun isn't shining. But the point stands that the typical grid-tied solar system just turns off when the grid goes down.
    - aiProgMach 4y ago
      It's not hard. There is type of inverters that called "Hybrid inverter", I have one that can keep power off-grid or on-grid or even on-grid in import mode only (so only import any needed power without exporting...), and it can work off-grid even without battery (from solar) but that is not recommended unless you know that your load is much smaller than the solar output, even small lead-acid battery can mitigate this issue. The way the inverter work is that when the grid goes off it will automatically switch the power export off and keep the load running from solar and/or battery in isolated mode.
    - 4y ago

mesarvagya 4y ago

~12MWh or ~12KWh ?

drdrey 4y ago
12kWh is what a typical rooftop solar system can produce in a day so OP's number of 12MWh checks out for a whole year

perfectstorm 4y ago

if you generate excess energy, can you store it for a later time when you need more energy (presumably summer time)?

pkaye 4y ago
You would need batteries which are quite expensive at this time.
- mnw21cam 4y ago
  There are no sensible storage methods that would allow you to store enough energy from summer to make any reasonable contribution towards winter. Batteries a great for powering your house for a few days. Not really beyond that. Unless you buy a ridiculous amount of batteries.
  - edmundsauto 4y ago
    Batteries are also great for using at night!
asdff 4y ago
While you wait decades for home battery storage technology to improve, you can make a water battery in the meantime with a few things from the hardware store. https://hackaday.com/2021/10/08/power-your-home-with-a-water-battery/ https://hackaday.com/2021/10/08/power-your-home-with-a-water...
- byyll 4y ago
  You have to be joking, right? That's a 55 gallons of water as a battery that require 5.5 hours to charge and store 3.9 Wh of energy. Not enough to even power a 10W LED lamp for half an hour. A 10,000 mAh power bank is 37Wh.
- AdamTReineke 4y ago
  This system only had enough power to run a small light, IIRC.
- 0cf8612b2e1e 4y ago
  You can buy a residential battery today that provides real value. The limitation on batteries is for grid scale supply.
mrits 4y ago
It's a lot more efficient to sell back to the power company. I'd be more comfortable with having a dual fuel generator for apocalyptic situations vs a bunch of batteries.
Rebelgecko 4y ago
Some (all?) electric companies in CA do net metering, where you can sell them your excess electricity at any time and storage essentially becomes their problem.
gpm 4y ago
> presumably summer time Assuming you have batteries, you discharge and charge them on a daily cycle, not a yearly cycle, to make the most money/have the most benefit. There are predictable time of day based troughs and peaks in the price that you can take advantage of.
bushbaba 4y ago
Why would I? I’m on NEM 2.0. The grid is my “battery”. Every KWh I generate that isn’t used is sent back to the grid. In exchange I get an IOU for the equivalent $/KWh price during that time. This is the retail $/KWh which includes transmission costs.

Aperocky 4y ago

Do you have a battery or are the excess directly dumped to grid?

bushbaba 4y ago
Excess sent to the grid using the NEM 2.0 TOU-C rate plan.

Dwolb 4y ago

Have you experienced any grid power outages where your solar panels saved your day?

cheald 4y ago
Solar won't keep you online through a power outage. The inverter is required by law to cut power from solar panels when there is not power from the grid, so as to avoid feeding electricity back into the grid lines (which technicians may be working on!) - this is known as anti-islanding protection. If you want to be online through a grid outage you need a battery array.
- CTmystery 4y ago
  From a circuit perspective, it seems trivial to open a switch back to the grid to prevent grid-feed, while still feeding the internal circuit that is the house. Can you help me understand why this is hard?
  - cheald 4y ago
    It's doable, but it requires a bunch of extra expensive equipment. Most people that want to accomplish that goal just install a battery array instead, since you're spending the money and it also gets you power coverage when the sun isn't shining. But the point stands that the typical grid-tied solar system just turns off when the grid goes down.
  - aiProgMach 4y ago
    It's not hard. There is type of inverters that called "Hybrid inverter", I have one that can keep power off-grid or on-grid or even on-grid in import mode only (so only import any needed power without exporting...), and it can work off-grid even without battery (from solar) but that is not recommended unless you know that your load is much smaller than the solar output, even small lead-acid battery can mitigate this issue. The way the inverter work is that when the grid goes off it will automatically switch the power export off and keep the load running from solar and/or battery in isolated mode.
  - 4y ago