Generators ( which one to buy )

[sfsuphysics]

So if my solar isnt that large and it takes a few days to total recharge the wall would it be feasible to get the wall? My roof could only fit a 3.5kw solar systems figure it would take a few days to charge the powerwall and only want to use it during emergencies outtages.

The newest(?) powerwall has a 14kWh capacity, so with 3.5kW of solar panels it is feasible you could charge it to capacity in a single day, maybe a couple days if it's winter and you're not producing peak.

 

[JVU]

So if my solar isnt that large and it takes a few days to total recharge the wall would it be feasible to get the wall? My roof could only fit a 3.5kw solar systems figure it would take a few days to charge the powerwall and only want to use it during emergencies outtages.


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You can see and download your electricity usage from PGE’s website and run the numbers to see:
1. How much electricity you use normally per day, and estimate how much you would use if you turned off everything nonessential.
2. How much you use minus how much your solar system would produce per day (this varies a lot by time of year) is the differential your battery would have to cover.
3. This will tell you how much you will be drawing down against the 13.5 kWh stored in one PW2 per day and therefore how long it would last you in a complete and extended outage.

Also there’s a cool feature with the PW that it goes into “Storm Watch” mode when there is a known risk to the electricity system in your area, it has been reliably triggered by each of the PGE planned outages. In this mode, it will charge your PW quickly from the grid whenever possible to leave you with as full a battery as possible (not just charging with solar like usual). This means that if your battery and solar system could last you for 3 days, you could have 3 days down, then half a day up, then 3 days down and still be ok.

Another fun feature with the PW app from Tesla is that it shows you in real time how electricity is flowing from solar, from/to grid, from/to battery, to house use. Helps you to optimize use and load when needed.

 

[Flagg37]

You can see and download your electricity usage from PGE’s website and run the numbers to see:
1. How much electricity you use normally per day, and estimate how much you would use if you turned off everything nonessential.
2. How much you use minus how much your solar system would produce per day (this varies a lot by time of year) is the differential your battery would have to cover.
3. This will tell you how much you will be drawing down against the 13.5 kWh stored in one PW2 per day and therefore how long it would last you in a complete and extended outage.

Also there’s a cool feature with the PW that it goes into “Storm Watch” mode when there is a known risk to the electricity system in your area, it has been reliably triggered by each of the PGE planned outages. In this mode, it will charge your PW quickly from the grid whenever possible to leave you with as full a battery as possible (not just charging with solar like usual). This means that if your battery and solar system could last you for 3 days, you could have 3 days down, then half a day up, then 3 days down and still be ok.

Another fun feature with the PW app from Tesla is that it shows you in real time how electricity is flowing from solar, from/to grid, from/to battery, to house use. Helps you to optimize use and load when needed.

A neighbor showed me the app. I thought it was really cool. You could switch between drawing power from the grid or battery with the touch of a button.

 

[sfsuphysics]

But you can't put power back on the grid (sell back) at least in California because PG&E will be the ONLY one to sell cheap power for exorbitant prices.

 

[JVU]

But you can't put power back on the grid (sell back) at least in California because PG&E will be the ONLY one to sell cheap power for exorbitant prices.

You can’t put power from your battery directly to the grid, because they are trying to avoid having people game the system by loading the battery at night when TOU rates are cheap and dumping it back on the grid during peak hours which are about 4x as expensive. In my opinion they should still allow this since it would decrease reliance on expensive gas-fired peaker plants in the afternoon, but that is a different discussion.

But the combination of solar and battery DOES actually allow you to put more electricity from your solar back on to the grid at peak prices than you would with solar alone. Your battery charges up to max from solar while electricity is relatively cheap in the morning. When prices are peak and the sun is still out in the afternoon, your battery powers your home while 100% of the solar goes to the grid for max credit. If you had solar but no battery, solar would cover your home first and if any is left over it would go to the grid. The difference is substantial, enough to help pay off the batteries in a relatively short time (depending on use and settings).

 

[JVU]

Example of what I mean. PW is powering the house, allowing all 5 kW made by solar to go the grid for peak rates. Without it, 3.2 kW would be used by the house and only 1.8 kW would be going to the grid.

It’s not exactly the same as selling from the PW to grid, but it’s a similar net effect.

 

[sfsuphysics]

You can’t put power from your battery directly to the grid, because they are trying to avoid having people game the system by loading the battery at night when TOU rates are cheap and dumping it back on the grid during peak hours which are about 4x as expensive. In my opinion they should still allow this since it would decrease reliance on expensive gas-fired peaker plants in the afternoon, but that is a different discussion.

Yeah I get the reasoning behind it, but like you I don't agree with it.

PG&E simply wants to keep things centralized so they don't have to give up power (no pun) in their controlling of the power grid. Keep rocking those 19th century solutions for a 21st century world because it makes them the most money in the long run.