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I certainly understand that. But running PVWatts and comparing my hourly usage I only lightly overproduce. I looked at August 15th and at noon I used 4.5kWh and the anticipated production from noon to 1PM on a typical August 15th in my area is 4.8kWh. In general, my solar will produce what I use during the day and not much more. This doesn't leave much excess to go to PW or grid which is why I may end up switching to a free nights plan.
Fair enough, but if you are expecting to be consuming solar power as it is generated you need to use it as it is generated, which isn’t an average. So in your example from noon to 1PM your solar system might produce 4.8kWh. This means that assuming there are no clouds the system will be producing 4.8kW for one hour. However, even though your house may average 4.5kWh, that doesn’t necessarily mean that it will draw 4.5kW for one hour.
Instead your house might draw 2kW for 30 minutes, and then your air conditioner might come on and your house will then draw 7kW for 30 minutes. Over that hour your house would have averaged 4.5kWh and even though your solar system produced 4.8kWh over that same time period you only would have been able to directly use 3.4Wh. You would have sent 1.4kWh to the grid (during the first half hour) and you would have needed to draw 1.1kWh from the grid (during the second half hour)
As long as you have net metering, then this is not a problem, since the net will be .3kWh to the grid, but it’s my understanding that there aren’t a lot of net metering options in TX.
With a powerwall the system could have used that excess 1.4kWh that you would have sent to the grid to charge the powerwall during the first 30 minutes, then pulled back 1.1kWh during the next 30 minutes.
The thing to remember is that (other than minor efficiency losses) the powerwalls aren’t a net consumer or a net generator of power. They won’t allow you to get more power from your solar system and you won’t need to install a bigger solar system just to use powerwalls. They simply allow you to take the power that you are generating and use it at a different time. This is helpful because solar power can only be generated during certain times of the day and often is generated in excess during those times.
Obviously that example is a bit oversimplified, but the point is that your home usage fluctuates a lot when you consider things like air conditioner or refrigerator compressors cycling on and off and other appliances being used. Even things like electric ovens and driers will cycle power to their heating elements when they are running, so you can’t really look at averages if you’re trying to figure out how much solar power you can directly consume. You need to consume that power in the moment that it is produced or use it to charge a powerwall or send it back to the grid.
