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Performance Self-Powered and Solar Offset graphs don't seem right?

New Solar and PW (2 PW) customer questioning the accuracy of the performance graphs. I am getting marginal Solar from my new installation because of winter conditions. In a 24 hour period, I am using PW and Solar approximately 13 hours. Solar from 8 am until 4 pm, and then PW's between 4 pm and 9pm. Nothing is returned to the grid, and the PW's are only getting charged to a 40% capacity during the day hence they stop producing at 9pm.

My graphs Self-powered shows 69%, and the offset shows 71% energy offset.

Based on the above those reports can not be right with 13 hours of Solar, and Battery, and 11 hours of Grid.

It is more like 50/50.

How does Tesla generate these numbers for these reports?



  • Set it to cost savings instead of self-powered. Cost Savings will first use all your solar for battery charging. Then only after the batteries are charged will solar then be used for your house with excess going back to the grid.

    On self powered all solar first goes to the house with excess going to the battery.
  • I think self powered and energy offset are calculated using kW used and not time so your measurements seem reasonable (assuming lower kW utilization at night). Self power being mix of kW from all sources used by home in day and energy offset being solar kW (irrespective of how it's used) compared to home kW in a day.
  • In order to get a real performance assessment - first get your Powerwalls fully charged. In the winter with shorter days and lower sun angle, it may take a full day of solar output to get this done. Easiest way is to achieve this is to set as backup only. You will get to 100% change.
    First day after you are fully charged - then start your management experimentation and assessments.
    In terms of the assessments of performance - think about your usage patterns and when they occur - not just hours. If you are drawing from the grid 9pm to 7am - you are almost certainly using very little power - you are likely asleep - so total hours is not the appropriate assessment. Start thinking in terms of kWHrs...the number of hours at whatever rate of usage. Your kWHrs will likely be highest for both production and consumption during daylight hours.
  • Also what Jones stated. Both Cost Savings and Backup only will use all solar to charge the battery. The difference is in backup only, once your batteries are charged they will not be used by the house unless there is an outage. In cost savings the batteries will be used to power the house during the peak TOU hours and then the house will go back to grid usage after the peak hours are complete.
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