Tesla Powerwall

After our first full calendar month since we moved in, we can share our thoughts and experiences with our Solar Panels and the Tesla Powerwall.

It was May (probably the best month of the year for solar energy, at least in the northern hemisphere) and of course, we really need to wait a full year to have the full picture.

Here is an analysis of a really sunny day – 27th May

  • Colour coding for the screenshot below is:
    • Green is the electricity which the system produced (almost no clouds that day)
    • Blue is the own-produced electricity we used
    • Red is the electricity we bought from the grid (not very much!)
  • 25 kWh electricity was produced that day
    • 11.8 kWh of which we used ourselves
    • 13.4 kWh of which was exported (some of the ‘exported’ electricity will have been used by out heating/hot water system which is on a different electricity meter, but it was a hot day with no heating required, so most of it would have been sold to the grid!)
  • Since almost all of our electricity usage on that day was at a time when there wasn’t much electricity being generated (we were not home at lunchtime!), 53% of our usage came from the battery, rather than directly from the panels. On a day like this, the battery clearly makes a huge difference to how much electricity we bought that day.


Other statistics for May:

  • Despite a wet start to the month (almost the first week there was no sun), on 21 out of 31 nights, the battery had enough charge to last all the way through the night.
  • Between 8:00 am on 20th May and 5:30 am on 31st May (11 days), the battery was almost never flat, with only an hour or two on a couple of days where it didn’t quite make it through the night and went flat just before the solar panels were producing again.
  • In total (including the heating/hot water system) during May:
    • We used 559 kWh in total
    • We bought 255 kWh from the grid
    • We sold 163 kWh to the grid
    • We used just 92 kWh more than the system produced.

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