Battery, part 1

This post is literally just a teaser.

The solar install was to include a battery, but it has taken months to arrive. Finally it is fixed to the wall - that is it for part 1, bolted to the wall.

It is Tesla Powerwall with 13½kWh usable storage, with 5kW charge/discharge rate.

Later this week Some time next week, it will be wired up, including a "gateway" to allow me to run off grid during power cuts.

Should be fun, watch this space.

But yes, planning to explain what it is, how much, what it does, how the wiring works, how it works with the solar panels, the app, the API, the tariff I end up, etc...


  1. Hugely satisfying running your house 'off grid' for the majority of the day. I force topup my battery overnight using cheap electric and then pull nearly nothing from the grid during the day. Bill for the past two months electric - Total consumption 1072.4kWh @ 6.08p/kWh £65.22 (Battery+PV+EV+House+A/C) Includes all driving as well!!

  2. Congrats on managing to get one of those - they're like hens' teeth due to the demand!

    I suspect you'll want to add (subject to DNO approval) a second one given how much energy your house uses.

    Since your Powerwall is installed outdoors, you should be aware that they don't like it cold! On cold but sunny mornings last winter, our PW took quite a while to warm up enough so the batteries could absorb the full output of our solar panels, leading to exporting valuable power. Our PW is installed within a detached garage which is generally a few degrees warmer than outside, so your location could exacerbate the issue. There have been a few firmware updates since last winter, with the most recent claiming to improve cold weather performance...

    The backup feature is useful, though going off-grid is not as seamless as a UPS. You may see as much as a couple of seconds delay for the PW to restore power, so a UPS for sensitive loads is still required. Note, however, that the PW may raise the AC frequency to signal solar inverters to curtail solar production and/or to stop EV chargers. The rise in frequency can cause some UPSs to switch to battery, even though 240 volts a/c is still available!

    Finally, and knowing your penchant for monitoring stuff, you'll be pleased to know that you can extract a whole wealth of data from the Gateway box.


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