Tesla Powerwall owners taking part in South Australiaâ€™s Virtual Power Plant (VPP) project have a continuing exciting ride for a few more days yet.
With the Victoria-South Australia interconnector out of action following storm damage, their batteries will probably see ongoing heavy charge/discharge cycling as the VPP plays its role in keeping South Australiaâ€™s grid stable.
As South Australiaâ€™s InDaily reported, storms in late January damaged transmission towers near the Heywood interconnector, and on February 3 it was stated repairs could take up to two weeks. At the time of publishing, itâ€™s estimated the fix will be complete on February 14.
A VPP participant contacted SolarQuotes early on in the event to tell us he noticed a big upswing in the number of charge/discharge cycles his battery was experiencing.
He told us his battery was being:
â€ścycled every day unnecessarilyâ€ťÂ (from his point of view),
and he is concerned this could be adding to his power bill, because itâ€™s happening:
â€śeven out of solar hoursâ€ť
(hence his concern about costs).
He said Tesla had advised him that:
â€śanyone who is part the Tesla VPP plan will have their system used or abused in a similar mannerâ€ť.
Our informant received the following explanation in an e-mail from Tesla:
â€śYour battery was charging and discharging in order to support the SA grid during what might have otherwise been an outage across the network. This is normal aggregation behavior and shouldnâ€™t be considered unnecessary â€“ itâ€™s necessary as part of the virtual power plant operation.Â Any grid charging the Powerwall experiences as part of the optimization in the VPP will be a credit line item on your power bill (meaning, this is not an additional expense or kW you will pay for).â€ť
â€śThe warranty guarantees 70% energy capacity at the end of 10 years. The activity youâ€™re seeing is still covered by this warranty.â€ť
SolarQuotes asked Tesla Australia to comment, but we havenâ€™t yet had a response.
Our friendâ€™s concern is reasonable, but weâ€™d hope customers on the VPP wonâ€™t be hung out to dry.
As weÂ commented in 2016 when the Powerwall 2 was released, the companyâ€™sÂ â€śunlimited cyclesâ€ť warranty (PDF) is not quite unlimited, but itâ€™s pretty darn good. The warranty is only â€śunlimitedâ€ť if the installation is only used to provide either daily usage or backup power for the customer.
Use in a VPP is obviously outside that spec, so the warranty is more limited (but still good), and we worked out that the â€ś37,800 kWh deliveredâ€ť warranty is 3,200 cycles â€“ about eight yearsâ€™ worth if cycled once a day.
Whatâ€™s happening in South Australia at the moment could add up to be more than a â€śdaily cycleâ€ť, so itâ€™s fair for owners to be concerned. As our informant noted, this could well be the prevailing condition for users for the whole of the interconnector repair.
â€śExpect continualÂ aggressive battery power cyclingÂ if you are a VPP participant for the next two weeks,â€ť he wrote.
â€śPower generation, particularly solar generated power will have nowhere toÂ go, so the batteries will be sharing that power around.â€ť
Teslaâ€™s silence isnâ€™t surprising â€“ the company loves being completely in control of its media narrative1 â€“ but itâ€™s odd that with what looks like a good news story in the offing, itâ€™s got nothing to say. At the cost of extra battery cycling (and the company promises customers will still get their warranted 70% capacity at the end of 10 years), the VPP is working as expected. Itâ€™s contributing to grid stability in the face of challenging conditions.
It would be interesting, for example, to chat to an engineer about what the challenge looks like from the VPP operations room â€“ what are they learning about power flows between batteries? Is there anything to learn from what is, in practice, an experiment in accelerated aging? Weâ€™d love to hear from you, Tesla.