Tesla Powerwalls

[maknilsin]

Tesla Powerwall (And Solar) Saved An Aussie Household 92.2% On Their Electricity Bill

What are everyone's thoughts on the Tesla Powerwall? Looks like people are really starting to see the cost benefits of these units and it looks like the ROI isn't anywhere near the originally predicted 20 years.

I would definetely enjoy my power bill only be $178 a year! 

[BIM_Engineer]

"Sometimes the cutting edge is also the bleeding edge"
Further time based simulations & Proofs required

[Jason]

Good topic @maknilsin.

I am also keen to read what other Workshop members think about investing in this technology.

One consideration that I've not seen many people make is the opportunity cost of the initial investment in solar and the batteries. That is, what you would save if you put that money into reducing your mortgage. 

You might also find this Workshop discussion of interest - Reducing your power bill

Jason

[Isobel]

I was very excited when I first saw the Tesla Powerwall. I want to install solar panels on the roof and get some batteries that can store the electricity we would generate. I reckon that one day it will be feasible to go off the grid altogether. I really hope these battery systems become widely available and affordable soon. 

[Brad]

Interesting point @Jason given the article gives a 6 year payback time frame.

Borrowing an engineer's numbers -

80% drain on battery gives 10 year service life so 40% ROI, he does claim the payback is 10 years i.e. 0% ROI.
100% drain is 2 year service life so -80% ROI. Explains why power tools now have a 20% reserve on batteries.

The solar hot water at home lasted 25 years so got to be happy with that.
Solar power took the sweet spot deal that took the bill down 25% with 7 year payback, still on a good buyback rate.

There is a trial in Adelaide where you could have a Tesla system for $2000 installed if they could buy back power when needed. Saved them from upgrading the grid in a new housing development and a no brainer if you had the money at the time.

If you pay full price and believe in the 10 year service life then paying off your mortgage makes sense, if you can get extra years out of the Tesla that is getting a better return. In the real world who does pay down debt instead of spending time in Bali?

[Brad]

@Isobel if you know what your energy usage is you can calculate how many panels you need to go off grid and check if you have the space to put the panels up.

In my case the answer is I run out of roof space, also makes battery storage a moot point for the house.

Tesla not being an option for me and I want to do some small scale things like a garden shed for the outdoor tools I can use Gel Deep Cycle Batteries, not as trendy but you can scale it to your needs.

You can start calculating at a US site.

https://www.wholesalesolar.com/solar-information/start-here/offgrid-calculator

[Jason]

@Brad We also installed a solar hot water system about a decade ago and it certainly paid for itself. 

I guess the main problem with any of the calculations is that you don't know what the price of electricity is going to be in the future. The only guarantee is that it will be more expensive! 

Another consideration: I noticed a television advertisement last night for a new home that explicitly called out the addition of solar panels and a Tesla Powerwall. I imagine it will be a very attractive inclusion to those looking to buy a home that could help re-sale. 

Jason

[Isobel]

Timely article, but short on actual data - https://www.domain.com.au/news/is-it-really-worth-getting-solar-panels-to-reduce-the-cost-of-future-...

[darylhewston]

Too much conflicting data floating around. The saving of 92.2% is not just because of the powerwall. The family in this article also replaced standard lamps to LED, changed the pool pumps etc. A proper study/review needs to be done. I do like the idea that you will have power available during blackouts if you have battery storage.

I am a firm believer that all new homes in Australia should have a minimum of solar hot water, solar panels, rainwater tank and grey water system.

[Brad]

@darylhewston 

---

. I do like the idea that you will have power available during blackouts if you have battery storage.

---

You also need an isolator switch so power can't go to the grid and the grid shut your power down, just a little something they forget to mention in the race for low price advertising.

Facts on battery life seem to be missing leaving educated guesses based on similar batteries with 100 and 80% drain.

Some light reading...

https://www.solarquotes.com.au/blog/powerwall-alternatives/

Comments may do your head in.