Why I Didn’t Want A Tesla Battery
I recently posted about my experiences of getting quotes for Solar Power (Obtaining Quotes) and one of the questions I have been asked is “Are you getting a Tesla Battery?”
Here are my reasons why not
The total installed cost of a Powerwall 2 battery is being quoted at $10,150.
With 13.5 kilowatt-hours of storage that means a cost of approximately $750 per kw hour that’s quite an effective price.
My solar system is limited by suitable roof space to just over 3.00kw
The estimated power generation is around 4000kw hours a year with a monthly average in summer of 16kw hours a day.
In winter it is much lower at an average of 6 kw hours per day.
Prior to the solar installation we were using about 7- 8 kw hours/day without using air conditioning. and another 4-5 kw hours with air conditioning.
It would probably be more if we were home all the time but we both have part time jobs.
In Summer we have a lot of excess solar power, but we are only using 2 – 4 kw hours of grid power when the panels aren’t generating so the battery will only save us around 2 -3 kw hours per night.
In winter we won’t have much excess power during the day so I would estimate that we will only be able to put 1 – 2 kw Hours per day into the battery which will get used up every night..
Overall it looks like we would probably average 2kw hours, or less, of power from the battery a day.
With our supplier, Powershop, the benefit of using power from a battery is approximately $0.25 /kw hour (The difference between the ‘Feed in rate’ and the ‘Anytime rate’)
Our saving = Days in the year x Average kw hours saved x Benefit from battery use
= 365 x 2 x $0.25
= $183 per annum (a rate of return of less than 2% on the $10,000 investment)
This is a much worse rate than overall solar installation . . . see Reviewing Solar
With battery life guaranteed for 10 years you won’t be seeing any real savings, not even if the battery lasts a further 5 years.
If Tesla, or someone else, were to offer a battery system with a quarter of the capacity(say 3kw hours) for a quarter of the price ($2500) I might get excited.
If you have got a lot more panels and a high evening, and night time use, then a Tesla Battery may work for you.