How Long to Break Even With a Tesla Powerwall Battery by Charging During Off Peak Hours?

The thought experiment:

Is it possible to save money eventually by charging the power wall during off peak hours and power your house with the power walls during on peak or higher rate times of day. How long will it take to recoup the costs before you start saving money?

Current 2018 Duke Energy Wake County, North Carolina Rates

Type of Rate On Peak Shoulder Off Peak
Normal/Flat 23.955¢ per on-peak kWh 12.444¢ per shoulder kWh 7.511¢ per off-peak kWh
Time Of Use (TOU) 10.868¢ per kWh 10.868¢ per kWh 10.868¢ per kWh

Lets Do the Math!

According Tesla’s website for powerwall, the cost of the power wall for 30 kWh per day (average) requires two power walls @ $14,500 (not counting installation)

My worst month or highest energy usage was in August which was around 2200 kWh.

Scenario Monthly Bill@ 2200 kWh Monthly Savings@ 2200 kWh Break Even Time
Normal $239.10 $0 Impossible
PowerWall off Peak rate $165.24 $73.86 197 Months or 16.5 years

So “Best case” scenario every month is your worst or most power used month of 2200 kWh, it would take about 16.5 years to start making money or breaking even. This is for North Carolina and maybe other states have a better Time of Use program. If you are in North Carolina, you might want to think of another strategy.

About Daniel Fredrick

Technology enthusiast, Programmer, Network Engineer CCIE# 17094

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