The Tesla Powerwall

Evelyn Xue
December 15, 2015

Submitted as coursework for PH240, Stanford University, Fall 2015


Fig. 1: Tesla Powerwall. (Source: Wikimedia Commons)

The Tesla Powerwall Battery presents a unique opportunity to leverage battery and power grid technology to live a more energy efficient life. The availability and access to this new technology can mean important changes to the way people use power, especially in the residential sector. [1] The Powerwall is a particularly viable and appealing product to many consumers due to the amount of money they might be able to save on their overall electric bill, meaning shorter payback times for the purchase of the battery itself. [2]


The Powerwall battery is very popular because it is cheaper than many of its competitor's products, and does not require much maintenance or monitoring. It is essentially a lithium ion battery pack and uses liquid thermal controls. The cost is about $3000 (USD) for the 7kWh daily cycle for the daily cycle batter, and has a 5 kW continuous power output and a 7 kW peak power output. [2] Though the battery includes a DC to DC converter, it does not include a AC/DC inverter, so it may incur extra costs during installation. [2] The battery comes with a 10 year warranty and operates at around 92% efficiency and weights about 100 kg. [2] The cost of the battery has reached a consumer friendly price due to improvement in battery technology. [3] In addition, there has also been a decrease in the cost of the PV cells found in solar panel (this generates energy that gets stored in the battery) due to the downward trending price of Silicon and the creation of more efficient PV cells. [3] The combination of the two have allowed the solar panel and battery system to become viable in everyday households.

Cost Savings and Grid Benefits

Savings for the customer come from the discrepancy between the cost of electric during peak and non-peak hours. Batteries allow the customer to charge the battery during non-peak hours and store the energy to use during peak hours. [3] Therefore, the customer only needs to use electricity during non-peak hours, and thus save money on electricity. In addition, homeowners can also sell the excess power back to the electricity during busy hours. [3]

The usage of the battery could also mean more efficient power grids. The idea is that at times when the regional power grid is reaching a potential brown, battery packs such as the Tesla Powerwall can kick in and allow homes to run off battery for a while to reduce the demand on the power grid. [1] This can also prevent circuits from overloading at critical times, allowing for a reduction of expensive infrastructure repairs and upgrades.

Viable for Everyone?

While the Tesla Powerwall can provide major cost savings in certain households, the same cannot be said for everywhere. The effects are highly dependent on climate conditions and local utility rates. [2] A study was done on storage unit usage in Knoxville and Los Angeles, and it was demonstrated that a battery investment only made sense in certain battery-PV system pairings. [2] The results depended on local utility rates, predicted weather conditions, and size and cost of battery and PV system in the area. [2]

© Evelyn Xue. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] S. Gupta, "From Gadgets to the Smart Grid," Nature 526 S90 (2015).

[2] N. DiOrio, A. Dobos, and S. Janzou, "Economic Analysis Case Studies of Battery Energy Storage with SAM," U.S. National Renewable Energy Laboratory, NREL/TP-6A20-64987, November 2015.

[3] G. E. Mathews, E. H. Mathews, and M. Kleingeld, "Photovoltaic Cells - the Hot New Investment?,"' IEEE 7280279, Proc. 2015 Conf. on Industrial and Commercial Use of Energy (ICUE), 18 Aug 15.