In early May, Tesla Motors unveiled the new Powerwall, a home battery pack to be used in conjunction with a solar panel system to provide power for the home when the sun's not shining. The Powerwall is being touted as a solution to the mismatched energy supply from solar PV systems. Currently, the Powerwall battery price is unmatched in the residential market, including the best lead acid batteries. Lithium batteries are ideal for solar because it does not need a full recharge.
So how affordable is the Powerwall really, and is it a viable option for homeowners looking to reduce their dependence on the grid, or get off it entirely? The Powerwall is available to installers in both a 10 kWh and 7 kWh model at $3,500 and $3,000 respectively (price excludes inverter and installation), with the 7 kWh intended for daily use and the 10 kWh intended for backup use only. Up to 10 Powerwall battery packs can be linked together.
The average California home will need 7-9 Powerwall battery packs to power itself for an entire day. At night when your solar panels are not producing energy, you’re paying roughly three times as much per kWh to get electricity from the powerwall when you could simply get your electricity from the grid at roughly 10 cents per kWh. It is significantly cheaper to purchase a gas generator and run it when the power is out (gas included). The truth is, blackouts rarely happen. With the Powerwall you’re paying for the luxury of having power for your home for a few hours following a blackout.
The residential battery market is expected to grow significantly in the near future, with serious competitors to the Powerwall expected to enter the market in 2-4 years. It is safe to assume the price of energy storage will continue to decline over the next few years at which point it may be economical to add an energy storage system to your existing solar system.
If you are a homeowner who wants the ability to go completely off-grid, and are not particularly concerned about the economics behind that, the Powerwall is an option.
The Powerwall has us at Pick My Solar excited because it represents the beginning of a residential energy storage system market that will make clean distributed energy even more viable than it already is.