One Tactical Unlock at a Time: How Tesla Built Powerwall

Cole Ashman

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One Tactical Unlock at a Time: How Tesla Built Powerwall<br>Approaching vertical integration as a rapid series of strategic steps was the secret sauce to market dominance for Tesla Energy

Cole Ashman<br>Jul 14, 2026

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Co-Authored by Cole Ashman (Founder/CEO, Pila) & Chad Conway (Founding Partner, 981.vc)

The unsexy Resi battery walked so the Powerwall that we know and love could run.<br>Two-and-a-half repurposed Model S battery modules… a Schneider inverter designed for 48V lead acid racks… a white sheet metal box with no branding, no app. This is the product that kickstarted Tesla’s residential energy business – it’s an epic and little-known hero origin story.<br>Powerwall 2 and 3 are the products most call to mind when they think of Tesla’s mastery of vertical integration in home energy products. The high-capacity battery design, the impressive hybrid inverter, the super-smart site controller, solar optimization, islanding devices – all in one box, one platform, all Tesla. It’s become an oft-cited template: control everything, own everything, and you win.<br>The thing is, that was the destination , but it wasn’t the path . I’ve often wondered if confusing the two has led early-stage hardware companies in the wrong direction.<br>First, where we’re coming from: I (Cole) joined Tesla in 2017, working on new product development globally for Powerwall. Chad joined Tesla even earlier in 2013 and became the 5th employee on the brand-new Energy team, and went on to lead Applications Engineering across the Powerwall ecosystem. We both later helped build the Product team at SPAN. In 2024 I founded another battery company, Pila, to expand access to smart home batteries.<br>I hope telling this Tesla story from the inside perspective proves helpful for those looking to build ambitious hardware platforms.

Hello from a couple of energy product nerds

The Premise

Why not build the whole damn thing integrated from day one – pack, power electronics, and compute under one roof, on a fully automated line – and win on the entire cost stack?

It’s a question I’ve often encountered in talking about system costs, with investors and with other founders. The honest answer is: those usually aren’t the right problems to be focused on at the earliest stages. They may be in a few years in – But trying to solve them in year 1 or 2 will slow you down exactly when you need to move fastest.<br>Chad has a refrain he uses with every hardware founder he backs at 981: “As soon as you take venture capital, you have a 10-year window and you need as many shots on goal as possible. The founders who move fastest are the ones who resist the temptation to build everything and stay ruthlessly focused on what creates the next unlock.”<br>The Tesla vertical integration story is compelling because it’s true… eventually . But it often gets told backwards. Held up as a masterplan rather than the result of fast, serial, focused bets.

Where It Started • The Resi Battery

It all started with grant funding from California.<br>In 2012, Tesla’s fledgling residential energy group secured a CEC grant with a specific goal: prove that a high-capacity lithium-ion battery pack could be safely and effectively connected to a home for backup power. Nobody had done this at residential scale. The team was tiny – a handful of mechanical and firmware engineers working inside an EV company still fighting to survive.<br>The product they built was as minimal as it could be: two-and-a-half modified Model S battery modules with a basic BMS, packaged in a simple white enclosure and wired to an off-the-shelf Schneider XW 4048 (an inverter designed for 48V lead-acid battery arrays). One piece of real ingenuity was a small site controller : a basic edge computer that pulled in battery telemetry and could adjust the Schneider’s voltage setpoints – effectively coaxing a lead-acid inverter into following a Li-ion charge curve. The battery was supposed to just react to the inverter, but in this case it was steering it. Otherwise, Tesla built around the inverter’s spec, since that meant moving faster.<br>“We picked the inverter and made the battery work with it,” Chad recalls. “No new tooling, as few custom parts as possible. Just get something out there.”<br>Tesla deployed ~400 Resi units in California. It proved the concept, and seeded what would become one of Tesla’s most important product lines.

Powerwall 1 • The First Big Unlock

The home battery market was picking up. Germany had been the first mover on residential solar, and its storage market had started to take off around 2015. Competitors were emerging across Europe. The Tesla team knew the next product had to be meaningfully better – cheaper, denser, and differentiated enough to launch a brand.<br>Hello, Powerwall 1. Two stock Model S modules – same form factor, same production line, different cells – and a custom DC-to-DC converter (DCDC) wrapped inside a...