The tech was alluring to those interested in alternative energy, but for many, the starting price of $3,000 was too steep. The battery could only store up to 10 kWh of electricity, or around a third of the amount the average American household consumes a day (the newer version can hold up to 14 kWh).

For some alternative energy enthusiasts, Musk's deal wasn't good enough. Instead of buying Tesla's Powerwall, they build their own DIY versions using recycled batteries for a fraction of the cost. Then, naturally, they share their creations and swap knowledge with other hobbyists across the internet. DIY powerwall enthusiasts congregate on a dedicated forum, in Facebook groups, and on YouTube. They live all over the world: I spoke to makers on three different continents and a half dozen time zones.