Is A Powerwall Worth It?

Primarily for economic reasons, I covered our roof with 10kW of solar panels. As a producer of electricity, it no longer made sense to pay a utility company for natural gas so the furnace was replaced with heat pumps and the water heater was replaced with a HPWH. The fireplace and chimney were anachronisms I was happy to get rid of. I removed all the gas lines and had PSE remove the leaky gas meter as well. From a safety perspective, ridding our home of combustion appliances was a big win.

While on the topic of safety, the Big One is coming. Our home was built in 1955, way before the Nisqually Quake and updated building codes. I’ve done a few seismic retrofits as suggested by the City. The most important thing, literally, is surviving the quake, so making sure our house doesn’t collapse is a good start. The next most important thing is potable drinking water. I warehouse a weeks worth. For lighting we have camping headlamps, Mr. Beam night lights around the house (with rechargeable AA batteries that last about a month) and outside, I’ve got solar LED lights attached to the house. They’re really nice when walking around the house at night and would suffice during a power outage.

What I don’t have is energy storage. For the safety of linemen, when the grid is down, so is my array. I want a Tesla Powerwall so I can operate off grid. For $6k, Tesla provides a 14kW battery and the transfer switch that enables off grid operation. In the summer, our array produces double what we use (including EV charging) so a single Powerwall could easily power our house, plus extension cords to the neighbors for their fridges, indefinitely. In mid-winter, with no visible sun and freezing temps we could drain a Powerwall in just two days. But after a winter disaster, we could turn the heat off, dress warm, and power the house for weeks. Or heat just one room. That’s a compelling use case, but I have yet to conclude that the potential losses from not having a battery (spoiled food, no lights, no cooking, no heat) during an outage outweigh the $6,200 price tag.

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