I'm having solar and the powerwall installed in a couple of weeks and my intention is to have it installed outside. This is what we planned for and I think it will be the best overall location for me. East facing wall and right next to my meter. They told me being outside has no net effect on the powerwall.
I was curious what others thought about mounting it inside (say an unheated garage) vs outside in the sun.
- In Pleasant Hill, the summer months in the sun will be too hot for it, and it will degrade quicker.
- In California, night times can be cold, causing dendrites to grow more and require more heating to keep it warm enough, and it might degrade quicker and will use more energy to heat it.
- It takes more space inside if you put it inside. You need ventilation clearance and the ability to easily access it by workmen where ever you put it. You need to keep it free of dust and other dirt in the environment. So, no tucking it behind stuff, no storing stuff around it, no working with dusty tools near it, etc.
- Outside it is subject to more vandalism.
- Tesla used to prefer it outside, but since decided to prefer it inside. I think this is because it gets less damage by bad weather from outside. Also, they finally realized vandalism wasn't an irrational fear once they heard of it happening.
- Where ever it is, in an extreme physical accident, it can cause a pretty severe fire. I see that being more of a problem from vandals outside than when inside, but either way, any physical accident enough to break the box could trigger it. They are pretty strong boxes, so this must be something super extreme.
In balance, I have always preferred inside for the above reasons, but now that we know from experience that my reasons are even more true, and that now Tesla has shifted from preferring outside to preferring inside, that puts way way more weight behind my original preference, and now I strongly recommend inside. Having said that, mine are outside, and I regret it, but there is plenty of space outside and no way to currently find enough space inside without starting World War Five. If I ever get to own this property, then I will build a fully and well insulated shed around them in-place (or raise them up to place insulation underneath and behind first), and turn them into inside units complete with perfect Lithium-Ion temperature heating and air conditioning.
The ideal space would be a purpose-built insulated and temperature controlled and properly dehumidified (not much humidity, but the minimums should be met) utility shed close to the house far from bedrooms. Another word for that for most US homes is the garage, but keep in mind, in many climates, the garage would not qualify exactly for what I said without work. For similar reasons to PowerWalls, I've long been a loud advocate for turning garages into insulated thermally conditioned rooms just like the rest of the home (but with separate air to air out car greases), since Lithium Ion battery cars put out way less pollution AND want to be in a much tighter temperature range for maximum longevity and use (bad dendrites form in low temperatures, and battery gets bad in high temperatures too, and optimum charging temperature is somewhere around room temperature -- I haven't memorized the correct number). That also allows your car to avoid having to self-climatize every time you want to use it when you go to use it. That means insulating the garage in a way you never have, and that means learning things about floors like you can't drive on unsecured floors (unsecured plywood would fly out from under cars like missiles and decapitate your family -- I learned this the hard way when I raised a truck up with plywood, and luckily the only thing hurt was the truck and some garage doors -- and it was the first time I tried it, so I doubt any type of freak accident -- that flooring has to be solidly part of the ground to be used for vehicles), yet you would need to insulate the floor, all cracks, windows, doors, walls, and roof, and at the same time take the weight of a multi-ton vehicle without hurting anyone. Fun construction to be sure.
This really should be kept in mind when building a new home every single time. Huge utility sheds (one for power and one for communication, and obviously both quite large), well insulated, well thermally controlled, and the same for garages that are 100% electric vehicles, with good ventilation, since those cars still have greases and other fumes, but a tiny fraction of ICE cars. Since most homes were designed wrong for the modern age we live in of home batteries and battery cars, that means we thus need to be smart about how we build upgrades to existing structures to handle current uses (and future uses too).
A nice option for decent land sizes with existing structures on them I did hint at above: put in a nice shed. But that could quickly add up to mass frustration as you realize how expensive that option is, and how insufficient your shed size is once you add in your second solar array, your third battery pack, and the two dozen panels you have to build and the network of large conduit required to support all that and all the 3' servicing requirements and ventilation required. I want to say you better be building a green house for your wife twice as large, but that could be like buying cooking dishes for a birthday: a message to slave in the garden. You better find out what the gift is that offsets all the space taken by yet another machinery room (in addition to the garage, HVAC, water heater, air conditioner, computer, office, television, kitchen, laundry room, garden tools, workshop, and every other machine room you already messed up your property with in the opinion of your spouse who doesn't quite think those things are so lovely or fun).