"Is it too hot to leave them outside?"

A homeowner looking to add backup power asked a simple question online: should the batteries be installed in the garage or on an outside wall that receives strong afternoon sun?

What people had to say

The question appeared in a Reddit thread on the r/TeslaSolar forum and focused on a setup with two Powerwall 3 units, an expansion pack, and 18 kilowatt-hours of storage.

The homeowner's main concern was straightforward: "Is it too hot to have them outside?" Commenters quickly jumped in with advice and opinions.

One user pointed out that the Powerwall 3 is rated for "-20 to +50 C (-4 to 122 F) including direct sunlight." That commenter also said that "At the extremes, the battery self limits to preserve lifespan."

Others said the published temperature range does not fully answer the placement issue. Some noted that indoor installation can reduce temperature swings, while outdoor placement may help avoid garage space problems and may better fit certain safety requirements.

Rules for garage installations varied widely in the discussion. One commenter said, "My local fire department requires both a heat detector AND sprinkler system to be installed in the garage if I want a battery," and added that their city also required a bollard, distance from the entrance, and a "solid core self-closing door."

Another homeowner said their installation contract specified that an outdoor battery "will need to be installed on a north-facing wall, or a wall that is shaded," unless it is placed inside a cabinet.

Structural support was another concern. One commenter estimated that two Powerwall 3 units plus one expansion pack would weigh "about 850 lbs," making wall suitability another factor to check.

When outdoor placement was allowed, commenters kept returning to shade as a key priority. One said that "any basic shade system like an awning or umbrella or whatever solves most of the temperature issue," while another argued that batteries "will be happier over time in cooler shady location" if they must be installed outside.

Altogether, the discussion became a practical checklist covering wall orientation, required clearances, mounting height, conduit distance, and whether garage placement satisfies local code.

What can be done?

No matter where the homeowner places the battery backup, storage can help protect a house during outages, lower energy costs, and increase energy independence.

For homeowners comparing systems and installation details, EnergySage is one place to review home battery storage options and compare installation estimates. EnergySage has teamed up with electrification brand Qmerit to help homeowners find pricing on home battery storage solutions.

For buyers who do not need a whole-home system, Pila offers another backup option. Its plug-and-play batteries cost a fraction of a full backup setup and can keep essential appliances like refrigerators running.

Where can I learn more?

For more on Powerwall ownership and installation, these stories look at Tesla's home battery technology, competing backup options, installation growth, and how some owners are using Powerwalls.

• Tesla's new home battery system shows how backup power can energize a house.

• Electricians weighing alternatives to Tesla's battery say newer backup options are winning over homeowners.

• Tesla has passed half a million installations worldwide as Powerwall adoption keeps climbing.