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A home battery announced this week holds 39.2 kWh, nearly three times what a Tesla Powerwall 3 stores, and enough to run an average house for a day and a half on its own. Base Power's new Base Core launched alongside a $1 billion funding round that values the three-year-old company at $13 billion. If you've been shopping for home battery storage using last year's numbers as your baseline, it's worth pausing. The baseline just moved.
Key takeaways
- The new size ceiling is roughly 40 kWh, not 13.5 kWh. Base Power's Base Core stores 39.2 kWh per unit (78.4 kWh for two), next to 13.5 kWh for a Tesla Powerwall 3 and 13.6 kWh for a FranklinWH aPower2.
- The money says investors think batteries are grid infrastructure now, not backup appliances. This is Base Power's third major raise since 2023, and it values the company at $13 billion.
- "Bigger" doesn't mean "buy bigger." Base Power's giant batteries come through a lease-and-subscription model, not a purchase. Size and ownership are two separate decisions, and mixing them up is how people end up in a contract they didn't mean to sign.
- Your sizing math hasn't changed. A bigger battery on the market doesn't mean your house needs one. It means the ceiling on what's available moved, which only matters if you were already bumping into it.
What Base Power Actually Announced
Base Power, an Austin-based home battery company founded in 2023, announced on August 3 that it raised $1 billion in Series D funding at a $13 billion post-money valuation, bringing its total capital raised to more than $2.5 billion. The round breaks down like this:
- Led by: Ribbit, Addition, Valor Equity Partners, and JPMorganChase's Strategic Investment Group
- Also participating: Altimeter, D1 Capital Partners, Sands Capital, Coatue, Layer Global, and Energy Impact Partners
- Returning investors putting in more money: Thrive Capital, a16z, Lightspeed, Trust Ventures, and CapitalG
Base Power says the unit installs in under an hour and is built to keep working through extreme heat and cold.
Alongside the funding, the company launched Base Core, built at its own Base Factory 1 in Austin, where it says it's now turning out thousands of units a month. A single Base Core stores 39.2 kWh; two paired together hold 78.4 kWh.
CEO and co-founder Zach Dell pitched it on installation speed and grid resilience. COO and co-founder Justin Lopas tied the Austin factory to bringing storage manufacturing back to the US instead of importing it.
Base's batteries are currently deployed in Texas and Illinois, with a combined fleet over 500 MWh, and the company has grid-services deals with utilities including El Paso Electric, Austin Energy, and CoServ covering more than 200 MW of capacity. Valor Equity Partners' Antonio Gracias, whose firm led the round, called Base the fastest, most cost-effective way to add grid capacity right now. That line is worth sitting with, because it tells you who this battery is actually built for.
How Big is 39.2 kWh, Really?
Top Tesla Powerwall Alternatives in 2026: Price & Specs ComparedNumbers on a spec sheet are easy to skim past. Here's what 39.2 kWh looks like next to the batteries that have defined the residential market for the last few years.
A single Base Core holds roughly three Powerwall 3s' worth of energy in one box. That's a real jump, not a marketing rounding error. It's the first time a mainstream residential product has landed in territory that used to take stacking three or four separate units to reach — and it's worth noting that route already exists, just piecemeal: Enphase's IQ Battery 5P is sold as a 5 kWh module precisely so homeowners can add capacity in stages instead of committing to one giant box on day one.
The Fine Print: You're not Buying This Battery
Here's the part that matters more than the kWh figure. Base Power doesn't sell the Base Core. It owns it, installs it on your property, and leases you the backup power. Based on how the company has publicly described its program, homeowners pay a modest upfront installation fee and a monthly service charge, then commit to buying electricity from Base Power at a fixed per-kWh rate for a multi-year term. Base's software charges the battery when grid power is cheap and discharges it, sometimes back to the grid, when demand and prices spike. Homeowners get a cut of that arbitrage profit.
A network of home batteries that a company coordinates like a single power plant, charging and discharging thousands of units in sync to help balance the grid. Participating homeowners get paid for the privilege. Base Power's entire business is built around this model instead of one-off equipment sales.
Our read: this looks a lot more like a rooftop-solar power purchase agreement than a straight purchase of a stackable system like an EG4 battery. You get backup power and a smaller upfront bill. Base Power gets a fleet of dispatchable batteries it can sell grid services from, plus your electricity spend locked in for years. Neither of those is a bad deal on its face, but they're different deals, and the size of the battery box shouldn't be what decides which one you sign.
Does Bigger Mean Better for Your House?
Almost certainly not, at least not automatically. The 39.2 kWh number is impressive because it's new, not because your home needs it. Most single-family homes running essential circuits during an outage (refrigerator, some lighting, a well pump, part of the HVAC) get through comfortably on 10 to 15 kWh of usable storage. That's exactly why Powerwall 3 and aPower2 landed where they did. Homes that genuinely need something closer to Base Core's range tend to have a specific reason: whole-house backup that includes central AC, heavy daytime EV charging, or medical equipment that can't tolerate any gap in coverage.
How many batteries does it take to power a house?Practical advice: before a bigger number pulls you toward a bigger battery, pull your utility bill and work out your actual average daily kWh use. Then decide how many hours or days of backup you actually want, not the maximum available, but the maximum you'd realistically use.
Buy vs. Subscribe: Two Different Storage Decisions
Neither column beats the other on its own. They fit different budgets and different appetites for a multi-year commitment tied to one company's rate structure.
What to Do Before You Decide
- Verify your actual outage-hour or outage-day target before comparing battery sizes. Most sizing mistakes happen here, not at the spec-sheet stage.
- Ask any installer quoting a bigger system whether you're buying the hardware or leasing capacity, and get the total multi-year cost in writing either way.
- Flag any quote that bundles a fixed-rate electricity contract with the battery, and read the rate-escalation and early-termination terms before signing.
- Pause on chasing the largest available kWh number if your outage needs are modest. A right-sized purchase usually beats an oversized subscription.
Base Power just showed the industry you can triple a home battery's capacity without adding a minute to the install time. Whether that's good news for you comes down to one question the marketing won't answer for you: are you buying a battery, or signing a multi-year contract that happens to come with one attached?
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Alina has always been drawn to the intersection of technology and everyday life. Joining A1 SolarStore as a contributing writer, she brings fresh curiosity and a researcher's eye to the topics of clean energy and sustainability.
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