When we started designing Kora’s battery storage architecture, we kept returning to the same fundamental tension: homeowners have predictable current needs but unpredictable future needs. An EV might be two years away. A second EV might follow. Solar panels might get added. A home office might create new backup requirements. How do you sell someone a storage system today that serves them well in 2031?

Our answer was modularity. Not as an afterthought, but as the central design principle.

The Problem With Fixed-Capacity Systems

Most home battery systems on the market are designed as fixed-capacity units. You buy 10 kWh, 13.5 kWh, or 20 kWh. If you want more capacity later, you purchase an additional unit — but those units are typically designed to operate in parallel as identical siblings, not as part of a coherent system that treats all capacity as a unified resource.

There are several problems with this approach. First, it forces customers to forecast their future needs accurately at the time of purchase — or pay a premium for capacity they won’t use immediately. Second, additional units added later may not integrate seamlessly with the original installation. Third, the system management layer often treats parallel units as separate entities rather than optimizing the entire storage pool holistically.

We wanted to build something different: a system where adding capacity was as natural as plugging in a new device, where the management layer always had a complete view of all storage, and where the economics of the initial purchase weren’t distorted by uncertain future needs.

The Powerblock Architecture

Each Powerblock unit provides 16 kWh of usable lithium iron phosphate (LFP) storage capacity. Units connect to the Kora Smart Panel via a standardized high-speed bus that carries both power and data. From the Smart Panel’s perspective, adding a Powerblock is plug-and-play — the system automatically detects the new unit, incorporates its capacity into the optimization model, and begins managing it as part of the unified storage pool.

The maximum configuration supports 7 Powerblock units for a total of 112 kWh — enough to power an average American home for approximately 4–5 days without any grid or solar input. For households with solar, 112 kWh of storage can provide indefinite backup capability in most U.S. climates.

Units can be added over time without disrupting the existing installation. Each unit mounts independently to the wall and connects to the main power bus. Installation of an additional unit typically takes 30–45 minutes — no panel replacement, no rewiring of existing units, no re-commissioning required.

Why LFP for Residential Use

Lithium iron phosphate chemistry is a deliberate choice with specific advantages for residential applications. Compared to the nickel-manganese-cobalt (NMC) chemistry used in many EV batteries and some earlier home storage products:

  • Cycle life: LFP provides 4,000–6,000 charge cycles vs. 1,500–2,500 for NMC — effectively 2–3x the usable lifetime
  • Thermal stability: LFP is significantly more stable at high temperatures, reducing fire risk in garage installations that may reach 100°F+ in summer
  • Depth of discharge: LFP can be routinely discharged to 80–95% depth without significant calendar degradation
  • Supply chain: LFP contains no cobalt, reducing supply chain risk and ethical concerns around cobalt mining

The tradeoff is lower energy density — an LFP battery is physically larger than an NMC battery with the same capacity. For residential wall-mounted storage, this is a minor concern. The improved safety and longevity profile makes LFP the right choice for a product that will sit in a residential garage for 15+ years.

Degradation: What the 10-Year Warranty Actually Covers

Every Kora Powerblock comes with a 10-year, 80% capacity warranty. If any unit degrades below 80% of its original capacity within 10 years of installation, we replace it at no charge. This warranty is based on our characterization of LFP degradation curves and our confidence in the chemistry.

In practice, our testing shows that Powerblocks operated within their design parameters retain 88–92% capacity after 4,000 cycles — roughly 11 years of daily cycling. The warranty floor of 80% represents a conservative threshold well below our expected performance curve.

Understanding what affects degradation helps you maximize your system’s life. The main factors are operating temperature (higher temperatures accelerate degradation — keep your Powerblocks in a conditioned space where possible), depth of discharge (shallower cycles extend life — the AI reserves 10% buffer by default), and charge rate (faster charging at high temperatures causes more stress than slower charging). The Kora AI manages all of these automatically to optimize lifetime performance.

The Right Size to Start

One of the most common questions we get from prospective customers is: how much storage do I actually need? The answer depends on what you’re trying to accomplish.

TOU arbitrage only: 16 kWh is typically sufficient. A single Powerblock can capture the peak–off-peak spread for most average households and pay for itself through TOU savings alone.

Whole-home backup (1–2 days): 32 kWh is the sweet spot for most households. Two Powerblocks provide enough storage to run an average American home through a 24–48 hour outage while maintaining comfortable reserves.

Extended backup with solar: 48–64 kWh maximizes the solar storage buffer for households with significant rooftop generation. Combined with 8–12 kW of solar, this configuration can provide indefinite backup in sunbelt states.

EV-heavy households: Add 16 kWh per EV you plan to charge primarily from stored energy. An EV driving the U.S. average of 37 miles/day consumes roughly 12 kWh — a single Powerblock provides about 1.3 days of average EV charging on top of other home needs.

The Expansion Path

What we hear most from customers who started with 16 kWh is that they wish they’d started with 32. The utility of storage compounds: once you have it, you find ways to use it. Charging your EV overnight from stored power. Pre-conditioning the house before peak hours. Reducing grid dependence during planned outages. The value of additional capacity becomes apparent quickly.

Knowing that expansion is simple and affordable changes the calculus on the initial purchase. You’re not committing to your maximum configuration on day one — you’re starting with what makes sense today and growing as your needs evolve. That’s how we think the residential energy storage market should work.