EP Cube 2.0 and Tesla’s Powerwall 3 both top out at 11.5 kW of continuous output and handle motor starts rated up to 185 A LRA, according to CSI Solar’s EP Cube 2.0 North America datasheet (V1.6, August 2026) and Tesla’s 2025 Powerwall 3 datasheet. Where they split is how they store energy. Powerwall 3 is a fixed 13.5 kWh unit that grows with 13.5 kWh Expansions. EP Cube 2.0 stacks 5 kWh modules from 5 to 40 kWh in a single unit. This comparison lines up both datasheets and runs worked sizing examples, so you can tell which system fits your home and your installer quotes.
Both systems are sold and installed through certified installers, so this article has no retail links. Specs come from the two datasheets above and from EP Cube’s U.S. product page. Sizing figures are our own calculations, and we haven’t installed or tested either system.
EP Cube vs Tesla Powerwall 3: Spec Comparison
| Spec | EP Cube 2.0 (split-phase) | Tesla Powerwall 3 |
|---|---|---|
| Energy per unit | 5–40 kWh total energy (1–8 × 5 kWh modules) | 13.5 kWh AC nominal |
| Expansion | Up to 3 units in parallel, 120 kWh | Up to 3 Expansions (13.5 kWh each) per Powerwall 3; up to 4 Powerwall 3 units, 7 units total |
| Continuous output | Configurable 5.8, 7.6, 9.6 or 11.5 kW at 240V | Configurable 5.8, 7.6, 10 or 11.5 kW |
| Battery-only output | 3 kW (5 kWh), 7.6 kW (10 kWh), 11.5 kW (15 kWh and up) | Up to 11.5 kW |
| Off-grid boost | Not listed | Up to 15.4 kW off-grid (PV only, −20 to 25°C), with an 80 A breaker |
| Motor starting | 185 A LRA for 1 second | 185 LRA |
| Solar inverter | Hybrid; 6 MPPTs, 60–550V DC, 5 kW max per MPPT; EP Cube’s page lists up to 24 kW PV; AC coupling also supported | Built in; 20 kW DC max solar, 6 MPPTs, 60–550V DC |
| Max charge power | 2.5 kW (5 kWh) up to 10 kW (20 kWh) | 5 kW alone; 8 kW with Expansions |
| Efficiency | Inverter CEC 96.5% | Solar-to-home 97.5% (CEC weighted); solar-to-battery-to-home 89% |
| Chemistry | LFP | LFP |
| Enclosure | NEMA 4X; 30 dB(A) at night, under 60 dB(A) max | NEMA 3R, IP67; under 50 dB(A) typical, under 62 dB(A) max |
| Size / weight | 23.6 in W × 8.7 in D; 36.9–68.5 in tall for 5–20 kWh; 195–479 lb | 43.5 × 24 × 7.6 in; 291.2 lb installed |
| Islanding device | SGNA2-200GX Smart Gateway (200 A) | Gateway 3, Backup Switch or Backup Gateway 2 |
| Connectivity | EP Cube app | Wi-Fi (2.4/5 GHz), Ethernet, cellular; Tesla app |
| Warranty | Over 80% capacity, 10 years or 6,000 cycles | 10 years |
One important difference in the paperwork: EP Cube’s datasheet lists total energy, while Tesla lists 13.5 kWh nominal AC energy. When you compare quotes, ask the EP Cube installer for the usable capacity at your chosen backup reserve.
Key Differences Explained
1. Capacity steps
Powerwall 3 grows in 13.5 kWh blocks: 13.5, 27, 40.5 or 54 kWh per Powerwall 3 with Expansions. EP Cube grows in 5 kWh steps inside one stack: 5, 10, 15, 20 and so on up to 40 kWh. If your target is about 20 kWh, EP Cube can hit it with four modules. With Powerwall 3, your choices are 13.5 or 27 kWh.
2. Power vs size
Powerwall 3 delivers up to 11.5 kW at any configuration. EP Cube’s battery-only output depends on module count. One module gives 3 kW, two give 7.6 kW, and you need three or more (15 kWh) for the full 11.5 kW after dark. With solar running, EP Cube can supply 11.5 kW at any size, per the datasheet.
3. Adding power, not just energy
Powerwall 3 Expansions add energy but no extra power. To go past 11.5 kW, you add another Powerwall 3, up to four. EP Cube scales up to three units in parallel, which EP Cube’s U.S. page puts at 120 kWh and 34.5 kW.
4. Solar design
Both are hybrid systems with six MPPTs and a 60–550V DC input range. Tesla caps solar at 20 kW DC. EP Cube lists 5 kW per MPPT and up to 24 kW of PV on its product page, and also supports AC-coupling existing solar.
5. Physical footprint
Powerwall 3 is one 43.5-inch-tall slab, 7.6 inches deep, at 291 lb installed. EP Cube’s height depends on module count. A 20 kWh stack is 68.5 in tall and 479 lb, and sizes above 20 kWh sit on a long floor base.
Worked Sizing Examples
These examples use illustrative loads. Have your installer confirm with your actual usage data.
| Home profile | Need | EP Cube 2.0 option | Powerwall 3 option |
|---|---|---|---|
| Essentials only: fridge, lights, Wi-Fi, furnace fan | ~0.6 kW average, ~3 kW peak, 12 h overnight ≈ 7.2 kWh | 10 kWh (2 modules, 7.6 kW) | 1 Powerwall 3 (13.5 kWh) |
| Typical home, no AC | ~1.5 kW average, 7 kW peak, 12 h ≈ 18 kWh | 20 kWh (4 modules, 11.5 kW) | Powerwall 3 + 1 Expansion (27 kWh) |
| Summer with central AC | ~3 kW average, 10 kW peak, 12 h ≈ 36 kWh | 40 kWh (8 modules) | Powerwall 3 + 2 Expansions (40.5 kWh) |
| Large home, 2 heat pumps + EV | 15+ kW peak | 2 units in parallel | 2 Powerwall 3 units (23 kW) |
Runtime math. Runtime is usable energy ÷ average load. At a 1.5 kW average, Powerwall 3’s 13.5 kWh gives about 9 hours. An EP Cube 20 kWh stack, if 90% of total energy is usable (an illustrative figure, so confirm with your installer), gives 18 kWh ÷ 1.5 kW ≈ 12 hours.
Motor start check. Both list 185 LRA. Find your AC compressor’s LRA on the outdoor unit’s nameplate. If it reads 90 LRA (example), either system has headroom. Close to or above 185, ask about a soft starter. On EP Cube, remember that battery-only power with fewer than three modules may be the tighter limit at night.
Solar-to-battery efficiency. Tesla lists 89% for solar stored and then used. So 10 kWh of solar shifted into the evening delivers about 8.9 kWh. EP Cube publishes a 96.5% inverter CEC efficiency rather than a round-trip figure, so ask your installer for the round-trip number when you compare.
Comparing Two Quotes Side by Side
Installers quote complete systems, so the sticker totals rarely line up. Here’s a method with made-up round numbers (illustrative only, not real prices) to show how to normalize them:
| Metric | Quote A: EP Cube 2.0, 20 kWh | Quote B: Powerwall 3 + 1 Expansion, 27 kWh |
|---|---|---|
| Quoted total (example) | $20,000 | $25,000 |
| Usable energy | Ask installer; 18 kWh if 90% usable (example) | 27 kWh nominal |
| Cost per usable kWh | $20,000 ÷ 18 ≈ $1,111 | $25,000 ÷ 27 ≈ $926 |
| Continuous kW | 11.5 kW | 11.5 kW |
| Cost per kW | ≈ $1,739 | ≈ $2,174 |
In this example, the lower total turns out to cost more per stored kWh but less per kW. Which metric matters more depends on whether your goal is long runtime or running big loads at once. Run the same two divisions on your real quotes.
Existing Solar vs New Solar
- New solar and battery together. Both systems can take panels as DC straight into their built-in inverters. That skips a separate solar inverter and avoids an extra conversion step when solar charges the battery.
- Existing string or microinverter solar. EP Cube’s datasheet lists AC coupling for existing PV. With Powerwall 3, ask the installer how your existing inverter will connect. Our Powerwall 3 vs Enphase vs FranklinWH guide covers AC-coupled options.
- Planning to add panels later. Check the remaining MPPT capacity. Tesla tops out at 20 kW DC, and EP Cube lists 5 kW per MPPT across six MPPTs.
Which Should You Choose?
| Your priority | Better fit | Why |
|---|---|---|
| Exactly sized capacity in small steps | EP Cube 2.0 | 5 kWh modules, 5–40 kWh per unit |
| Full 11.5 kW from a single small unit | Powerwall 3 | 11.5 kW at 13.5 kWh; EP Cube needs 15 kWh for 11.5 kW battery-only |
| Extra off-grid surge with big solar | Powerwall 3 | 15.4 kW off-grid PV-only option |
| More PV per unit | EP Cube 2.0 | Up to 24 kW PV per EP Cube’s page, vs 20 kW DC |
| Thin wall-mount profile | Powerwall 3 | 7.6 in deep, fixed size |
| Lots of storage in one cabinet | EP Cube 2.0 | Up to 40 kWh in one stack |
| Wide installer network | Powerwall 3 | Tesla and certified installers nationwide |
For deeper dives, read our EP Cube battery review, our Tesla Powerwall 3 review and what a Powerwall 3 costs installed. To compare more brands, see Powerwall 3 vs Enphase vs FranklinWH and home battery warranties compared.
Questions to Ask Your Installer
- What’s the usable kWh at my backup reserve setting, for each quote?
- What continuous output (kW) and breaker size is the system configured for?
- Will it start my central AC or well pump? What’s that unit’s LRA?
- Is my solar DC-connected to the battery inverter, or AC-coupled?
- Which islanding device is included (EP Cube Smart Gateway, or Tesla Gateway 3 or Backup Switch), and is it whole-home or partial backup?
- What’s the price per usable kWh and per kW? Divide each quote so sizes compare fairly.
If you’re planning partial backup, our critical loads panel guide explains how that wiring works.
FAQ
Is EP Cube better than Powerwall 3?
Neither wins for every home. EP Cube 2.0 offers finer capacity steps and more storage in one stack. Powerwall 3 gives its full 11.5 kW from a single 13.5 kWh unit, plus a 15.4 kW off-grid option.
Which one is easier to fit on a garage wall?
Powerwall 3 is a fixed 43.5 × 24 × 7.6 in unit. EP Cube can also hang on a wall up to 20 kWh, but its height grows with each module, and larger stacks are floor-mounted.
Can I add capacity later?
Yes, for both. EP Cube adds 5 kWh modules within a stack, up to 40 kWh per unit. Powerwall 3 takes up to three 13.5 kWh Expansions, which add energy but not power.
Which has the better warranty?
EP Cube lists over 80% capacity for 10 years or 6,000 cycles. Tesla’s datasheet lists a 10-year warranty. Read each maker’s warranty document for the end-of-term capacity and conditions.
Do I need solar for either one?
Both can charge from the grid and provide backup. Without solar, though, neither can recharge during a long outage. See home battery backup without solar.
Bottom Line
Choose EP Cube 2.0 if you want storage sized in 5 kWh steps, up to 40 kWh in one stack, with strong solar input. Choose Tesla Powerwall 3 if you want full 11.5 kW output from a single compact unit, a 15.4 kW off-grid option and Tesla’s installer network. Either way, get at least two quotes and compare price per usable kWh and per kW.