Why Can't You Compare Home Battery Spec Sheets Line by Line?
Summary
Capacity, continuous power, efficiency, and warranty are the lines that matter, yet each brand measures them under different conditions. Tesla lists Powerwall 3 at 13.5 kWh nominal, Enphase lists IQ Battery 5P at 5.0 kWh usable, and their efficiency figures cover different paths through the system. The footnotes say what each number means, and they change how the table reads.
Capacity comes with conditions attached
The 13.5 kWh on the Powerwall 3 datasheet carries a footnote: measured at 25°C (77°F), at beginning of life, at 3.3 kW charge and discharge. The datasheet has no line labeled usable energy. Enphase does give usable capacity, 5.0 kWh, and explains in its footnote that this figure includes a 2% safety-critical limit held back for long outages, plus another 3% reserved for the battery electronics overnight. FranklinWH's aPower 2 product page says 15 kWh capacity without stating whether that is nominal or usable, and the company's datasheet PDF could not be read as text.
| Tesla Powerwall 3 | Enphase IQ Battery 5P | FranklinWH aPower 2 | |
|---|---|---|---|
| Capacity | 13.5 kWh nominal | 5.0 kWh usable | 15 kWh |
| Continuous output | 5.8 to 11.5 kW, by configuration | 3.84 kVA at 240 V | 10 kW |
| Efficiency | 89%, solar to battery to home or grid | 90% AC round trip | not listed |
| Chemistry | not listed | lithium iron phosphate (LFP) | LFP |
| Warranty | 10 years | 15 years or 6,000 cycles | 15 years or 60 MWh throughput |
| Solar connection | built-in PV input, 20 kW STC max, 6 MPPTs | AC-coupled | AC-coupled, per the aPower S page |
Efficiency numbers measure different trips
Tesla's 89% is labeled "Solar to Battery to Home/Grid" for a typical solar shifting use case. Enphase's 90% is AC into the battery and back out as AC at 50% of rated power, and the sheet adds a separate 96% DC round-trip figure. FranklinWH quotes up to 90.5% for its aPower S, defined as solar to battery to home or grid. Two of these start from solar, one starts from AC, and none is a direct match for another.
The maker states what the battery works with
SolarPanelX does not rule on which equipment can be combined. What the manufacturers themselves publish is this: Enphase lists IQ and M Series microinverters, IQ System Controller 3/3G, IQ Combiner 5/5C, and IQ Gateway as compatible with IQ Battery 5P, and notes that backup and off-grid operation is not supported on 208 V single-phase service. Powerwall 3 accepts PV directly at 60 to 550 V DC, and its Expansion unit is listed as compatible only with Powerwall 3.
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Sources
- Tesla — Powerwall 3 Datasheet (2025)
- Enphase — IQ Battery 5P Data Sheet (DSH-00010-11.0, 2025-05-06)
- FranklinWH — aPower 2 Home Battery Backup
- FranklinWH — aPower S Home Battery
We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.