Powerwall 2 versus Powerwall 3: what changed
The Powerwall 3 keeps the Powerwall 2's 13.5 kWh and changes almost everything around it: more than twice the power, a solar inverter inside the case and a different cell chemistry. This article sets out what those changes mean in a real home, what stays the same, and what an owner of a 2 does and doesn't gain by moving.
Same energy, very different power
Both units store 13.5 kWh of usable energy. What differs is how fast they can deliver it. A Powerwall 2 supplies 5 kW continuously, with a short peak of 7 kW. A Powerwall 3 supplies 11.5 kW continuously.
In a home that difference shows up in three places:
- Big loads together. An electric shower alone can draw 8–10 kW. On a Powerwall 2 the battery covers 5 kW of that and the grid supplies the rest, at whatever the price is at the time. A Powerwall 3 covers the shower and the oven at once from the battery.
- During a power cut. Off-grid, there is no grid to make up the difference. A Powerwall 2 home has to avoid running the shower, the oven and the kettle together or the system trips. A Powerwall 3 home mostly doesn't notice.
- Peak export. On a tariff with a premium export window, a Powerwall 3 can push energy out faster, though most homes are held back by a 3.68 kW export limit long before either battery is. See the 3.68 kW export limit.
Charging is a different matter. The rate at which either unit fills from the grid is set by the system and is usually well below the discharge rating, so a Powerwall 3 doesn't fill an overnight window in half the time. Check what your own system shows when it charges hard.
Solar: built in versus alongside
Powerwall 2: AC-coupled
A Powerwall 2 has no solar input. The panels connect to a separate solar inverter, which converts their DC to AC for the house, and the Powerwall takes surplus AC and converts it again to store. It works with any solar inverter, which is why so many were fitted to existing solar installations. The cost is an extra conversion on every solar kWh stored, and a second box on the wall with its own warranty and its own limits.
Powerwall 3: DC-coupled
A Powerwall 3 has the solar inverter inside. It accepts up to 20 kW of panels across six separate DC inputs, each with its own maximum power point tracker. Solar goes straight to the cells with one DC-to-DC step, saving a conversion, and each roof aspect gets its own tracker so a shaded east string doesn't drag down a sunny west one. For a new installation it means one box instead of two. For an existing installation with a working solar inverter, it means the old inverter becomes redundant, or stays on as an AC-coupled extra feeding the same battery.
Six strings also produce six sets of data. The Powerwall 3 reports volts, amps and watts per string, which is how you find out that one string is underperforming. That data has a catch, covered below.
Chemistry
The Powerwall 2 uses NMC cells; the Powerwall 3 uses LFP. In general terms, LFP tolerates more cycles, is less bothered by sitting full and is more stable at high temperature, at the cost of lower energy density, which is why the Powerwall 3 is heavier for the same 13.5 kWh. For an owner the practical implications are modest: both chemistries are managed by the system, both are warranted for a similar term, and both will outlast most people's expectations if kept cool. The longer cycle life of LFP matters most to someone planning to cycle twice a day on a tariff with several cheap windows. See does daily cycling wear a battery out.
Expansion, the gateway and backup
A Powerwall 2 system grows by adding more Powerwall 2 units, each a complete battery with its own inverter, each adding 5 kW and 13.5 kWh. A Powerwall 3 grows with DC expansion units: extra cells that share the first unit's inverter, so each adds 13.5 kWh but not a second 11.5 kW. Both approaches work; the Powerwall 3 route is cheaper per kWh, and the Powerwall 2 route adds power as well as energy.
Both need a gateway or backup switch between the house and the grid to island the home during a power cut, and both then run the house from the battery until it reaches the backup reserve or the grid returns. The reserve setting works identically. In a cut, the Powerwall 3's higher power is the difference between managing carefully and not thinking about it. See backup reserve explained.
Can the two be combined? Tesla has said a Powerwall 3 can be added to some existing Powerwall 2 systems, but support varies by region and by the age of the existing installation, so treat it as a question for an installer rather than an assumption.
What stays the same
| Powerwall 2 | Powerwall 3 | |
|---|---|---|
| Usable energy | 13.5 kWh | 13.5 kWh |
| Continuous power | 5 kW (7 kW peak) | 11.5 kW |
| Solar connection | AC, via a separate inverter | DC, built-in inverter, six strings, up to 20 kW |
| Cell chemistry | NMC | LFP |
| Expansion | More Powerwall 2 units | DC expansion units |
| App modes | Self-Powered, Time-Based Control, reserve, grid charging, export setting | The same |
| Cloud interface | Tesla's | The same |
The last two rows are the point. The Tesla app offers the same modes and the same settings on both, and everything written about time-based control applies equally. A tariff, a rule or a plan that works on a Powerwall 2 works unchanged on a Powerwall 3. The battery's behaviour on a smart tariff is decided by capacity and settings, and the capacity is the same.
Upgrading from a 2: what you gain and what you don't
An owner of a Powerwall 2 with a working solar inverter gains, from a move to a 3: power for big loads and outages, one fewer AC conversion on stored solar, per-string monitoring, cheaper future expansion and LFP's longer cycle life.
They don't gain any storage. The everyday saving on a tariff comes from shifting 13.5 kWh from cheap hours to dear ones, and that number hasn't moved. Nor does the 2 become obsolete: it receives the same software, offers the same modes and is supported by the same apps. For most owners of a healthy Powerwall 2, the better upgrade is a second unit, or better rules, rather than a replacement. A 3 makes most sense when the solar inverter needs replacing anyway, when the array is being enlarged past what the old inverter takes, or when outage power genuinely matters.
How they look to third-party apps
Through Tesla's cloud interface, the two are nearly indistinguishable. Both report the same power flows, energy totals, battery percentage and settings, and both accept the same commands. An app that reads and controls a Powerwall doesn't need to know which one it is talking to.
The exception is per-string solar. The Powerwall 3 reports each string's volts, amps and watts only over the home network, through its local gateway, and not through the cloud at all. So an app can only show per-string data from a device on the same network as the Powerwall, and the interface it uses is not one Tesla documents. Anyone comparing apps on that feature should ask where the data comes from.
In SunHarvest
SunHarvest treats both generations the same through Tesla's cloud: the same flow diagram on Home, the same rules and the same AI planner. Settings › Site shows which hardware, capacity and peak power Tesla reports for your site. Per-string solar is the one feature that needs a Powerwall 3: the Android app's local gateway card, part of Pro, enrols the phone on your home network and reads each string while the app is open at home, and you can name the strings after your PV arrays so the tiles on Home say "East roof" rather than "String 2". Tesla doesn't document that interface, so a Powerwall update could change it.
General information, not financial or electrical advice. Tariff terms, prices, warranties and connection rules change and differ by supplier, region and installation; check the current documents for yours. SunHarvest is not affiliated with Tesla or Octopus Energy.