The Tesla Powerwall 3 and the Sigenergy SigenStor sit at the centre of the UK home-battery conversation, and they take opposite approaches to the same job. We install both, which puts us in a useful position: we have no reason to talk one up over the other. What follows is a comparison built on the manufacturers’ published figures, and an honest account of which homes each one suits.
The short answer: the Powerwall 3 is a single, fixed 13.5 kWh unit with an integrated solar inverter, high continuous output and the strongest published retention warranty of the lines we install. The SigenStor is a modular tower you size to your home — roughly 6 or 9 kWh at a time — with an optional DC EV-charging module nothing else in this class offers. Neither is “the best”. They are different answers to different questions.
The published figures, side by side
| Sigenergy SigenStor | Tesla Powerwall 3 | |
|---|---|---|
| Storage format | Modular: 6.02 kWh or 9.04 kWh LiFePO4 battery modules, stacked in a tower; multiple towers can run in parallel | Fixed: 13.5 kWh per unit; up to 4 units supported on one site |
| Continuous power | 3,000 W (6.02 kWh module) or 4,600 W (9.04 kWh module) max charge/discharge per module; hybrid inverters from 3.0 kW to 12.0 kW single-phase | Configurable up to 11.04 kW continuous discharge; up to 5 kW continuous charge |
| Solar input | Integrated hybrid inverter, 2–4 MPPTs depending on model; max inverter efficiency 97.6–98.0% (single-phase) | Integrated solar inverter, up to 20 kW DC across 3 MPPTs; 97.5% solar-to-home efficiency |
| EV charging | Optional DC module: 12.5 kW or 25 kW, CCS2, bi-directional/V2X-ready (subject to the EV’s capability) | Not built in — EV charging is a separate wallbox |
| Backup power | Supported with Sigenergy gateway hardware, designed per home | Whole-home or partial backup via Tesla Backup Gateway 2 |
| Warranty length | 10 years (battery modules and hybrid inverter); EV DC module 3 years | 10 years |
| Warranted retention | 60% of usable energy at 10 years, or a per-module minimum throughput figure, whichever comes first | 80% at 10 years for UK installations, unlimited cycles for solar self-consumption, time-based control and backup |
| Warranty conditions | Internet connection required; extended disconnection reduces the term to 5 years | Internet connection required for the full term; Tesla honours at least 4 years regardless |
| Enclosure | IP66, smart air cooling | IP67 battery and power electronics, IP55 wiring compartment |
| App | mySigen | Tesla app |
Figures from Sigenergy’s SigenStor product specifications and European warranty document, and Tesla’s UK Powerwall 3 datasheet and European warranty (UK terms). Product lines change — we confirm current models and terms at quote stage.
Capacity: fixed block vs building blocks
A Powerwall 3 gives you 13.5 kWh whether you need it or not. For a typical family that is a well-judged number — enough to carry an evening and overnight on stored solar or cheap-rate charge — but a smaller household may never cycle all of it, and capacity you do not cycle is capital that never pays you back.
The SigenStor starts smaller. One 6.02 kWh module suits modest usage today, and because modules stack and auto-connect, adding capacity later is an engineer visit rather than a system replacement. Tesla’s answer to growth is adding a whole second Powerwall — supported up to four units, but in 13.5 kWh strides rather than 6 or 9 kWh steps.
If your usage is stable and substantial, the fixed block is a clean, cost-effective answer. If your usage is about to change — EV on order, heat pump on the horizon, extension planned — the modular tower fits the trajectory better.
Power: what actually runs at once
Output is where the Powerwall 3 stretches its legs: configurable up to 11.04 kW of continuous power (your DNO connection permitting) and the muscle to start heavy motor loads up to 185 A LRA. Electric shower, oven and car charger simultaneously is a realistic scenario for it.
A SigenStor’s output depends on configuration — each battery module contributes 3.0 or 4.6 kW, and the single-phase hybrid inverter range tops out at 12.0 kW — so a well-specified stack competes closely, but a single-module starter system will not match a Powerwall’s output. That is not a flaw; it is the trade-off of starting small, and it is exactly the sort of thing your installer should spell out before you buy.
The EV question
Here the SigenStor has something genuinely unusual: an optional DC charging module rated at 12.5 kW or 25 kW that draws directly from the battery and solar array, with bi-directional (vehicle-to-home, vehicle-to-grid) capability where the car supports it. Against the 7 kW AC wallbox most UK homes install, 12.5–25 kW DC is a different league — with the caveats that the module carries a shorter 3-year warranty and V2X depends on your vehicle.
Tesla’s ecosystem keeps EV charging as a separate product. That is no hardship — we fit EV chargers alongside batteries routinely — but it is more wall hardware and another install, and it will not reach DC speeds at home.
Warranties: read the retention line, not just the years
Both systems carry 10-year warranties. The difference is what is guaranteed at year ten. Tesla warrants 80% of the original 13.5 kWh for UK installations with unlimited cycles for normal home use — the strongest published retention figure among the lines we install. Sigenergy warrants 60% of usable energy, or a minimum throughput-energy figure per module, whichever arrives first.
Both require an internet connection to keep the full term alive — Sigenergy’s term adjusts to 5 years if the system is offline for more than a year cumulatively; Tesla commits to at least 4 years if connectivity or registration lapses. None of this is small print to skim: it is the difference between what the brochure implies and what the manufacturer will actually stand behind. We put both documents in front of customers before they choose.
Which suits your home?
Choose the Powerwall 3 profile if: your consumption is already substantial and stable; you want maximum output from one unit; whole-home backup is a priority; or the warranted 80% retention is what lets you sleep at night.
Choose the SigenStor profile if: you want to start smaller and grow in affordable steps; you are planning around an EV and want DC charging or V2X in your future; or you prefer one slim tower handling inverter, storage and EV charging together.
There is no universal winner — the right answer is a function of your usage data, your plans and your property, which is why we survey before we quote. If a battery is not the right spend for you at all, we will say that too.
Talk it through
We install both systems, and we will model each against your actual consumption rather than a national average. Request a free quote or call 0204 547 1892 — no pressure, just clear advice. You can read more on each product page: Sigenergy SigenStor and Tesla Powerwall 3, or see the whole range on battery storage.