Tesla Powerwall 3 vs Sigenergy SigenStor vs AlphaESS SMILE-G3

What this comparison covers

This guide is for a UK household adding storage to solar panels it already owns. Compare only the battery addition's incremental cost; the existing solar installation is not a new investment. These three Battery Payback product families are examples for examining a quote, not a market-wide ranking. The precise model, module count, inverter route, phase, metering, gateway and backup scope determine the proposed system. Manufacturer documents cannot replace a site-specific installer assessment.

The current calculator does not calculate a joint new solar-and-battery purchase, grid charging, dynamic tariff optimisation, the monetary value of backup power, reserve or grid-service revenue, or individual electrical and safety design. Those benefits may matter to a household; they need separate assessment.

Powerwall 3 vs SigenStor vs SMILE-G3

The figures below retain each source's measurement boundary. Battery energy is not annual AC delivery to your home. Nominal and usable energy, continuous and peak power, and AC and DC ratings must not be interchanged. Ask the installer to identify the exact revision and components on your quote.

Tesla Powerwall 3

Identify the Powerwall 3 model and configured single-phase AC rating, plus any Expansion and Backup Gateway 2. Tesla's UK sheet distinguishes an integrated solar inverter from the separate gateway required for its backup arrangement. The existing inverter plan and backup scope can change installation cost. Read the detailed Powerwall 3 guide.

Sigenergy SigenStor

A SigenStor name does not fix the Energy Controller, phase or BAT module count. Its module sheet's DC battery limits are not the continuous AC output of a completed system. Ask how the controller, existing solar inverter, metering and any gateway are connected and priced. Read the detailed SigenStor guide.

AlphaESS SMILE-G3

Specify S5 hybrid or B5 AC-coupled inverter and each BAT identifier. The reviewed V08 sheet and later V2.3 brochure show different module generations, so a family-level capacity would mislead. The inverter route, module choice and optional backup work affect cost. Read the detailed SMILE-G3 guide.

Which battery fits an existing solar system?

There is no configuration-independent winner for an existing solar system. Ask whether your present inverter stays, is replaced or needs a separate battery inverter or controller. Confirm how energy is measured, which gateway is mandatory, whether backup is included and exactly which loads it serves. Check whether each quoted number is single-phase or three-phase, AC or DC, and whether the equipment can be installed in the proposed locations.

The installer must assess property eligibility, electrical design, product and configuration suitability, safety, permissions, notifications, compliance, installation and commissioning. Battery Payback cannot approve an installation for a particular home.

What changes the installed cost?

Compare the whole incremental cost of adding storage, including the battery unit and exact modules; inverter or controller; gateway, backup and measurement equipment; keeping, removing or replacing existing hardware; mandatory electrical work; installation and commissioning. All mandatory costs at installation belong in the additional installed cost. Ask what the offer excludes and price optional upgrades separately.

Request ongoing monitoring, subscription and service charges and any known later replacement or end costs. The calculator's additional annual costs input represents a real, constant yearly incremental expense. It does not model a later one-off battery replacement or separate end costs. If a mandatory replacement or material end cost is known, make a broader comparison before deciding. Read the installed-cost guidance for existing solar.

Which option has the strongest payback?

There is no product-level payback winner without a like-for-like installed quote and the same household assumptions. Brand is not a calculator input. Additional installed cost, realistic first-year annual AC energy delivered to home loads, the avoidable purchase price and the net export value forgone all matter. Stored solar may avoid a purchase while giving up export income. Use comparable real-price and annual time bases for every offer.

Operating and known later costs, whole-system AC efficiency, degradation, life, analysis horizon and real return target can change the answer. Extra capacity need not yield extra usable energy; paying for unused capacity can weaken the result. Negative net savings, negative NPV and no payback remain valid outcomes. The calculator compares scenarios, not brands, and it does not decide technical suitability. Open the calculator to compare your assumptions.

Compare the same illustrative assumptions

All rows use the current Load illustrative example inputs: £4,600 additional installed cost, 30p/kWh avoided electricity purchase price, 4.1p/kWh forgone export value, 90% whole-system AC efficiency, £0 additional annual costs, 1% annual delivered-energy decline, 12-year analysis period, 12-year assumed operating life and 3% real annual return target. Warranty, solar surplus, baseline imports and capacity are unknown. The energy boundary is AC solar that would otherwise have been exported and AC battery delivery to home loads that would otherwise have been bought.

These are illustrative inputs, not product prices, UK averages, tariff forecasts or promises of savings. The same validated inputs give the same calculation for any product name. The year-end payback boundary is the end of the first year when cumulative cash flow has recovered and stays non-negative through the rest of the analysis period. The interpolated payback estimate assumes savings build evenly during that payback year. Neither is a discounted payback period or a promise of when recovery will occur.

Questions to ask about each quote

Ask the installer to confirm the exact model, modules, inverter and gateway arrangement in writing. Use a like-for-like itemised quote checklist:

1. List the exact product model, battery module IDs and quantities. Label nominal and usable capacity, continuous and peak power, and each AC/DC and phase boundary.
2. State whether the existing inverter stays; identify every replacement inverter, battery inverter or controller, gateway, meter and backup component, plus the loads backed up.
3. State the full additional installed cost, commissioning and mandatory work. Separate optional items, exclusions, monitoring, subscriptions, servicing and known later replacement or end costs.
4. Provide the applicable warranty document, region and version, including years, throughput, retained-capacity measurement and material conditions. Identify commissioning, monitoring and support responsibilities.
5. Explain the annual battery-use estimate using the home's solar exports and later demand. State the efficiency measurement boundary and evidence for factual product or accreditation claims.

Next step: compare your own quote

Use your own itemised quote and household use assumptions in the calculator; it compares financial scenarios but does not choose a product. Review the system design with a qualified installer before deciding.

Open the battery payback calculator

• Use the itemised quote checklist
• Read the Tesla Powerwall 3 guide
• Read the Sigenergy SigenStor guide
• Read the AlphaESS SMILE-G3 guide