In this guide
What’s in the Pack
The SKU is IG-ES-Alpha-M5-27.98kWh, and it’s a genuinely simple bill of materials compared to the multi-module stacks we’ve covered in other brand guides:
Inverter
- 1× AlphaESS SMILE-M5-S-INV — 5kW single-phase hybrid, 2 MPPT / 2 strings
- AS4777.2:2020 compliant
- 10-year product warranty
Battery
- 2× SMILE-M-BAT-13.9P — 13.99kWh each, 100% DOD
- 1× extension box for the second battery, with top cover and connecting plates
- 27.98kWh total, fully usable
AlphaESS also sells the SMILE-M5-S-INV with a smaller 5kWh battery module (SMILE-M-BAT-5P), stackable up to six modules for 30kWh — a different battery line to the one in this bundle. This guide covers the 13.99kWh configuration specifically, since that’s what’s in this pack.
The 5kW + 27.98kWh Build
100% Usable, Two Units, Done
No cell balancing across half a dozen small modules, no multi-column floor plan — just one inverter and two batteries, and every kWh of the 27.98kWh is usable.
Why 27.98kWh Specifically
Two 13.99kWh modules is the maximum this battery line supports — AlphaESS’s own datasheet caps the SMILE-M-BAT-13.9P at 1–2 modules in parallel, so 27.98kWh isn’t a size you choose from a range, it’s the ceiling of what this exact product can do.
The Extension Box Explained
The first SMILE-M-BAT-13.9P mounts directly to the inverter. Every battery after that needs its own extension box — in this case, one box for the second battery.
Full Spec Table
Inverter — SMILE-M5-S-INV
| Spec | Value |
|---|---|
| Nominal output power | 5kW |
| MPPTs | 2 (16A max per MPPT) |
| Max PV input power | 10kWp |
| Phase | Single |
| Backup | UPS-style, built-in |
| Dimensions | 620×240×412mm |
| Weight | 19.5kg |
| Standard warranty | 10 years |
Battery — SMILE-M-BAT-13.9P (×2)
| Spec | Value |
|---|---|
| Nominal / usable capacity (each) | 13.99kWh / 13.99kWh (100% DOD) |
| Total (2 modules) | 27.98kWh |
| Max charge/discharge current | 105A / 105A |
| Chemistry | LFP |
| Dimensions (each) | 620×240×710mm |
| Weight (each) | 115kg |
| IP rating | IP65 |
| Max modules in parallel | 2 (hard ceiling) |
| Warranty | 10 years |
Source: AlphaESS AU official SMILE-M5 product page.
Perth & WA Rebates for This System
27.98kWh usable spans the first two federal rebate tiers cleanly. Figures last verified 15 August 2026.
Federal Cheaper Home Batteries Program
13.98kWh × $151 = $2,111
Total: roughly $5,639
WA Residential Battery Scheme
Capped at 10kWh regardless of actual battery size: $130/kWh up to $1,300 for Synergy customers, $380/kWh up to $3,800 for Horizon Power customers. See our WA battery rebate guide for full eligibility detail.
Stacked together: roughly $6,939 combined for a Perth (Synergy) customer, or $9,439 for a Horizon Power customer in regional WA.
Installation Compliance in WA
AS/NZS 5139 governs placement, clearances and mechanical protection. At 115kg per battery, both units need a hard, level, load-rated wall or floor fixing, and if the install site is a garage or carport where a vehicle could strike the unit, expect a mechanical barrier like a bollard as part of the job.
Who This System Suits
Right for: single-phase homes wanting a clean, contained install
This is one of the simplest battery installs in our range — two units, no complex module stacking, 100% usable capacity, and a capacity AlphaESS has explicitly sized around the current rebate structure. It’s also our VPP-preferred brand with the deepest install history in WA.
Worth knowing: it’s a fixed ceiling, not a scalable platform
27.98kWh is the maximum for this exact battery line. If you think you might want to expand past that later, our Growatt ALP/APX guide and GoodWe ESA guide cover platforms that scale considerably further.
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Frequently Asked Questions
- Why is the AlphaESS SMILE-M5 battery exactly 27.98kWh?
- It’s two SMILE-M-BAT-13.9P modules at 13.99kWh each, which is the maximum this specific battery line supports. AlphaESS markets this exact configuration as rebate ready, since it sits within the same federal rebate band as a 28kWh system.
- Do I need an extension box for a second AlphaESS battery?
- Yes. The first battery mounts directly to the inverter, but every additional battery needs its own extension box with top cover and connecting plates, supporting either a front or stackable arrangement.
- Is the AlphaESS SMILE-M5 battery 100% usable?
- Yes. The SMILE-M-BAT-13.9P is rated at 100% depth of discharge, so the 13.99kWh nominal figure per module is also the usable figure.
- What’s the difference between the SMILE-M5 with 13.99kWh batteries and the 5kWh module version?
- The same inverter can pair with a smaller 5kWh module (stackable to 30kWh across up to 6 modules) or the larger 13.99kWh module (stackable to 27.98kWh across up to 2 modules). This guide covers the 13.99kWh configuration.
- Does the AlphaESS SMILE-M5 qualify for WA and federal battery rebates?
- Yes, provided the specific model is on the current Synergy or Horizon Power Supported Solutions list and the install meets VPP enrolment requirements. Both rebates stack.
