Split-phase stand-alone grids - now easier than ever

The Smartformer is the complete solution for off-grid and battery back-up systems up to eight kilowatts. It acts simultaneously as AC distribution and a 120 V/240 V autoformer. The autoformer provides step-up and step-down options to supply loads with 120 V and 240 V using a Sunny Island and a Sunny Boy, with high efficiency over the entire power spectrum. Thanks to the pre-wired bypass function, the PV system can be easily bridged via a robust switch for maintenance. The optimized transformer overload protection and a load shedding relay provide extra protection to the system. The Smartformer makes the stand-alone power supply simple and reliable.



  • Pre-wired AC distribution board
  • Fast installation and commissioning


  • Bypass switch for direct grid operation
  • Load shedding relay to prevent deep battery discharge
  • Miniature circuit breakers for PV and load


  • Maximum efficiency of 99%


  • UL certified
  • Optimized overload protection
Technical Data Smartformer
General data  
Number of phases Split-phase
Rated voltage 120 Vac/240 Vac
AC voltage range betweenL₁and N / L₁ and L₂ 102 V ... 132 V / 204 ... 264 V
Rated frequency 60 Hz
Dimensions (WxHxD) / Weight 24.02 x 24.02 x 9.25 in (610 x 610 x 235 mm) / approx. 123.5 lbs (approx. 56 kg)
Idle power consumption 19 W (typical)
Nominal power transformer* 3.4 kVA
Transformer AC power for 30 min / 1 min 4.4 kVA / 8.8 kVA
Max. efficiency/CEC efficiency 99% / 98.8%
Hookup access Knockouts top: 2x 3/4”, 2x 1”, 2x 1 1/4”
bottom: 5x 3/4”, 3x 1”, 3x 1 1/4”
Connections for Sunny Island  
Maximum number and nominal voltage of Sunny Island 1 x 120 V (L1, N)
Rated power 7.2 kW
Current at rated values 48 A, 60 A
Fuses Circuit breaker K60A for AC2
PV plant connection  
Number of connections/nominal voltage 1 x 240 V (L1, L2, N)
Rated power / AC power at grid parallel operation 9.6 kW / 6kW
AC power in parallel grid operation 6 kW
AC current at rated values 40 A
Fuses 2 x miniature circuit breaker Z50A or Z25A, adaptable
Load connection  
Number of connections/nominal voltage 1 x 120 V/240 V (L1, L2, N)
Rated power / AC power at 40 °C 7.2 kW / 6.6 kW
Rated power / current between L₁ and L₂ 6.7 kW / 28 A
Rated power / current between L₁ and N 3.8 kW / 32 A
Rated power / current between L₂ and N 3.4 kW / 28 A
Current at rated values 32 A, 28 A (with activated bypass: 2 x 48 A)
Fuse Circuit breaker K40A (with activated bypass: K60A)
Grid / Generator connection  
Number of connections/ nominal voltage 1 x 120 V/240 V (L1, L2, N)
Rated grid input power 11.5 kW
AC input current 2 x 48 A
Fuse 2x miniature circuit breaker K60A
Ambient conditions  
Operating temperature range -13 °F ... + 122 °F (-25 °C ... +50 °C)
Humidity 0 - 100% (non-condensing)
Protection class NEMA Type 1
Certification and approval UL 1741
Warranty: 5/10/15/20 years yes/opt./opt./opt.
Integrated bypass for maintenance/load shedding relay/transformer protection yes/yes/yes
*Power that can be transfered from one leg to another  
Type designation SI-TD-BOX-10


Data sheet

SMARTFORMER FOR SUNNY ISLAND - Split-phase stand-alone grids - now easier than ever
Type: Data sheet
Language: English (US)
Document number: SMARTFORMER-DUS124616
Version number: 1.6
Installation Guide

Type: Installation Guide
Language: English (US)
Document number: SI_TDBOX-IA-eng-IUS122211
Version number: 1.1
Technical Description

SMARTFORMER FOR SUNNY ISLAND - Technical description / Descripción técnica
Type: Technical Description
Language: International
Document number: SI_TDBOX-US-TB-en_es-12
Version number: 1.2

Certificate of Compliance - SMARTFORMER FOR SUNNY ISLAND
Type: Certificate
Language: English (US)
Document number: SI-TD-BOX-10-ZE-CoC-UL-en-10
Version number: 1.0