Solar Balance of System

trackers · wiring · protection · interconnection

Modules and inverters are now cheap commodities; the hardware around them is not. Balance of system decides whether a plant passes inspection, stays online and survives the weather.

Balance of system along the solar power path, in three rows. Array: trackers, modules, connectors and combiner box. Protection and conversion: rapid shutdown devices, DC disconnect, inverter and AC disconnect. Interconnection: transformer, switchgear, meter and the utility grid. Everything except modules, inverter and grid is balance of system; monitoring, conduit, grounding and labeling run through every row. ARRAY Trackers Modules Connectors Combiner box PROTECTION AND CONVERSION Rapid shutdown DC disconnect Inverter AC disconnect INTERCONNECTION Transformer Switchgear Meter Utility grid Gold: balance of system. Gray: module, inverter and grid. Monitoring, conduit, grounding and labeling run through every row.
Leading tracker maker
Nextpower
Utility DC voltage
1,500 V
Governing code
NEC 690, 705
Hub
Energy

Finding

With module prices below cost, balance of system and labor are now the largest share of what a solar plant costs

Module prices fell below manufacturing cost in 2024, so trackers, wiring, protection, interconnection equipment and installation labor dominate installed cost. They also dominate failures: connector mismatches, water ingress, cable damage and tracker stow failures cause more lost energy than cell defects.

Balance of system is where the electrical code is implemented: NEC Article 690 for PV systems, Article 705 for interconnection, 690.12 for rapid shutdown on buildings, and 690.11 for DC arc-fault protection. At utility scale, the move from 1,000 V to 1,500 V DC halved the number of combiners and home runs per megawatt, and single-axis trackers became the default ground mount in the US because they add 15-25% energy for a small cost premium.

Trackers are the one BOS stage where US companies lead: Nextpower (renamed from Nextracker in 2025) and Array Technologies are the two largest suppliers worldwide, ahead of GameChange Solar and Chinese makers Arctech and Trina Tracker. Large transformers and switchgear are the long-lead items; transformer lead times past two years now set many solar interconnection dates.

Components

What balance of system includes

Solar balance of system components
CategoryComponentsLeading suppliersCode or standard
MechanicalSingle-axis trackers, fixed-tilt racking, roof attachments, pilesNextpower (formerly Nextracker), Array Technologies, GameChange, Arctech, Trina Tracker, IronRidge, UniracASCE 7 wind and snow loads; UL 3703, UL 2703
DC electricalPV wire, MC4-type connectors, combiner boxes, fuses, DC disconnectsStaubli, Amphenol, Shoals, Eaton, BentekNEC 690; UL 6703 connectors
Module-level and safetyRapid shutdown devices, arc-fault and ground-fault detectionTigo, APsystems, SolarEdge, EnphaseNEC 690.11, 690.12
AC and interconnectionAC disconnects, step-up transformers, switchgear, revenue meters, relaysEaton, Schneider Electric, Siemens, ABB, Hitachi EnergyNEC 705; IEEE 1547
Monitoring and controlsGateways, SCADA, weather stations, power plant controllersEnphase, SolarEdge, AlsoEnergy (Stem), Huawei, SungrowIEEE 2030.5; NERC requirements at utility scale
Pathways and groundingConduit, trenching, cable trays, grounding and bonding, labelingAtkore, nVent, PanduitNEC 250, 690.31

Trackers

Single-axis tracker makers

Trackers are the largest mechanical BOS line in a ground-mount plant and the one where US companies lead.

Solar tracker makers
CompanyHQProductsNotes
NextpowerUS (Fremont, California)NX Horizon single-axis trackers, eBOS, foundationsLargest tracker supplier worldwide; renamed from Nextracker in 2025
Array TechnologiesUS (Albuquerque, New Mexico)DuraTrack, OmniTrack and SkyLink trackersBought STI Norland (Spain) in 2022
GameChange SolarUS (New York)Genius Tracker, fixed-tilt rackingLarge share of US fixed-tilt and tracker projects
Arctech SolarChina (Kunshan)SkyLine and SkySmart trackersLargest Chinese tracker maker; strong in India, Middle East and Latin America
Trina TrackerChina (Changzhou)Vanguard and Agile trackersTrina Solar unit; formerly Nclave in Spain
PV HardwareSpain (Valencia)Axone and Monoline trackersStrong in Europe and Latin America
SoltecSpain (Molina de Segura)SF7 and SFOne trackersIn financial restructuring since 2024
FTC SolarUS (Austin, Texas)Voyager and Pioneer trackersSmaller US maker with one-module-in-portrait design

Why it matters

Where balance of system wins or loses

Balance of system outcomes
OutcomeBOS factor
ReliabilityConnector matching, sealing, strain relief and cable routing prevent the most common field failures
SafetyDisconnects, grounding, bonding, rapid shutdown and arc-fault detection reduce shock and fire risk
Energy yieldTracker accuracy, voltage drop, thermal derating and string mismatch set losses
ServiceabilityAccess, labeling and standard parts cut O&M time and cost
ComplianceMost code requirements are met, inspected and verified in BOS hardware

Sources

Sources and scope

Scope
Solar Balance of System
Sources
NFPA 70 (NEC) Articles 690 and 705; IEEE 1547; vendor data
Updated
October 2026