High-Capacity Battery Backup: 10kW Off-Grid Solar System in Grand Case, Sint Maarten

Located in the Grand Case District of Sint Maarten, this project delivered a 10kW Split-Phase Off-Grid Solar System for a two-story, 5-bedroom, 2-bathroom standard home. Designed to address frequent power outages during the hurricane season, the system provides reliable backup power to ensure uninterrupted household operations in extreme weather conditions.

• The electricity bill is extremely high: The electricity price in Saint Martin has remained between 0.30 and 0.35 USD per kilowatt-hour for a long time, and the monthly bill easily exceeds 400 USD when air conditioning is turned on during the summer
  
• Frequent power outages: The island's aging power grid, compounded by hurricane season, often experiences voltage fluctuations and unexpected blackouts, leading to repeated damage to sensitive household appliances (such as refrigerators and computers)

The homeowner ultimately decided to adopt a fully off-grid solution, no longer relying on the public power grid but achieving 100% self-sufficiency through a solar+energy storage system

System Configuration

According to the Saint Martin Electrical Standard, a typical household requires a 120/240V split-phase power supply—where 120V is used for lighting, outlets, and small appliances, while 240V is allocated for high-power devices (air conditioners, ovens, water pumps). To this end, we have designed the following system configuration

The system's total energy storage capacity is 32 kWh, sufficient to cover the basic power needs of the villa during nighttime and rainy days. In the event of prolonged overcast or rainy weather, the inverter's built-in generator interface allows for quick connection to a backup generator for charging

Installation Process: Three Days of Efficient Delivery

Upon receiving the goods, the installation team promptly scheduled an on-site installation. On the first day, the roof bracket was installed, and the roof dimensions were measured to plan the installation and placement positions. The track was secured to ensure structural stability without damaging the roof waterproofing, while the wiring was routed through pre-embedded roof conduits into the indoor equipment room. On the second day, the inverter, lithium battery, and other equipment were installed. Due to the use of a split-phase inverter, the AC output was directly connected to the L1/L2/N/PE busbars of the villa's main distribution box, replacing the original grid input. Additionally, the original electric meter and grid connection were retained as an emergency backup (the inverter supports grid bypass input, allowing manual switching by the user)

The next day, debugging and solar system training were conducted, with guidance provided to the client on usage

The Sunchees 10kW Split-Phase Inverter delivers true phase-separated output: L1-N = 120V, L2-N = 120V, L1-L2 = 240V, eliminating the need for an external transformer and ensuring easy installation and operation