Transparent heaters (THs) are widely used in applications such as deicing, defogging, and thermal management, requiring high transparency, low sheet resistance and structural durability. This study investigates the design, fabrication, and performance of ZnO/Cu/SiO₂ (ZCS) THs, with a particular focus on thermostability. By employing a dielectric/metal/dielectric configuration with Cu as the metallic layer, ZCS heaters offer a cost-effective alternative to indium tin oxide and Ag-based THs. The optimized ZCS structure, comprising ZnO (20 nm)/Cu (6 nm)/SiO₂ (80 nm), demonstrates exceptional performance, achieving high visible transparency (maximum of 94.8 % and average of 86.3 %), low sheet resistance (∼10 Ω/sq or less), and rapid thermal response. The heaters exhibit excellent stability during prolonged operation and repeated on-off cycling at elevated temperatures of ∼200 °C due to the planar structure of heating element. This remarkable thermostability far exceeds that of THs consisting of network-structured Cu nanowires, which fail at temperatures below 90 °C. Under bias voltage sweeping, the ZCS TH with an 8-nm-thick Cu layer undergoes gradual and irreversible structural degradation, beginning with localized void formation and progressing to full-scale solid-state dewetting and agglomeration of Cu layer, ultimately failing at ∼ 330 °C. These findings establish ZCS heaters as versatile and cost-efficient alternatives for high-performance transparent heating in demanding environments and present a pathway for further structural enhancement.