Very little. The Trimlight 3L bulb draws 0.9 watts each; the Classic draws 0.6 watts each. On a typical 200-linear-foot Middle Tennessee roofline (~50 bulbs), the whole system draws 30–45 watts — less than a single incandescent bulb. Most Northpoint Trimlight customers see about $5–$15 added to their monthly NES, MTEMC, Middle Tennessee Electric, or Duck River Electric bill running warm-white year-round at typical sunset-to-bedtime schedules.