Indoor horticulture is gaining importance as a cost-effective method to meet the demands of a growing population. Modern day farmers are showing more interest in hydroponic farming to reduce the consumption of water and are always exploring ways to maximize crop yield. Indoor horticulture is dependent on artificial lighting for illumination to sustain plant growth and development. LED lighting is most suited for horticulture due to its tunable spectral characteristics, miniature size and energy efficiency. Energy efficiency of LED lighting for horticulture refers to ability of the light source to convert electrical energy into radiation that promotes photosynthesis. In this work, the role of photosynthetic luminous efficacy of radiation and photosynthesis action factor discussed with respect to energy efficiency of LED lighting for horticulture. Using mathematically analysis effectiveness of light produced by white LEDs, sunlight, purple LEDs and blue-red LEDs in inducing photosynthesis is discussed. Study showed that photosynthetic performance is highest when a combination of blue and red lights illuminate plants. The effect of white LED lighting and daylight is only a fraction when compared to blue-red light combination. Overall, for better photosynthetic performance it is preferred that lighting is provided using a mix of blue and red lights.