While it's true that HPS bulbs and metal halide bulbs are both high intensity discharge lights, HPS lights produce a more efficient light that has a more ideal light spectrum for growing. 10 percent more efficient than metal halide lights, HPS lights focus a very bright reddish yellow light and completely omit blue or violet light, creating ideal growing light for growing and flowering.

In fact, HPS bulbs are 10 to 15 percent more efficient than a metal halide light. They also produce a higher amount of lumens per bulb, which measures the amount of light used against how much electricity you are using. Typically, HPS lights produce a yellow-orange light that has 97 to 150 lumens per watt. Metal halide lights typically produce 67 to 97 lumens per watt.

That added percentage adds up to more beautiful plants and a healthier harvest of vegetables from each plant. It also makes HPS lights more environmentally beneficial by providing better lighting for your plant with less electricity. The extra electrical savings are good not only for your wallet, but are also beneficial to the earth itself, leaving less of a carbon footprint. The impact of these lights is undetectable.

Keep in mind that High Pressure Sodium lamps need to be changed every year or so as they dramatically lose their performance after a growing season or two, resulting in less efficiency and more energy use. Older lights grow less healthy plants that produce lower yields.

High Pressure Sodium bulbs can also run considerably hot, so it's always good to keep them a decent distance away from plants to avoid scorching them. Don't move the lights too far from the plants, however. The amount of light weakens two fold as lights are placed away from plants. A light placed far away from a plant will give the plant considerably less light the farther away it is. It's always best to keep plants as close as the light can get without scorching or damaging the plants. Good fans and adequate ventilation can keep plants cool and healthy.

High Pressure Sodium can be used to produce a healthy indoor garden, making year round fresh vegetables a reality. They are considerably less expensive than LED lights. While less efficient than LED, they work a little better than metal halide. With a little practice, you can learn the exact amount of light your plants need to grow and bloom beautifully, reaping a healthier harvest as your thumb grows greener.

It is also important to not put the HID light source to close to your plant. Since HID systems put off more heat than fluorescent lighting and LEDs. This could cause the plant to get burnt. Lower wattages should be placed 2-3 ft above the plant. Higher wattages (400W-1000W) should be place 4 to 6 feet from your gardening area.

HPS is optimal in the flowering and budding stages. They need to be supplemented by a light source to will help in the "growth phase" Metal Halide and Fluorescent work extremely well. If not, your plants will tend to get "leggy" and appear unhealthy.