How to switch from HID lighting to LED grow lightsThere’s more to a HID - LED switch than just finding a new bulb with the same wattage. If you’re looking to make the change, this guide will show you exactly how to swap HPS/MID bulbs to LEDs so you can get the same results, for a fraction of the price. ContentsEnergy useBrightnessLight usageHow to measure parWhy use par?Why use LEDs?To get started, we’re going to dive into definitions for wattage, lumens and PAR, so you know what you need to look for when shopping for LED grow lights. Wattage: Energy use The first mistake you can make when switching to LED is just looking at wattage. In fact, just relying on the wattage of each bulb could cause problems for your plants and their grow cycles. Wattage simply refers to the amount of energy that’s used by the light. It doesn’t relate to how bright the light can shine, or how much of the light can actually be absorbed by your plants. When switching from HID to LED, you need to focus more on the light’s performance, to ensure you’re giving your plants the best environment to thrive in. Lumens: Brightness The amount of light a bulb emits is referred to as lumens. The more lumens, the brighter the light. However, lumens still aren’t the measurement you should look for when switching to LED, as these bulbs can be incredibly powerful.To put it into figures, a 400-Watt HID light offers the same brightness (lumens) as a 194 Watt LED. Yep, an LED bulb can provide the same brightness using half the energy.As we mentioned above, lumens still aren’t the only factor to look for when swapping HID lights out for LEDs. Even if the light is just as bright, it doesn’t mean the plants are getting all the light they need to thrive. Lumens don’t indicate how much light the plant can use. For that, you’ll need to look at the PAR rating. PAR/PPFD – Photosynthetic Active Radiation: Light Usage PAR refers to the amount of light your plants can actually use for photosynthesis. As we all know, plants can’t grow without photosynthesis, so if you want to make sure your they have the best chance of growth, you need to check the PAR rating for any grow light you choose. In simpler terms, PAR measures the effectiveness of the light concentration. When upgrading your grow tent to use LED lighting, it’s PAR ratings you should be looking at above all else.How to measure PAR To measure the PAR of your current set up with HID lights, you’ll need to get your hands on a light meter. They’re usually pretty cheap but are a helpful little tool to have. You’ll then need to switch on your HID lighting and wait till they are fully warmed up before you can get a true PAR rating. Once they’re warmed up, use the light meter probe in the center of your grow space to get the PPDF reading – Photosynthetic Photo Flux Density. To get the best, most accurate results, you might want to temporarily move your plants from the grow area. Unlike HID lighting, which can often be used at a variety of different heights, in order for your LED to provide the correct PAR, the light needs to be placed at the perfect height. Without this, your plants won’t grow. The average height used for an LED light is 24-30 over plants, so you need to find the correct PPDF based on this measurement. Why use PAR? Using PAR to help you find the perfect LED replacement is highly accurate. Rather than messing around with wattage and lumens, measuring the PPDF of your current set up will provide you with all the information you need to find the right LED. Why use LEDs? As we mentioned previously, LEDs can offer much more light, while consuming much less energy – meaning LEDs are a more energy efficient option for the conscious grower. With an LED – that has the same PPDF as your HID lights – you'll be on your way to bigger and better yields, without the high energy costs. To find out more about how LEDs can benefit your grow tent, check out our other guide here.