A lot of time we are asked what is the equivalent LED product to convert from Metal Halide, High Pressure Sodium or Mercury Vapor. And a lot of time, we have a product in mind that works based on past experience. But how did we come up with that product, and how did we make the original decision on what was the proper replacement?

There’s a lot of science that goes into light, color, quality, and each light had it’s own characteristics. For example, it takes less LED to replace High Pressure Sodium than it takes to replace Metal Halide. And we are talking a lot more than just lumens. We are talking about color temperature, quality of light and something called photopic / scotopic lumens.

In the world of lighting, we measure foot candles with a light meter, this is called a photopic measurement. The light meter picks up everything, including spectrum’s that are invisible to us. Now, we humans see things to, and this is called scotopic lumens. Our rods and cones read and interpret light. And it does so differently than what a light meter does. So it is not uncommon when we demo a LED Light against a HPS light or Metal Halide, we first ask “Which is brighter” before we show the light meter reading. It leaves a few people scratching their heads. Well, that’s the science of of it all, and fortunately there is some handy tables called SP ratios that allow us to take the lumens of a particular light (photopic lumens) and multiply it by the S/P ratio to get the scotopic lumens equivalent.

For example, the S/P ratio for High Pressure Sodium is 0.40. The S/P ratio for LED at 5000K is 1.8. So if you take 40,000 lumens of HPS and multiply it 0.4, the effective scotopic lumens is 16,000. To get the same amount of lumens from LED, take the 16,000 and divide it by the S/P ratio and you get 8888 lumens. So the 8888 lumens of LED is the photopic measurement, the 16,000 LED lumens is the scotopic lumens measurement. So in an nutshell, you need 8,888 lumens of LED to replace 40,000 lumens of HPS from a scotopic point of view.

Here is a handy chart of common lights and ratios for you to use.

Improving your home energy efficiency is a worthy and admirable goal. You can help reduce your impact on the environment while saving money with savvy decision making. However, the up-front investment for some efficiency upgrades is substantial, so always do your due diligence before you find electrician services and commit to buy. Read on to clear up some misconceptions about home efficiency and make sure your money is being put to good use.

You Don't Have to Sacrifice Your Comfort: It's true that the best way to conserve energy is to use less of it with strategies like turning off the lights or keeping the temperature lower in the winter. But that doesn't mean you have to sit shivering in the dark. The key to efficiency is to get the same amount of utility for less energy input. That means replacing old incandescent bulbs with LED versions, or investing in better HVAC technology like a smart thermostat. That way, you can keep your home environment tuned to your comfort while reducing consumption at the same time.

Don't Rush into a Big Ticket Item: The most dramatic way you can upgrade your efficiency is with a brand new heating or cooling system. Equipment efficiency has improved drastically in recent years, and new technologies like geothermal heat pumps, biomass boilers and solar panels can all reduce your bills dramatically. However, they aren't risk free. You’ll often face a significant up-front investment when you find electrician services for these installations, and the actual savings that you will realize can vary widely based on factors like the price of fuel. You could also see a loss if you make a big purchase and decide to sell your home soon after; there’s no guarantee you’ll recoup the cost in the selling price.

That's not to say you should avoid large efficiency investments – just look before your leap. You will get the best return from these items if you already need to replace outdated equipment anyway, and if you plan to stay in your home for many years. To reduce some of the upfront costs, you can also look for federal tax credits that refund up to one third of what you spend, as well as options to lease solar panels so you don't have to put any money down at all.

Don't Forget the Insulation: On the other side of the coin, new HVAC technologies won't do you much good if all that treated air just leaks into the outdoors. One of the biggest ways you can improve your efficiency is by plugging leaks and upgrading your insulation, which is typically a much cheaper fix. With a leak detector, some caulk and spray foam insulation, you can seal up your house with minimal investment, saving you money in the short term as well as preparing the house to get greater efficiency out of newer technologies.

For more straight shooting about how to get the most value for your efficiency investments, find an electrician to conduct an energy audit on your house. Your local Mister Sparky® is always available to help!