Lighting systems have gotten vastly more efficient in the last decade. This is thanks to better bulbs, better luminaires and controls, and better lighting design – and let’s all keep working hard to make them even more efficient as technologies and design methods continue to improve. But, let’s also give ourselves a little credit for the great progress that’s already been made. For example, we’re now designing office lighting using one-sixth of the electricity typically used just 25 years ago. Imagine if we had made the same kind of progress with automobiles.
Stop reading for a minute and ask yourself: how much energy do you think you use driving to work, versus how much you use to light your personal share of your workplace? What is just the rough proportion you would guess? Let’s put some numbers to that:
Let’s say you drive a new car at the US average of 16 miles per day each way, and you average the current federal standard, 27.5 miles per gallon. That consumes a bit over a gallon of gas per day.
The same amount of fuel oil, burned in a typical power plant and distributed to your building through the grid, at an overall efficiency of 30%, will generate 14 kilowatt-hours. If you work in a 200-square-foot office and your workspace lighting power conforms to current ASHRAE standards, that gallon or so of gas will light your workspace for over 65 hours. Or, to put it another way, the fuel you use getting to work each day will light, for ten hours, not just your 200 square feet but actually 1,300 square feet – enough space for you and half a dozen friends.
How is that possible? Well, for one thing, when you stomp the accelerator on your base four-cylinder Accord (177 horsepower), in electrical terms your modest sedan is generating over 130,000 watts, and it’s doing it inefficiently. At that rate, it would take you less than 60 seconds to burn up enough fuel to light your workspace for ten hours.
Actually, our estimate is very conservative. If we get more realistic and factor in the inefficiency of refining and transporting gasoline, and we recognize that new buildings are required to have motion sensors to turn your lights off when you don’t need them, and we also recognize that the average American commuter vehicle doesn’t average anywhere close to 27.5 mpg (okay, and maybe your office is less than 200 square feet), we can come closer to a realistic answer to our initial question. And that answer is that if your workplace meets today’s lighting energy standard, your commute likely uses at least ten times as much fossil fuel as your workspace lighting each day.
So, how did you do on your guess?