120V vs. 240v - An essay by the blogmaster of TanningBeds.org

TanningBeds.org is a ad-free, non-profit website that answers questions posed by tanning bed owners in a no nonsense and unbiased manner. This essay is reprinted in full with their permission. The original article can be viewed here.

Dear Friends,

The biggest myth in the tanning industry is that beds that use 240V (or 230v, or 220v) are somehow "more efficient" or "use less power" than 120V tanning beds. I have answered this in the past, but was asked to retouch on the subject, and put the myth to rest. The "fact" that 240V is more efficient is usually told to a customer by an electrician or a friend who is an mechanic or some other self-proclaimed expert. As someone who began working with electronics before he had a driver's license, let me put it in plain English:

They are wrong. 240V is not more efficient than 120V for tanning beds.

Now, you can either believe me as someone who is experienced in these matters, or you can read on for a painfully detailed explanation of why and how they are wrong, and how (in general) a bed that uses 120V is actually more energy efficient than a bed that uses 230V.

I understand the confusion about efficiency, as there is a reason why people think this, but they are applying the wrong logic. There ARE cases where 240V is more efficient than 120V, but tanning beds isn't one of them. 240V is only more efficient when you are using polyphase 240V (like we have in the USA) and you are turning a MOTOR. Yes, something that spins round and round. Compressors, air conditioners and insanely large fan motors are good examples.

Motors that run on 120V have a single point in their rotation where they get a "bump" from the electricity, and have to make the rest of the journey using momentum. Motors that use polyphase 240V are designed to get this "bump" every 1/2 rotation (or 1/3 rotation for industrial equipment using three phase power), so they can spin faster, or spin the same using less electricity. (it's a Momentum/Physics thing, just trust me on this one.)

Tanning beds do not rotate around an armature. The fans they do have are just as efficient at 120V as 240V, and the fans only consume a tiny fraction of the total power used. In short, tanning beds are basically light fixtures that you lay down on. They are not spinning motors, and can not take advantage of the physics involved to conserve momentum.  They will operate just fine at 120V, 60V, 480V, as long as they get enough watts (watts = volts x amps) to strike an arc inside.

"So", you say, "Then why are you saying 120V is more efficient than 240V?". It is very simple. Most of the beds that use 220v to 240v use choke ballasts, which were designed about 100 years ago. They are a type of inductor and work reasonably well, except they are very inefficient and get very, very hot. Go ahead and grab one after it is been running an hour, I dare you. In the world of electronics, Heat = Wasted Electricity. Any heat that is generated by the electronics is electricity that wasn't used to make light, and was instead converted to waste heat. An inductor is a fancy way of saying "it is copper wire wrapped around an iron core in order to limit the amount of current that passes through". They are dirt cheap, reliable and inefficient.

Most 120V electronics are either magnetic (sorta efficient) electronic (some are efficient, some are not) or high frequency electronic (super efficient). The newer HF style ballasts can use up to 30% less electricity than choke/inductor ballasts, and up to 50% less than older electronic or magnetic ballasts. They operate just a couple of degrees above room temperature and produce only 1 to 3 watts of waste heat. All other power is converted into making the lamp work.

In a nutshell, the reason that 120V electronics are more efficient than 240V electronics has nothing to do with the voltage, only the age of the technology used inside the ballasts themselves. Most people mean well when they tell you that 240V is more efficient, but they are just simply wrong and don't fully understand. The next time someone tells yout that 240V tanning beds are more efficient, just smile. Better yet, point them to this webpage as a favor.

Dennis