How many Kilowatts does my treadmill use?

I own a fitness center and I'd like to understand how much my treadmills are costing to operate.

Each is 120 volts and 15 amps. Does this mean that each is consuming 1.725 Kw per hour and therefore 41.4 Kw per day (we're open 24 hours).

Or, is each consuming some nominal amount of power when not in use and then more when someone is using it.

Finally, if it consumes more power when someone is on it, does it consume more power the faster someone walks/runs and the more that person weighs (because the treadmill is "working harder" at higher speeds)?

Bonus points are give for helping me calculate an exact number if we assume the avg treadmill has a 180 pound person walking/running at 5 mph (out of 15 max) for an average of 5 hours a day :)

Thanks!!

Answer:
If you want to measure your own appliances, check out the Kill-a-Watt device at the link below. It is available online or at home improvement stores and Radio Shack. I've seen it for around $25 US.

You can plug it in and it will display the volts, amps, watts, VA, and power factor. If you leave the device plugged in, it will keep track of the cumuative kilowatt-hours over time. In one day you'll know exactly what the treadmill costs you.

If I have a chance, I'll stop by a sporting goods store and test a few treadmills with my Kill-a-Watt device before this question closes.


Since you own a business, you might be paying a "demand charge" in addition to an energy charge. If this is the case, then a treadmill is costing you more than just the kWh accumulated over the month.


While the device might display 15 amps on the nameplate, the NEC does not allow a corded device to draw more than 12 amps steady-state. There are some exceptions for microwave ovens, toasters, blow dryers and similar "short duration" appliances.

NEC Section 210-21(b)(2)
"A cord-and-plug connected load in excess of 12 amperes shall not be connected to a 15-ampere receptacle on a branch circuit supplying two or more receptacles."
W = V x A
W = 120 x 15
W = 1800 = 1.8 kW/hr

THis is the maximum rating for the treadmill. It is likely that it never runs anywhere near 15 amps, even when fully loaded. The 15 amps is most likely the breaker rating required for the treadmill. But, assuming that it runs at 1/3 power (5 vs 15 mph) for 5 hours per day, we can calculate your energy use:

1.8 kW/hr x (1/3) x (5 hours) = 3 kW/day
If you are open every day:
3kW/day x 365 days/year = 1095 kW/yr

An average electrical rate is about $0.10 per kWhr, so let's calculate your cost per year for each treadmill:

1095 x 0.10 = $109.50 per year

Kinda expensive, huh? Well, if you are open 24 hours per day, your lighting bill is most likely multiples of 10 higher than this.
You are correct in assuming that the rating plate that is telling you 120V / 15A isn't telling you the whole story. 15A is the maximum load that the device is allowed to draw, but the actual current will depend upon the speed and the load generated by the person using it.

A heavier person or one creating more resistance to the belt for any reason will increase the load, a lighter person will decrease it. Higher speeds will draw more current. Lower speeds the opposite.

Your gut was telling you the truth. There's no way of knowing what the "typical" load is for one of these things just by looking at the rating plate.

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OK -- just sitting idle, turned on, and with the motor NOT running, the device probably consumes VERY little current (perhaps 0.1A) -- enough to keep the display alive.

While running with someone actually using the equipment, if you estimate something on the order of 5A, that's probably more than adequate to cover the load of a typical person at the speed you specify.

You've done the right thing to come up with some kind of duty cycle (5 hours out of 24).

SWAG = 0.1A x 19 hrs = 1.9AH
SWAG = 5.0A x 5 hrs = 25AH

Round it all out to 27AH per day @ 120V and you get 3.24KWh in a typical day.

Again, these are all pretty wild swags. The manufacturer would have to be prodded into giving you idle and typical currents, or you'd need to hook up an ammeter and get those values yourself.
The only accurate way to determine how much power each treadmill is using is to measure the line current with an amp meter while it is in use. An inductive amp-probe clamps over a single wire and measures the amps flowing in that wire by magnetic induction. A "true rms" clamp-on ampmeter and a conductor separator are standard tools carried by most electricians. Also, measure your line voltage during equipment use. Take a few measurements with the machine(s) in use and you can do these calculations:

VA = measured amps * measured volts
If you assume a 0.8 power factor for your motor-like treadmill loads, then.
KW = (0.8) * (measured VA) / 1000

If your electric power utility contract includes a "demand factor" charge then your actual electrical bill will be higher than just the KWhrs * rate, based on your peak "demand load" during the billing month. The highest peak demand in that period determines a factor that is applied to the measured electrical use and you are billed a surcharge for that "demand load". This usually only applies to commercial utility accounts.
The DC motors for treadmills are rated at between 2 and 3 horsepower. Your "professional" high-end models will most likely have 2.5 or 3 horsepower motors, since they are rated at 120V 15 Amps.

Humans can generate a sustained 1/4 HP for 30 minutes, but most of the 2.5 HP is used to overcome the friction of the belt over the running surface. Figure, when the treadmills are 'on' that they use up most of that 2.5 HP.

You also need to account for the conversion efficiency of the DC power supply and the (in)efficiency of the motor (both in the high 90% range). 2.37 HP with 95% efficiency represents 15 Amps at120 VAC, so most likely you are really using most of those rated 15 Amps.

When people run faster the treadmill does indeed, use more power. The numbers above would represent the fastest possible speed, at the greatest incline, with a >250 lb person running.

As a pure educated estimate... 180 lb (2/3 max weight), at 5 mph (1/3 max speed), that would be approximately 6 Amps, which is 720 Watts, and for 5 hours that's 3600 Watt-hours. It could range anywhere from 3000 to 4000 Watt-hours.

With power costing 10 cents/kW-hr (a basic average across the US), that's only 40 cents to operate.
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If you are really interested in the individual power consumption you can perform some experiments utilizing the electrical meter and a stopwatch. When you go to the meter you will see a disc moving around and around. On the face of the meter look for a marking such as Kh6. This is known as the meter constant. The meter constant allows you to calculate the power in watts being used at any time. The Power is found by:

P(watts) = (r/min.) x 60 x Kh

r/min. = the number of rotations of the plate in one minute
60 = the number of minutes in one hour
Kh = the meter constant
P(watts) = (the number of rotations of the plate in one minute) x (minutes in one hour) x (meter constant)

For example, if you counted two revolutions of the plate in one minute, and the meter constant was 6, then the power reading would be:
P(watts) = 2 x 60 x 6 = 720 W


You can do this with no treadmills running and only the AC and lights. This will give you a baseline since they will be going along with the treadmills. Then with treadmills going you can do it and deduct the AC and lights from it yielding the treadmills.

Things fluxuate too, so you may want to do a longer test. Check how many treadmills are going. Get your watch and go to the meter and start counting revolutions.
Then subtract out the lights and AC which were measured previously and you have it.

Now you can read the meter befor you leave at night and again in the morning when you come in write down the meter reading and the times. Subtract the night reading from the morning reading and you have the nights power consumption. The meter usually reads kW and you compute the hours. Multiply them together and you know how much power ($) you used that night. Do this every day and plot it in excel and you can graph your usage.

It takes a little time but it is important in determining where your hard earned money is going especially with the energy cost today.

Another good thing is that every time that disc turns it measures the actual energy NOT an estimate. And there are no power factors this is actual power consumed by all of your equipment.

After you conduct this analysis you will be quite knowledgeable and will defiantly identify where you can save money.

The answers post by the user, for information only, FunQA.com does not guarantee the right.



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