Power usage

[Cammys]

While i enjoy playing with my trainset i am trying to find out how much the power it uses will add to my electricity bill i cant find any info on this subject things like running time and speed will contribute to this as more power would be getting used anybody able to help with this question thanks

[Chrissaf]

Your average modern DC locomotive if run at sedate speed will draw about 0.25 amps at 8 volts. This equates to 2 watts per hour [0.25 x 8] assuming that there are no loco being stationary periods.

Electricity prices are calculated in Kilowatts per hour. Subject to your supplier and tariff a finger in the air tariff say 15 pence per KWH.

So on this example you would have to run your loco continuously for 500 hours to cost 15p

Some power will be lost in the power supply itself which of course has a cost associated with it that will add to the 15p total, but this is unlikely to be significant.

[Howbi]

My calculation goes like this..........Average loco at medium speed consumes about 250 milliamps. @230 volts supply this equals 58 watts. If your electricity is priced at 16 pence per Kwh then your running cost will be 0.928 pence per hour. Maybe someone could check and confirm these figures. thinking_face.........HB

[Chrissaf]

Howbi,

You cannot mix the DC output of 250mA with the 230 volts mains input in your calculations.

The way that a power supply works means that the mains input current will be a proportion of the DC output current.

For the sake of simple arithmetic let's assume that there are no power losses in the power path and the mains input power is equal to the track output power.

Let's assume also that the locomotive consumption 250mA is at 8 volts DC as per my example above. This equates to 2 watts as I previously stated.

The input power must therefore also equal 2 watts if we ignore power losses in the power supply.

If the input voltage is 230 volts, then the input current has to be approximately 2 watts divided by 230 volts = 0.0087 amps = 8.7mA excluding power supply current consumption losses.

[Howbi]

Thanks Chris, I was unsure whether there was any power consumed by the power pack in reducing the voltage down to 12v to the controller.........HB

[Chrissaf]

Of course, in reality power packs run warm and heat is power. Thus some wattage is lost in the power supply, so the 8.7mA figure will be higher but not 100's of mA.

Modern 'switch mode' power supplies are very efficient so their losses will be less than traditional transformer based power supplies.

If you look at some typical power supply labels, you will usually find that the maximum rated primary mains input voltage side current is always specified at a current rating value that is less than the output side current.

[Gordonvale]

Before becoming engrossed in how much power a layout uses, have a go at working out how much power is used by the lights, heaters, fans etc in the room.

May I suggest the former will be of little significance compared to the latter.