**Calculating Power Consumption**

**Calculating Power Consumption of a LEDstreetLight
**

**
**The

**LEDstreetLight**energy consumption and cost calculation is simple yet confusing when you have to consider such things as power factor correction, ballast factor and efficiency of typical power conversion devices used in today’s street lighting.

In light of this, how do you determine power consumption of electrical equipment of a street light?

Let's understand the basics before we look at the mathematics involved!

**Electrical Calculation**

The basic unit of measure for electric power is the watt. Since the number of watts measured over a period of time (by hours) can accumulate into the tens of thousands, **energy consumption**
is measured in kilowatt-hours - one kilowatt (1kW) is equal to 1,000
watts. For one kilowatt-hour (kWh) of electrical energy to be consumed
then one kilowatt of electricity must have been flowing for one hour
(or, two kilowatts of electricity flowing for one half hour).

For example, a 1,000-watt light bulb turned on for one hour consumes 1kWh of electricity; ten 100-watt light bulbs turned on for one hour would also consume 1kWh of electricity. The cost of energy consumption use is equal to the total kWh consumed over a period of time multiplied by the local energy rate, expressed as cents or dollars per kWh ($/kWh).

**Approximating Energy Consumption**

To approximate energy consumption for your electrical equipment or
street light, you must determine the total wattage. You can do this by reading
the labels of all components, such as the ballast, or the
LED supply used in the street light. The wattage will most likely be stamped on
the nameplate of each of these components. In some cases, the wattage
requirements may not be shown on these components -- only amps and
volts. The amp requirement is usually stamped on the nameplate of the
component. You approximate the wattage simply by multiplying the amps
by the volts. However, to determine exact wattage you need to multiply
amps by the volts and by the power factor. If power factor is not
marked on the product label then you need to review the data sheet or
call the manufacturer.

Add up all the wattage of these components, then divide the total
wattage by 1,000 to obtain the kilowatts. Multiply this by the number
of hours the equipment is in operation and then by the energy cost rate
per kWh in your area. To help you determine the energy cost rate in
your area just look at your last power bill from your power service
provider This will give you the operating cost.

In short, the cost of operation per month will equal total watts
being drawn by the equipment divided by 1,000, times the hours used per
month times the cost per kWh.

All ballasts actually consume energy within themselves while
driving lamps. So, the total energy (watts) being drawn from the line
is the total of the energy consumed by the ballast plus the energy used
by the fluorescent or HID lamp. This additional energy consumption can
range from 1 percent to 25 percent of the total kWh. Solid-state
electronic ballasts consume minimal additional energy to energize the
ballast, whereas older magnetic ballasts may require up to 25 percent
additional energy to energize the ballast. LED
supplies also fall into the same category unless provided with power
factor correction circuitry. Since incandescent bulbs do not require a
ballast no additional energy is needed to drive the bulbs. For details,
always consult the manufacturer’s specifications to determine input
requirements for these components.

**Lighting Formulas**

Incandescent Lighting: Watts* X hours per day = watt-hours per day; X
days per year = watt-hours per year; ÷ 1,000 = kWh per year; X energy
cost per kWh = total annual energy cost.

Fluorescent and HID Lighting: Watts* X hours per day = watt-hours per
day; X days per year = watt-hours per year; ÷ 1,000 = kWh per year.
Total kWh per year X energy cost per kWh = total annual energy cost.

* Total wattage for all energy consuming devices in a sign

Here are some examples on how to calculate per-year energy-use costs for a medium size sign:

For Example :

Assumptions--A street light built with eight fluorescent 40-watt lamps remains
on for 10 hours a night, 365 days per year, and the energy use cost per
kWh is 19 cents.

The calculation--8 lamps X 40 watts each = 320 watts; divided by
1,000 = 0.32 kilowatts; multiplied by 10 hours = 3.2 kWh; multiplied by
$0.19 = $0.61 per night; multiplied by 365 days = $221.92 per year. If
the street light ballast were the magnetic type, then the per-year cost = 3.2 X
365 X 1.15 X 0.19 = $255.21

**Plug-in Solution**

**
**If
all else fails and you don’t know the full extent of the internal
lighting / power consumable configuration, use a ‘plug in’ solution.
There are several makes and models on the market. With most you need to
be a rocket scientist to operate it!

We have found the Power-Mate model :PM10A to be a great device for
easily and quickly calculating power usage and cost over time. The unit
is produced by CCI Pty Ltd.

Find out more about this device

You can use the device for any appliance working off a 240v 10amp power supply.