Cost of using lights

[GG]

How much does it cost to run 2-175 watt light fixtures 300 hours a month at .12 cents a KW hour.

 

[480sparky]

I come up with $12.60.

 

[GG]

I come up with $12.60.

Thanks brother. You mind showing me the math, as I have an owner that has a tenant that wants to know how much the light bill is every month. Its an apartment complex and they stuck the 2 outside lights on the tenants panel. There is no house panel.

 

[480sparky]

2 x 175 x 300 / 1000 (k for kilowatts) * $0.12.

Now I gotta ask........ are these HID lights?

 

[dbuckley]

2 x 175W lamps is a load of 350W

Each hour you consume (350/1000) = 0.35KWh

You operate for 300 hours, so (300 hours * 0.35KWh) = 105KWh

You said ".12 cents a KW hour"; I bet you mean $0.12 or 12 cents per KWh.

So, A KWh costs $0.12, ($0.12 * 105 KWh) = $12.60

Ooh - I agree 480Sparky's numbers - thats cool!

And he beat me to it; must type faster

 

[GG]

are these HID lights?

Yes, they are mercury vapor bulbs.

 

[480sparky]

Yes, they are mercury vapor bulbs.

That may skew the math.

 

[kwired]

Yes, they are mercury vapor bulbs.

The lamps are 175 watts, the ballast will have some losses that are in addition to lamp wattage so total used will be more than that.

 

[norcal]

Yes, they are mercury vapor bulbs.

Are they the cheapie "dusk to dawn" yard lights? They are around 3.3A @ 120V.

 

[kwired]

Are they the cheapie "dusk to dawn" yard lights? They are around 3.3A @ 120V.

That will give you 396 VA, but you will also need to know power factor to be able to calculate watts.

 

[cowboyjwc]

Wow, on this forum, everyone answered the question just as the OP posted it and nobody chimed in that it was a code violation.

 

[GG]

Are they the cheapie "dusk to dawn" yard lights? They are around 3.3A @ 120V.

Those are them.

 

[GG]

Wow, on this forum, everyone answered the question just as the OP posted it and nobody chimed in that it was a code violation.

What code section requires a house panel?

 

[cowboyjwc]

What code section requires a house panel?

210.25.

Doesn't require a subpanel, but does say that the exterior lights "...shall not be supplied from equipment that supplies an individual dwelling unit."

 

[480sparky]

210.25.

Doesn't require a subpanel, but does say that the exterior lights "...shall not be supplied from equipment that supplies an individual dwelling unit."

Maybe the OPs wiring predates that requirement.

 

[cowboyjwc]

Maybe the OPs wiring predates that requirement.

Sounded like he was adding them, but you could be right, though that's never stopped anyone on here before.

 

[kwired]

Wow, on this forum, everyone answered the question just as the OP posted it and nobody chimed in that it was a code violation.

That was not what he was asking about, but I knew sooner or later someone would mention it

 

[GG]

I was not adding the lights, only replaced a broken photo cell on one of the 2 lights. The apartments are maybe 10 years old, max. How far back does 210.25 go?

 

[cowboyjwc]

I was not adding the lights, only replaced a broken photo cell on one of the 2 lights. The apartments are maybe 10 years old, max. How far back does 210.25 go?

If the building is 10 years old, I just looked in the 1996 NEC (just happened to have it handy) and 210.25 is there.

 

[480sparky]

If the building is 10 years old, I just looked in the 1996 NEC (just happened to have it handy) and 210.25 is there.

Who says they had adopted the '96 at the time? Maybe they were still on the '93, or the '90, or even the '87. Heck, there's no law that says you even have to adopt the NEC. It could have been some other standard, even a home-grown one.