Math check -

klmmicro

Well-Known Member
Trying to get the cost of everything clear to roommate. Our electric bill jumped about 6 months ago (had nothing running of mine) and the roommate blamed the garden. Tried to explain to him that there is no way that the garden is costing over $100 a month, but he insists. Tried to avail him with facts, but the figures are not making any sense to him. Here is how I arrived at my figure I gave him:

My garden consists of:
1x 600W digital HPS
1x aquarium air pump
2x 6" low consumption vent fans
1x 8" circulation fan

Total wattage is 650-680 watts for everything if it was all on at once. I am getting a Kil-O-Watt meter this afternoon and as everything runs off a single socket, I will be able to trend the entire systems consumption throughout the day. For now though, I use 660 watts as my figure.

Here goes the math -

660 watts per hour total, or .66 kWh. This is for everything (per 24 hour period); air pump (24 hours), lights (18 or 12 hours) and nute pump (1/2 hour).

For veg, the lights are on for 18 hours. This phase is at most 30 days.

.66 kWh for 540 hours per month = 356.4 kW per month. At $.12 a kW for 356.4 kW should equal $42.77 a month on the bill. Even at $.15 per kW the bill for the garden should be no more than $53.46/month.

For flowering, the cost for 30 days is:

.66 kWh for 360 hours per month = 238 kWh per month. At $.12 per kW for 238 kWh the cost should be $28.56 a month on the bill. Again, if the cost were $.15 a kW, the bill would be $35.70 a month.

Taking the higher of the two possible costs, one month at $53.46 and 3 months at $35.70 and the ENTIRE cost of electricity for a crop is only $160.56 from start to finish.

He is claiming that the jump in cost was about $110 per month...am I missing something, or did I mis-calculate what the cost should be? Any thoughts appreciated.
 

dew-b

Well-Known Member
Trying to get the cost of everything clear to roommate. Our electric bill jumped about 6 months ago (had nothing running of mine) and the roommate blamed the garden. Tried to explain to him that there is no way that the garden is costing over $100 a month, but he insists. Tried to avail him with facts, but the figures are not making any sense to him. Here is how I arrived at my figure I gave him:

My garden consists of:
1x 600W digital HPS
1x aquarium air pump
2x 6" low consumption vent fans
1x 8" circulation fan

Total wattage is 650-680 watts for everything if it was all on at once. I am getting a Kil-O-Watt meter this afternoon and as everything runs off a single socket, I will be able to trend the entire systems consumption throughout the day. For now though, I use 660 watts as my figure.

Here goes the math -

660 watts per hour total, or .66 kWh. This is for everything (per 24 hour period); air pump (24 hours), lights (18 or 12 hours) and nute pump (1/2 hour).

For veg, the lights are on for 18 hours. This phase is at most 30 days.

.66 kWh for 540 hours per month = 356.4 kW per month. At $.12 a kW for 356.4 kW should equal $42.77 a month on the bill. Even at $.15 per kW the bill for the garden should be no more than $53.46/month.

For flowering, the cost for 30 days is:

.66 kWh for 360 hours per month = 238 kWh per month. At $.12 per kW for 238 kWh the cost should be $28.56 a month on the bill. Again, if the cost were $.15 a kW, the bill would be $35.70 a month.

Taking the higher of the two possible costs, one month at $53.46 and 3 months at $35.70 and the ENTIRE cost of electricity for a crop is only $160.56 from start to finish.

He is claiming that the jump in cost was about $110 per month...am I missing something, or did I mis-calculate what the cost should be? Any thoughts appreciated.
can't tell you jump all over the place rember stoners have a short attion span . the only thing i can tell is you are using 600 watts every hour with your light . post the watts of every thing and the cost per kw you pay. rember keep it simple .
light 600w
fan ?watt(just put the watts of each fan)
air pump ?watt
itwill help to get a better accrat count of what you use.
it could be somthing other in the house like a water bed, washerdryer or a frezzer. put cfl lights in all the household lamps that will help to lower the bill. could even be a leak in water heater if its elecric not gass.
 

323cheezy

Well-Known Member
i have the same problem.....
my roomies want me too shut off my lights cause of the damn electric bill...
im about a month from harvest.... and theyre bitchin....
but when its there all gonna be asking for ganj....
so what exactly doesit cost for 12hrs of the 400hps a month????
 

klmmicro

Well-Known Member
Hehehe, you are right about the attention span...mine is short enough that I made it all a bit complex.

600 watt light
45 watts for fans
15 watts for air pump

660 watts for 18 hours
15 watts for 6 hours

Total kWh used in 24 hours: 12.24 (for veg).

We pay about $.12 per kWh. This means that the garden is costing $1.47 a day. In a 30 day month, that should come out to $44 during veg.

My concern is that we have something else in the house going bad.
 

angelsbandit

Well-Known Member
Don't know your power rates, but:

400 watts 12 hours per day is 144 KWH per month - at .15 per KWH your cost would be $21.60 per month.
 

klmmicro

Well-Known Member
Don't know your power rates, but:

400 watts 12 hours per day is 144 KWH per month - at .15 per KWH your cost would be $21.60 per month.
So the formula is:

Watts X time X .001 X 30 = kWh per month (400*12*.001*30=144).

Multiply kWh per month by kWh charges for the monthly cost, or:

144*$.15=$21.60 per month of operation.

This makes sense to me and is how I was calculation cost of operation.
 
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