calculating energy usage

I'm pretty sure there's some wattage used by the ballast and that the bulb wattage is just that the watts used by the bulb not the fixture. I'm sure someone smarter than me could either confrim this or tell me I'm wrong. If your really intrested in true power usage there is a power usage meter that can be bought pretty cheap $20 -$30 bucks http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU
it will give you the actual cost of running just about anything.

Pumps rarely run at their stated wattage.
I found a wide variation in usage from different MH ballast in the past. Electronic seemed within reason but a 400w magnetic ballast could be using 475W.

I used the kill-o-watt meter on some things around the house last year. Couple of box fans we where running used 125w each. Considering they were on all the time it may have been better to run the AC for an hour or so. lol

Ok, I already ordered that device from Amazon. I love measuring stuff!

Let me rephrase my question:

I understand that there are going to be variances between actual power used and a devices rating. Also, I can see that a lighting fixture that uses an x watt bulb will actually consume (x - y where y = ballast/resistance/heat loss/other power drains) in reality.

However, would it be safe to say that in theory a 50 watt incandescent would use the same as a 50 watt T5, which would use the same as a 50 watt T5HO or a 50 watt MH?

Given that each fixture has it's own level of efficiency and overhead, would you expect them to all be in the same ballpark? It seems that they would all be expected to measure quite closely to each other in actual electrical use.

ballpark yes but incandescents have no ballast. even ballasts can very in there draw the electronic ones are more efficient then the regular ones and leds claim very low wattage but you need a transformer and a driver to run them

This should be interesting. I'm looking forward to getting that device and measuring everything I can think of!

Dave-H said:

This should be interesting. I'm looking forward to getting that device and measuring everything I can think of!

Click to expand...

it's the best way amprobes and math are a pita and don't account for Fluctuations in wattage

One place to start is to know how much energy the system is actually using. I have a KiloWatt meter plugged inline. The meter tells me how many watts the system use on average over a day. It's really handy!

I just went through this with my wife. She was questioning what my new tank was going to cost us per month on the electric bill. I simply added all the rated wattages on everything I was going to run and then added an extra 50 watts as a buffer. Multiplied the total wattage of things that would run constantly then added total wattage of equipment that would be on a cycle and multiplied it by the 22c/KwH it costs here in the Philly area. Seems like you're looking for a slightly more precise measurement though. Im interested to see what you get out of that wattage meter. Could be something I'd invest in soon....

they make these http://energymonitor.com/Products.html to monitor whole house usage I've seen them cheeper but can't remenber where maybe ebay

I work for the local utility company and have done some work with Smart Grid Technology in our substations for our distribution system. Related to this, soon some of our customers will be able to monitor their energy consumption in their homes as part of a pilot program. Seeing how their seems to be a large push for clean energy and reducing the demand, being able to monitor your household usage will become the norm for many in the near future.

Monitoring the whole house seems useful, but to really reduce power consumption it seems like you want to assess each device/item individually. I am exited to get that thing!