Here’s the deal. I’ve just moved into a new appartment, and I have to pay my own power for the first time (all my other places it was included.) I also found out quite by accident that the outside light and the hall light for this building is on the power circuit with my new appartment. I’ve called the landlord, and he will have it changed (eventually…)
It got me wondering, if you have a light fixture that is turned on, but there is no lightbulb in it, does it consume power? Nope, I’m not gonna keep everyone in the dark, it just started me wondering. It seems to me that if it does, it would be very little, otherwise switching to a lower wattage bulb wouldn’t conserve electricity. But I know next to nothing about this sort of thing. Enlighten me?
No, an empty socket won’t consume any power. Neither would unused wall sockets or batteries just sitting on the table.
So yes, switching to a lower wattage bulb will definitely conserve energy. Switching to fluorescent lights (which have much lower wattage for comparable brightness incandescent bulbs) conserves even more energy.
scr4 is right on the money for regular residential incandescent bulbs.
An additional thing to be aware of is that the reported bulb lives of compact fluorescents aren’t neccesarily accurate for all uses. The published numbers assume 8 to 12 hours per start, which means most of the bulbs will last that long if you turn them on for 8 to 12 hours at a pop. If you used it for a shorter period, the life drops dramatically (reports vary but 40-60% decrease is typical), and considering how much CFBs cost compared to regular incandescent bulbs, it probably doesn’t make sense to get them for short term uses. They would be good for the outdoor lights or hall lights you mentioned though.
Also, high intensity discharge (HID) lights, like metal halide or mercury vapor, have ballasts which can consume significant amounts of energy with no functioning bulb in the fixture. Some places use these for outdoor security lighting, but it is unlikely.
I hate to do this, but if I was wondering if I could use this post to ask another (somewhat related) question: What does your typical power meter measure? Does it measure apparent power (V * I) or apparent power (V * I * cos(theta))?
Put another way: Let’s say I turn everything off in my house. Presumably, the platter/disc thing in the power meter will stop spinning because no power is being used. Then let’s say I hook up a bunch of large capacity / high voltage capacitors to an outlet. Current will then be flowing back and forth through the power meter, but no power will be used. Will the platter/disc thing in my power meter start to spin again? Or is it intelligent enough to know no power is being used?
Residentially they charge for energy, not power, but I know what you mean. Local utilities in So. Cal. charge on real (or “active”) energy, kiloWatt-hours, so it’s VxIxPF/1000 per unit time, where PF is Power Factor, or cos(theta). I believe in other parts of the country they charge for apparant kVAh, which would be just VxI/1000 per unit time.
You can tell by checking out the meter. If it says it reads kWh, it is “active”. If it says kVAh, it’s “apparant”.
Commercial and Industrial customer’s over a certain size (250 kW max 15 minute power draw) have meters for both kW and kWh, plus one for power factor.
In one of my apartments in New Orleans, one of my neighbors noticed that some of the exterior lights were on his meter. The landlord had it fixed as soon as the tenant started sending his electric bills to the landlord.
Are you paying for the electricity until it it fixed? If so, eventually may be a long time. If the landlord has to pay the bill eventually will come a lot sooner.
We fitted an induction fan to a large industrial boiler unit using a SMPS and we needed to work out the energy saving before deciding wether to do the same to the other five.
We used both types of meter KWh and KVAh from which we worked out the p.f easily enough.
In the end the investment was deemed to be pointless as the boiler plant was going to be run much less following installation of a gas turbine generator plus all the associated heat recovery plant.
P.F meters have high and low markers which the moving needle sets in place.If you exceed agreed limits you pay handsomely for it.Even a 15 minute excursion is very expensive as you get billed for that p.f reading for the whole of the metering period.You do get KWAh meters in the same premises too so the billing is pretty complex, involving average p.f, maximum agreed p.f, maximum demand, and energy used.You often also have to agree to take a minimum load too to get the tariff you want.
The upside is that by breaking the contract down like this can significantly reduce costs.
Our domestic supply meters are all KWh but then dwellings are not particularly reactive.
casdave - PF charges vary greatly depending on your utility. California utilities charge almost nothing ($0.25 per highest monthly kVAR is typical, which for large CI customers is rarely >1.5% of total bill ), but elsewhere I have heard it can be as much as 30% of your bill! Is that right? Couldn’t you just buy a big auto-capacitor, or is it not cost effective? What is an SMPS too? (I am assuming it’s a variable freq. drive)
Doc Matrix - people get screwed like that all the time. Everyone would be better off if the estimated the monthly cost of the lights and just gave a rent discount to the person whose meter the lights were on. The cost of rewiring and adding an additional meter will never be recovered. The worst one I ever saw was an electrician who wired 4 condos so that 3 of them split the 4th’s load. The electrician bought the 4th condo, and didn’t get a bill. Eventually a former lover turned him in and he got charged with fraud and theft, sued for $, lost his licence, and had to pay to have the place rewired, new meter installed, etc.
Gravity
That was a long time ago and it didn’t happen to me so I don’t know/remember all of the details.
This may not need to be said, but please, please, don’t just send your landlord the bill because I said so! Before you send your landlord your bills, talk to a lawyer or maybe the power company.
Engineer Don
Are you saying the tenant should work out a deal with the landlord for a discount instead of insisting that the wiring be fixed? That might be better for the tenant in the long run.
Well, I used to live in the apartment across the hall. The lights just mysteriously stopped working one day. Later I found out that that was the same day that the last tennant had their power shut off. They also came back on when we had the power turned on. Not nifty detective work, but handy that I had my eyes open at the right times.
Goodness, I wasn’t really going to send him the bill! I was going to modify the method, and ask him if I should send him the bill.
You were right about the SMPS - some folk get mixed up with the soft starter system.
In the UK we only had one utility to go to but it’s been split up.As you might imagine they originally had all sorts of ways to increase your bill.
You had to agree a maximum demand, which could easily be differant to your maximum possible consmption, you had to agree a maximum p.f deviation, etc etc.If you could comply with all these conditions the differance could be well over 30%, in fact we had managers who did not fully understant the complex system of tariffs and the result was that our small 30MW CHPS station was running at just about break-even for 18 years before we changed contracts following a change at the top and made profits of up to £1.5mill selling infill power back to grid.Our National Health Service can be very slow to shed the incompetant.
Tretiak
How do you find out it outside lights are on your bill?
Easy - turn everthing in your apartment off, if the meter still rotates/counts as something is still using.Check the consumption over a set period like a minute, just count the revolutions, and then turn a lamp on with a similar consumption - time the meter rate over a minute and it should be near double, if it is way out then it is either more than just that outside light or you picked a wrong light to sample against.
A single bulb that stays on 24x7 can cost $5.00/month or more depending on wattage and cost/kwh. It’s not that difficult to compute the power consumption if you’ve got these details.
Tretiak
How do you find out it outside lights are on your bill?
Or you could wait until the suspect light is operating and throw the main power breaker of your breaker/fuse box. If it goes off and on with that switch, it’s on your bill. NOTE: Turn you PC off before you do this. You’ll have to reset all of your clocks which don’t have a battery back up too.
It gets a lot messier if you throw in harmonics Real power as defined by VIcos(theta) only counts the 60 Hz power- it doesn’t include power from harmonics. This isn’t well measured by conventional meters. In fact, there’s not a lot of agreement on exactly HOW to measure it …
