dt@yenta.alb.nm.us (David B. Thomas) (07/22/90)
I was wondering what my instantaneous electricity usage was, so I went outside and watched my meter. The little disc inside spun around once in 60 seconds, pretty much exactly. What does this mean? None of the other dials moved that I could tell. How much energy is indicated by one 'spin'? David
larry@kitty.UUCP (Larry Lippman) (07/23/90)
In article <1676@yenta.alb.nm.us>, dt@yenta.alb.nm.us (David B. Thomas) writes: > I was wondering what my instantaneous electricity usage was, so I went > outside and watched my meter. The little disc inside spun around once > in 60 seconds, pretty much exactly. What does this mean? None of the > other dials moved that I could tell. How much energy is indicated by > one 'spin'? The rotor of a conventional watthour meter is rotated by torque caused by electromagnetic forces. This torque is proportional to the instantaneous power in watts (volts * amperes * power factor). The speed of the rotor in RPM is therefore proportional to instantaneous power in watts. Two coils in the watthour meter (a potential coil and a current coil) produce an interacting magnetic field which in effect causes the torque to be the product of volts, amperes and power factor. A retarding force is also placed on the rotor through the effect of two permanent magnets. Watthour meters have a "watthour constant" (Kh), which is the number of watthours represented by one revolution of the rotor disk. There are also other constants which describe the number of revolutions of the rotor disk for one revolution of the least significant register digit. There is also a specification for rotor speed in RPM at a test rating. In practice, there are various meter vendors and designs which result in different watthour constants; this information may or may not be stamped on the face of your meter. As a general rule the following formula should apply: INSTANTANEOUS WATTS = (DISK RPM) * (WATTHOUR CONSTANT) * 60 Common watthour constants for 100 and 200 ampere single-phase 3-wire watthour meters are 3.6 and 7.2, respectively, but THIS DOES NOT APPLY TO ALL WATTHOUR METERS. Using the above formula, if you had a 100 ampere service with a watthour constant of 3.6, and the rotor disk moved at the speed of 1.0 RPM, your instantaneous load in watts would be 1 * 3.6 * 60 = 216 watts. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" {boulder||decvax||rutgers||watmath}!acsu.buffalo.edu!kitty!larry VOICE: 716/688-1231 || FAX: 716/741-9635 {utzoo||uunet}!/ \aerion!larry
bill@videovax.tv.tek.com (William K. McFadden) (07/24/90)
The meter on my house has markings on the disc that indicate how much energy
corresponds to one revolution. I don't know if they're all this way, but that
would be a good place to start.
BTW, 1 rpm sounds pretty slow; the meter on my house often looks like a 78 RPM
record spinning in there!
--
Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077
bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
Phone: (503) 627-6920 "The biggest difference between developing a missle
component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TIlarry@kitty.UUCP (Larry Lippman) (07/24/90)
In article <5921@videovax.tv.tek.com>, bill@videovax.tv.tek.com (William K. McFadden) writes: > The meter on my house has markings on the disc that indicate how much energy > corresponds to one revolution. I don't know if they're all this way, but that > would be a good place to start. > > BTW, 1 rpm sounds pretty slow; the meter on my house often looks like a 78 RPM > record spinning in there! If you had a 100 ampere service and your meter had a Kh of 3.6 (see my recent article) and you pay $ 0.10 per KWH, each revolution is about 1/28 of a cent. 78 rpm indicates an instantaneous load of about 16.8 KW, so at that rate you'd be paying the utility $ 1.68 per hour. Them rpm's add up fast! :-) Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" {boulder||decvax||rutgers||watmath}!acsu.buffalo.edu!kitty!larry VOICE: 716/688-1231 || FAX: 716/741-9635 {utzoo||uunet}!/ \aerion!larry
andyp@treehouse.UUCP (Andy Peterman) (07/24/90)
In article <5921@videovax.tv.tek.com> bill@videovax.tv.tek.com (William K. McFadden) writes: >The meter on my house has markings on the disc that indicate how much energy >corresponds to one revolution. I don't know if they're all this way, but that >would be a good place to start. > >BTW, 1 rpm sounds pretty slow; the meter on my house often looks like a 78 RPM >record spinning in there! Hmmm, sounds like a heat pump at work!!!
bill@videovax.tv.tek.com (William K. McFadden) (07/25/90)
In article <3877@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: > If you had a 100 ampere service and your meter had a Kh of 3.6 (see >my recent article) and you pay $ 0.10 per KWH, each revolution is about >1/28 of a cent. > 78 rpm indicates an instantaneous load of about 16.8 KW, so at that >rate you'd be paying the utility $ 1.68 per hour. Them rpm's add up >fast! :-) Actually, our power is about $0.035 per KWH up to 300 KWH and $0.043 above that, so your figures are about two times too high. (Out of curiousity, is there anyone with cheaper power?) Also, 78 RPM is a slight exaggeration. It seems like it's going that fast, but I don't think it really is. Also, the average rate is probably a lot lower than this. For some reason, I seem to look at the meter when the dryer, water heater (no flames--I rent), oven, and air conditioner are running. :-) The water heater, dryer, and air conditioner use 4.5, 5.2, and 1.6 KW, respectively. I don't know what the oven uses. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill Phone: (503) 627-6920 "The biggest difference between developing a missle component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI
larry@kitty.UUCP (Larry Lippman) (07/26/90)
In article <5928@videovax.tv.tek.com>, bill@videovax.tv.tek.com (William K. McFadden) writes: > > If you had a 100 ampere service and your meter had a Kh of 3.6 (see > >my recent article) and you pay $ 0.10 per KWH, each revolution is about > >1/28 of a cent. > > Actually, our power is about $0.035 per KWH up to 300 KWH and $0.043 above > that, so your figures are about two times too high. (Out of curiousity, is > there anyone with cheaper power?) You don't know how lucky you are. How about this, as taken from a recent New York State Electric and Gas Corp. bill? First 350 kwh @ $ 0.118618 Next 670 kwh @ $ 0.105216 While NYSEG did deduct $ 0.007314 per kwh as a "fuel adjustment" credit, this can also turn into a debit. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
whit@milton.u.washington.edu (John Whitmore) (07/27/90)
In article <3888@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <5928@videovax.tv.tek.com>, bill@videovax.tv.tek.com (William K. McFadden) writes: >> >> Actually, our power is about $0.035 per KWH up to 300 KWH and $0.043 above >> that, so your figures are about two times too high. > > You don't know how lucky you are. How about this, as taken from a >recent New York State Electric and Gas Corp. bill? > > First 350 kwh @ $ 0.118618 > Next 670 kwh @ $ 0.105216 > Thanks in part to the Columbia river's many prime hydroelectric dam sites, in Seattle, our bills come out like: First 290 kwh @ .0207 Next 564 kwh @ .0333 * amounts billed include state utility tax at the rate of 3.852 and Seattle occupation tax at the rate of 6.600 So, the local utility is charging about nine-tenths of the above amount for electricity (and the anti-business and occupation tax soaks up most of the tithe). Rates vary seasonally; during heating season, the rate topped out at .0503 (presumably, dollars per kilowatt-hour). John Whitmore
dak@sq.sq.com (David A Keldsen) (07/28/90)
larry@kitty.UUCP (Larry Lippman) writes: >In article <5928@videovax.tv.tek.com>, bill@videovax.tv.tek.com (William K. McFadden) writes: [...] >> >> Actually, our power is about $0.035 per KWH up to 300 KWH and $0.043 above >> that, so your figures are about two times too high. (Out of curiousity, is >> there anyone with cheaper power?) > You don't know how lucky you are. Hmph. Don't bet on it. Oregonians sure enjoy that cheap power...paid for by the most-of-the-year rainy season, as most of the power is hydroelectric. (sigh. I even miss the rain...) >How about this, as taken from a >recent New York State Electric and Gas Corp. bill? > First 350 kwh @ $ 0.118618 > Next 670 kwh @ $ 0.105216 New York City and San Diego, are, as I recall, the two most expensive places in the continental U.S. w.r.t electric power. In 1986, San Diego was 11.3 cents per kwh. (Toronto is about 10.3 cents Canadian per kwh, at least on my current bill). > While NYSEG did deduct $ 0.007314 per kwh as a "fuel adjustment" >credit, this can also turn into a debit. Anyhow, this is straying a bit from the topic. Is there any place with cheaper electric bills than Oregon? -- // David A. 'Dak' Keldsen: dak@sq.com or utai[.toronto.edu]!sq!dak // "I have heard the mermaids singing, each to each." -- T.S.Eliot
brian@ucsd.Edu (Brian Kantor) (07/28/90)
Current San Diego residential electric rates are 2 - 241 kwh $.08148 (2 kwh/day minimum) 241+ $.12535 plus 1.9% franchise fee, plus $.0002/kwh surcharge tax, plus $.00012/kwh state regulatory fee. totalling: 2 - 241 kwh $.08335 241+ $.12805 SDGE claims that the typical residential bill runs around 350 kwh/month, as I recall. I use around 330 - mostly because of an old refrigerator, I suspect. - Brian