Sheesh-sorry for the formatting in the last email guys (fixed it so it's easier to read below) and hoping it doesn't happen again with this email...anyway: Found the link I was talking about; from http://www.generatorguide.net/watt-acpower.html In some regions utilities already installed digital power meters ("smart meters") at the residential level, which compute W, VAR, and PF. They may surcharge you for VAR. However, so far most US residential meters are still rotating-disc devices that measure only real watts, so PF of your appliances does not affect your cost of electricity. In these applications using power factor correcting (PFC) devices will not reduce your electric bills...Also, lower PF will cause larger current in utility lines and additional voltage drop in the wiring. In an extreme case, reduced voltage in the electrical system can cause overheating and premature failure of motors and other inductive equipment. Unlike residential customers, for commercial and industrial electrical customers, an electric utility company may assess a penalty for low power factor and collect additional charge when PF drops below 0.95. (And the important point from that)**Nevertheless, PF of the appliances should be taken into account when sizing a backup energy system, such as a home generator or an UPS** Which I think is a very important point no? Though checking into it, I can see that the high-end PCP&C PS have a PF of .98 http://www.pcpower.com/downloads/turbo_cool_specs1200_b_3835.pdf so I assume that's a non-issue for most desktops... The next interesting thing is the efficiency rating (which is 83% in the case of the Turbo Cool 1200) and how the manufacturer doesn't tell you what temp and load that's at...as the main criticism I've heard of 80 PLUS is that the medal ratings system is only done at room temp of 20C and that since temps will obviously go up as the unit is running, and go up a lot in the case of bigger PS with more stuff on them (as well as the ambient temp in the system) the efficiency will definitely go down, and thus lots of 80 PLUS certified PS might not even meet their current certification level...and of course efficiency varies with load too, though that seems to be pretty minor (a few %). Just some interesting things about power to keep in mind I hadn't really understood before! ;)
> From: [email protected] > To: [email protected] > Date: Mon, 1 Aug 2011 10:12:30 -0700 > Subject: Re: [H] PFC (power factor corrected) PS for PCs? > Well the confusion is that the utility *could* charge you for VA instead of watts, but apparently they don't for residential customers (since most residences only have older-style meters that read only watts) but they definitely do charge industrial customers for VA since they probably would have low PF otherwise...ahh, from the PF wikipedia article:-Importance of power factor in distribution systems-The significance of power factor lies in the fact that utility companies supply customers with volt-amperes, but bill them for watts. Power factors below 1.0 require a utility to generate more than the minimum volt-amperes necessary to supply the real power (watts). This increases generation and transmission costs. For example, if the load power factor were as low as 0.7, the apparent power would be 1.4 times the real power used by the load. Line current in the circuit would also be 1.4 times the current required at 1.0 power factor, so the losses in the circuit would be doubled (since they are proportional to the square of the current). Alternatively all components of the system such as generators, conductors, transformers, and switchgear would be increased in size (and cost) to carry the extra current.-Utilities typically charge additional costs to customers who have a power factor below some limit, which is typically 0.9 to 0.95. Engineers are often interested in the power factor of a load as one of the factors that affect the efficiency of power transmission.-And I read somewhere (can't find the link now; it was one of like 30 I was reading yesterday before I read this one that clearly states that utilities charge for watts, not VA ) that some utilities are installing meters than can read VA instead, since they have to pay to push VA and not watts...which actually makes sense to me.- BINO- > Date: Mon, 1 Aug 2011 05:55:00 -0400 > > From: [email protected] > > To: [email protected] > > Subject: Re: [H] PFC (power factor corrected) PS for PCs? > > > > What's the confusion? You're paying for watts....you don't pay for > > VA..that's a unit used for complex power, part if which includes > > reactive power, which is not converted to useful work. Real power is, > > which is measured in watts. > > > > On 8/1/2011 5:29 AM, Bino Gopal wrote: > > > Lol that's exactly one of the links I found (among about the 20 or so > > > I've been perusing all day), but it still isn't clear to me from any of > > > them whether I'm paying for VA or watts...anyone know for sure or does it > > > depend on your particular power company and the kind of meters they use > > > maybe...? > > > > Date: Mon, 1 Aug 2011 00:12:50 -0700 > > >> From: [email protected] > > >> To: [email protected] > > >> Subject: Re: [H] PFC (power factor corrected) PS for PCs? > > >> > > >> "Capacitor Input supplies have the characteristic that the Watt rating > > >> is in > > >> the range of .55 to .75 times the VA rating (power factor of 0.55 to > > >> 0.75)." > > >> > > >> http://www.power-solutions.com/watts-va.php > > >> On Jul 31, 2011 11:50 PM, "Bino Gopal"<[email protected]> wrote: > > > >
