<font face="arial" size="4"><p style="margin:0;padding:0;">excellent replies to yes, a complicated issue. i think i finally understand this. thank you kent and dan!</p>
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<p style="margin:0;padding:0;">todd</p>
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<p style="margin:0;padding:0;">On Monday, May 7, 2012 9:02pm, "Exeltech" <exeltech@yahoo.com> said:<br /><br /></p>
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<td style="font: inherit;" valign="top">Hello Todd,<br /><br />The short answer to your "is this a concern?" query, is "no".<br /><br />Reactive power is one of the more complex aspects of electric power, and<br />certainly one of the most misunderstood. It can and does involve inductive<br />loads (e.g. motors), capacitive loads (e.g. some types of power supplies),<br />and non-linear loads (e.g. switch-mode power supplies, dimmers, etc.).<br /><br />You likely know (or should know) "power factor" is the ratio of real power to<br />reactive power consumed by a load. Grid-tie inverters generate "real" watts,<br />which are then coupled to the grid. When a reactive load in your home is<br />consuming power, and you provide real watts to the load from the inverter,<br />this changes the ratio of real to apparent power consumed by the load as<br />seen by the utility company.<br /><br />Dividing real power by apparent power results in a unit-less value between 0<br />and 1 that describes this ratio.<br /><br />Let's say a load in your home is consuming 1,200 real watts, and 1,250<br />apparent watts. This results in a power factor of 1200/1250, which equals<br />0.96. Pretty darn good.<br /><br />Next, your grid-tie inverter provides 1,000 real watts back to the utility company,<br />which in turn is 1,000 real watts that the utility company no longer needs to<br />provide to the load described above. Thus the net "real" power consumed as<br />seen by the utility is now 1,200W - 1,000W = 200W.<br /><br />This means they sell only 200 watts to power your load, but the "apparent"<br />power aspect is still there.<br /><br />End result?<br /><br />200 real watts / 1250 apparent watts yields a power factor of 0.160. Terrible by<br />any power company standards, yet you've removed 1,000 watts from the grid.<br />This is the value that will be displayed on your meter.<br /><br />Efforts are underway by EPRI and others to help create standards for future<br />generations of grid-tied inverters capable of generating "reactive" power (where<br />volts and amps are out of phase with each other) to help mitigate this effect.<br />I'm a member of the committee working toward that goal. (No, we're not there<br />yet. It'll take time.)<br /><br />This is a very difficult topic to discuss and explain. Hopefully this helped.<br /><br />Like Tom Cruise said at the end of "Top Gun" .. "It's complicated."<br /><br /><br />Dan<br /><br /><br /><br />--- On <strong>Mon, 5/7/12, toddcory@finestplanet.com <em><toddcory@finestplanet.com></em></strong> wrote:<br />
<blockquote style="border-left: 2px solid #1010ff; margin-left: 5px; padding-left: 5px;"><br />From: toddcory@finestplanet.com <toddcory@finestplanet.com><br />Subject: [RE-wrenches] power factor<br />To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br />Date: Monday, May 7, 2012, 9:46 PM<br /><br />
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<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">wrenches,</blockquote>
<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;"><br /></blockquote>
<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">i have a question about my home's system. i was one of the first net metered systems in our area, so the utility company installed a fancy dual register meter which also displays kvar/power factor.</blockquote>
<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;"><br /></blockquote>
<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">when selling 1 kW today the power factor was .40 and the kvar was 2.37.</blockquote>
<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;"><br /></blockquote>
<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">this sounds horrible. <span style="font-size: 14pt;">question: is this a concern?</span></blockquote>
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<blockquote class="yiv955400255gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;">todd</blockquote>
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