<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">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 <b>Mon, 5/7/12, toddcory@finestplanet.com <i><toddcory@finestplanet.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); 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><div id="yiv955400255"><font face="arial" size="4"><div id="yiv955400255SafeStyles1336443436">
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<blockquote class="yiv955400255gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">wrenches,</blockquote>
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<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>
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<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>
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<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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