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<div><br></div><div><br></div><div><br></div><div><br></div><div id="composer_signature"><div style="font-size:85%;color:#575757">Sent from my Verizon Wireless 4G LTE smartphone</div></div><br><br>-------- Original message --------<br>From: greenbuilding-request@lists.bioenergylists.org <br>Date: 04/10/2016 2:00 PM (GMT-05:00) <br>To: greenbuilding@lists.bioenergylists.org <br>Subject: Greenbuilding Digest, Vol 68, Issue 7 <br><br><div>> How long would it take this $21.57 R10 water heater blanket to pay for itself with electricity at $0.15 per kilowatt hour?<br dir="auto"></div><div><br></div><div>With no blanket, 2070 Btu/day = 24h(135-67.5)G, which makes G = 1.28 Btu/h-F = A/Rv, so Rv = 14.6sqft/1.28 = R11.42. Adding the R10 blanket makes Rv = R21.42 with a 1104 Btu daily heat loss.</div><div><br></div><div>The difference is 974 BTU (0.28 kWh) per day worth 0.28x0.15 = $0.0426, so the pay back is $21.57 divided by 0.0426 = 506 days, ie 1.39 years.</div><div><br></div><div>Nick </div></body></html>