Hi OPERAHOUSE.......I replied to this thread a few weeks ago, but it appears to not have made it through, so I'll try again. I recently picked up one of these units as well, as of yet not yet installed. A couple of things from your initial post confuse me a bit.
1."the standby heat loss per day with no water usage is 3-4 KWH a day" "The HPWH consistently uses 800WH for a 12 hour period at night when no water is used" Would not the heat loss then be .8 KWH per day not 3-4 if it uses 800WH? This seems more reasonable, as my solar outdoor tank will only drop from 42C to 37C from 5PM to 8AM - and that's when it's -20C outside.
2. The gizmo you hooked up to track KWH usage......I take from the photo that it is not connected to the HPWH.....since mine doesn't have a clock inside of it? Since there is only one current transformer, does the unit double all the readings itself? Would like to get the same unit, but unsure of how it does its magic.
3. Agree with the "free heat" statement. Our outdoor solar evacuated tube water heater does all our water from May-September, even here in Canada. Since we heat with wood, the heat in the winter is essentially "free" other than my sweat, so the HPWH "should" cut our water heating cost by at least 1/3 if not more. This equates to savings of about $30/mo in hot water costs ( I currently have 240 Hobbs meters connected to the elements in my water heater so I know how many KWH I use per month). Payback then for us is after 2 years ( 7months/year x 2) The added benefit as well is that its load is bearable for an off-grid RE system which is also in the works. The standard 3kw draw of a standard water heater would be hard on the batteries after a while!
Would love to hear a report back as to how yours is working, and if you have any tips for me before I install mine - moving the fan to the outside is already a great idea!