SageBrush wrote: ↑
Sun Aug 04, 2019 10:54 am
^^ That is a grid to be proud of in terms of carbon emissions. I'm jealous.
As for when to use the water heat pump, I think you are right for the summer.
The winter may be different
We will probably run the heat pump water heater during the daylight portion of the 21 hour off-peak winter window before the partial peak 5-8pm hours (no peak hours in winter). Things work out quite nicely as there is little if any solar flux from 5-8pm with early winter sunset time.
Further, ambient temperatures conveniently are highest during sunlit hours, which guarantees heat pump use during highest solar flux ensuring both highest energy transfer efficiency and maximal renewable energy use.
Would love to see reports of PG&E grid energy mix by source and time and day of year to see detailed curtailment patterns to know how best to further play this game for environmental impact. Good to hear similarly minded folks at least as interested in such things.
A bigger issue for us in winter is heat pump ducted air usage to warm the house, especially during the colder nights. No sunlight then and a cost reasonable residential battery solution yet awaits. Would like to see exactly what our PG&E grid is up to with energy input sources and renewable curtailments, if any, during that time. Best I can surmise, non-carbon sources would still be very high at this time.
Grid solar inputs would be relatively low that time of year, so don’t imagine much in the way of needing curtailments there. Not sure if they ramp down NG inputs for electricity generation then since houses aren’t running AC, rather burning NG directly to stay warm instead of a few heat pump folks like our household who actually don’t decrease their winter electricity use.
'19 Model 3 SR+ (own), '19 Leaf SV (leased), '12 Plug-in Prius (sold 3/19), '16 Leaf SV (prior lease), 11.43kW Solar PV (16MWh/yr real production), 20.5 SEER/13.0 HSPF ducted air-source heat pump, 3.70 UEF heat pump water heater, Induction Cooktop