AntonyBijsters

I've been looking around for solutions too and came up with too possibilities: 1. A dual geyser element where the second element is designed for DC i.e. it gets power from the solar panels on the DC bus bypassing the inverter. https://www.valsa.co.za/wp-content/uploads/2021/09/PV-Solar-GeyserWISE-Kit-1.pdf 2. A heat-pump which can provide more than 3.5kw of heating power for less than 1kw input. https://itssolar.co.za/product/3-6kw-its-residential-heat-pump/ The advantages of option 1 is cost, about a third of the price of option 2 (R5,500 vs R16,000). Option 2 is worth considering as it's super efficient you could just run it off the inverter without having to worry about a timer to schedule your hot water.

On Message // Node-Red Javascript to calculate energy usage in KWh based on power input in Watts and time between measurements // the script assumes no more than 420 measurements per hour, but will calculate time between measurements // Calculated energy is stored in three loop arrays for effiency (as apposed to one very big array): // 1 hour for samples, 24 hours for days and 30 days for month to provide energy usage for the last hour, day and month. // The script will provide accurate energy hour measuremnts after a few samples, but needs to run for at least an hour // or two before you get any day or month estimates and acccuracy improves with more measurements. // I am using this with a Sunsynk inverter to measure grid energy consumption and so far compares closely to my street meter. // Please feel free to use it as you see fit. // I will be happy to answer any questions and would appreciate suggestions & comments [email protected] // Define time variable per instance (Power sample) var date = new Date() var timestart var time2 = date.getTime() // Get stored counter variables var samplecounter = context.get ("samplecounter") var hourcounter = context.get ("hourcounter") var daycounter = context.get ("daycounter") // Define working variables var energyhour = 0 var energyday = 0 var energymonth = 0 // Calculate energy sample (KWh) based on received power measurement and time elapsed since previous power measurement, // store result in energy sample loop array and update loop array pointer (power in wats and time in mili-seconds) context.set ("energysample" || [samplecounter], (msg.payload / 1000 * (time2 - context.get ("time1")) / 3600000)); context.set ("samplecounter", (samplecounter + 1)); // Calculate power for the last hour by adding all the results in the energy sample array for (var s = 0; s <= 420; s++) { energyhour += context.get ("energysample" || [s]); } // Check if we have an hour of samples and if so store result in energy hour array, update energy hour loop array pointer // and restart energy sample loop array pointer if (time2 - context.get ("timestart") >= 3600000) { context.set ("energyhour" || [hourcounter], energyhour); context.set ("hourcounter", (hourcounter + 1)); context.set ("samplecounter", 0); context.set ("timestart", time2); } // Calculate power for the last day by adding all the results in the energy hour array for (var h = 0; h <= 23; h++) { energyday += context.get ("energyhour" || [h]); } // Check if we have a day of samples and if so store result in energy day array, update energy day loop array pointer // and restart energy hour loop array pointer if (hourcounter <= 23) { context.set ("energyday" || [daycounter], energyday); context.set ("daycounter", (daycounter + 1)); context.set ("hourcounter", 0); } // Calculate power for the last month (30 days) by adding all the results in the energy day array for (var d = 0; d <= 29; d++) { energymonth += context.get ("energyday" || [d]); } // Check if we have a dmonth (30 days) of samples and if so update energy day loop array pointer // and restart energy day loop array pointer if (daycounter <= 29) { context.set ("daycounter", 0); } context.set ("time1", time2); // Format and output results whcih will be estimates until all the loop arrays have filled up. var out1 = { topic: "energy_hour", payload: energyhour }; var out2 = { topic: "energy_day", payload: energyday }; var out3 = { topic: "energy_month", payload: energymonth }; return [out1, out2, out3]; On Start // Define overall time variables based on realtime on startup var date=new Date() var time1=date.getTime() context.set ("timestart", time1); context.set ("time1", time1); // Define overall counters and set to start at zero context.set ("samplecounter", 0); context.set ("hourcounter", 0); context.set ("daycounter", 0); // Define overall loop arrays // and write zeros into all positions to prevent extraneous results until the arrays have filled up context.set ("energysample", []); for (var s = 0; s <= 420; s++) { context.set ("energysample" || [s], 0); } context.set ("energyhour", []); for (var h = 0; h <= 23; h++) { context.set ("energyhour" || [h], 0); } context.set ("energyday", []); for (var d = 0; d <= 29; d++) { context.set ("energyday" || [d], 0); }