I would get a Variable Gas Water Heater that can just top up to a set point as needed based on the temperature out of the electric geyser

As is our usual habit, we use hot water once a day - at night, before bedtime.  As such, I don't want a heat pump and all that, specially since gas geysers are coming down in price DRASTICALLY.  This would be for when people come visit, or the once in a blue moon when we need hot water in the morning.  That's it.

On the flipside, it's rainy today (totally cloudy), but batts got to 100% no problem.  Geyser is hot and water tanks are full.  House now pulls 923W now on idle, with my PC running (working), as well as the big 24,000BTU air conditioner set to 21C in the living room.  Inverter ACs are amazing.

On 2024/11/11 at 8:18 AM, Toxxyc said:

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As a result, I've secured financing for a solar system and the quote that I supplied to the bank amounted to R199,219.  This is for an 8kW Deye inverter, 4 x 5.12kWh Dyness batteries and 22 x 540W Canadian Solar panels.  It includes installation, CoC, all accessories and cables, as well as a connection point for a generator that I have already purchased.  The generator isn't massive, and it won't charge the batteries and all that, but if I need to run the house off it for a few hours, I can, and that's good enough for me.  My biggest requirement is that I need a 10 year warranty on the inverter and the batteries.  That limits my options, because if I want that with Sunsynk, I need to install a Sunsynk inverter with Sunsynk batteries.  Sunsynk batteries are overpriced.

I got a price from a well-known place, and the package seems good.  It's a 16kW inverter, with 2 x 5kW batteries and 16 panels, including installation, for R177k.  I'm not sure if it's worth the lower price, but yeah, I'm a bit lost here, and that's why I need some help.

Can you please PM me where you go the quote from and who did you end up going with?

On 2025/01/09 at 9:01 AM, PsyWulf said:

I would get a Variable Gas Water Heater that can just top up to a set point as needed based on the temperature out of the electric geyser

Are they just topping up the temp to a pre set temp? Are they high pressure geysers? This would be a great option if I can go solar with a top up of gas during winter. 

Edited January 25, 20251 yr by BarendD

2 hours ago, BarendD said:

Are they just topping up the temp to a pre set temp? Are they high pressure geysers? This would be a great option if I can go solar with a top up of gas during winter. 

Yes,you get 2 types - the variable one being more pricey because it adjusts based on the input water temp

On 2025/01/25 at 9:04 PM, BarendD said:

Can you please PM me where you go the quote from and who did you end up going with?

In the end I went with Jayceek Electrical: https://electrician.org.za/electricians/gauteng/pretoria/ess-jayceek-electrical-contractor-and-maintence-pty-ltd/

As an update, today is Day 34 off grid.  So far I've had blasting sunny days, and days with so much cloud cover it's hard to get the batteries to 100%.  So far I've generated 1.06MWh, and I've had to use the generator only once.  Only once because I chose to run it when cloud cover was thick, so I can get batteries a bit fuller before bedtime.  I could have skipped it, but I figured the generator needs to run anyway, and "today's as good a day as any", so went with it.

So far, I'm not sorry for a second.  It's worth every single cent.

Saturday was a hot, sunny day, and we had a kid's party.  That involved people camping on the grounds in a caravan with an AC, as well as a jumping castle thing.  Because a lot of power was drawn the whole day, we actually produced more than 50kW during the day from the panels.  Incredible!

The other thing you can do is set your geyser temperature a bit higher, if you have excess sun. That turns it into an additional "battery" - it stores energy as hot water, and when the water is hotter, you need less of it to have a comfortable shower, so it lasts longer.

I made a smart controller for my geyser using a geyserwise thermostat, and a Sonoff THR320 smart relay. It's rated at 20A, so should be ok for your 15A/3kW element. I actually installed a 2kW element so it would have less of an impact on my inverter (also 8kW, like yours). The big thing is that I can automatically (via Home Assistant) monitor the inverter and the battery levels and rate of charge, and adjust the thermostat from 45C normally up to 70C when the batteries are 70% charged, and charging at more than 2.5kW for 5 minutes, and back to 45C when the batteries start discharging at more than 500W for 5 minutes. Total cost around R650, and my 150l geyser soaks up 4kWh of solar taking the water from 45C to 70C (13C/hour at 2kW, takes 2 hours). Obviously, tweak the levels, rates and temperatures according to what works for you.

Depending on how technical you are, and your appetite for complexity, you can also put ESPHome onto the Deye/Sunsynk dongle, or make a new one based on an ESP32 microcontroller and a RS232 transceiver. Then ESPHome on the dongle can talk directly to ESPHome on the Sonoff THR320, and you can skip Home Assistant entirely. Or, an ESP32 with a RS485 transceiver can do the same thing.