I have a 3kwh element geyser on a timer that is on for an hour from 11h30. I have a solar system with 8kw inverter, 5kwh battery and 6540 w panels
Would it be more efficient if I change the geyser element to a 2kwh and leave it on for 1.5hour instead of 1 hour on the 3kwh element?

Edited June 5, 20251 yr by AndreGreyling

4 minutes ago, AndreGreyling said:

I have a 3kwh geyser on a timer that is on for an hour from 11h30. I have a solar system with 8kw inverter, 5kwh battery and 6540 w panels
Would it be more efficient if I change the geyser element to a 2kwh and leave it on for 1.5hour instead of 1 hour on the 3kwh element?

It would use the same power and do the same heating. It is just kinder to the battery but as you using PV you could have enough PV to use no battery or grid around the 11h30 period. This would depend in which province you are.

There was a time when I had little battery power that I would just switch off my freezer and fridge with smart switches when I was heating water.

You will find the whole management is just so much more relaxing if you could increase your low battery capacity. Yes it does come at a price.

Here you can see that even on a cloudy day like today when I heat water the battery is providing a bit of power with my 5kW Deye.

Edited June 5, 20251 yr by Scorp007

6 minutes ago, AndreGreyling said:

I have a 3kwh geyser on a timer that is on for an hour from 11h30. I have a solar system with 8kw inverter, 5kwh battery and 6540 w panels
Would it be more efficient if I change the geyser element to a 2kwh and leave it on for 1.5hour instead of 1 hour on the 3kwh element?

Hi Andre. You don't have a 3 kWh geyser. You probably have a 3 kW element installed on the geyser. The efficiency impact is negligible to change to a less powerful element. Rather install a GeyserWise to manage water temperature and usage.

17 minutes ago, frivan said:

Hi Andre. You don't have a 3 kWh geyser. You probably have a 3 kW element installed on the geyser. The efficiency impact is negligible to change to a less powerful element. Rather install a GeyserWise to manage water temperature and usage.

Thanks, yes have changed my post!

19 minutes ago, Scorp007 said:

It would use the same power and do the same heating. It is just kinder to the battery but as you using PV you could have enough PV to use no battery or grid around the 11h30 period. This would depend in which province you are.

There was a time when I had little battery power that I would just switch off my freezer and fridge with smart switches when I was heating water.

You will find the whole management is just so much more relaxing if you could increase your low battery capacity. Yes it does come at a price.

Here you can see that even on a cloudy day like today when I heat water the battery is providing a bit of power with my 5kW Deye.

Thanks for the info, much appreciated!

Andre,

I have a larger system than yours, and Bloemfontein's sun is quite a bit sharper than CT's 🤪, but you might want to try what I'm doing:

I installed a CBI Astute smart controller in my control panel (between the inverter and the geyser), and control exactly when the geyser switches on and off every day via my smartphone. My geyser has a 2kW element, drawing about 8.6 amps (or 2000W...), which allow my system to power both the geyser AND still charge my battery from about 09:30 - 10:00. By 13:00 my geyser's built-in thermostat has switched off, and I've used about 6kWh of PV to heat the water. As mentioned, I check the weather each day, and adjust the on and off times using my 'phone to take clouds into account - some days I have to shorten the heating time , or not heat the geyser with PV at all, but there are not many such days....

To directly answer your question: I would change the element to a 2kW unit to allow heating at a lower power level (for a longer time) without the need to revert back to grid power, or to drain your battery.

10 hours ago, HennieL said:

Andre,

I have a larger system than yours, and Bloemfontein's sun is quite a bit sharper than CT's 🤪, but you might want to try what I'm doing:

I installed a CBI Astute smart controller in my control panel (between the inverter and the geyser), and control exactly when the geyser switches on and off every day via my smartphone. My geyser has a 2kW element, drawing about 8.6 amps (or 2000W...), which allow my system to power both the geyser AND still charge my battery from about 09:30 - 10:00. By 13:00 my geyser's built-in thermostat has switched off, and I've used about 6kWh of PV to heat the water. As mentioned, I check the weather each day, and adjust the on and off times using my 'phone to take clouds into account - some days I have to shorten the heating time , or not heat the geyser with PV at all, but there are not many such days....

To directly answer your question: I would change the element to a 2kW unit to allow heating at a lower power level (for a longer time) without the need to revert back to grid power, or to drain your battery.

Thanks, will concider this!