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Solar Geyser Panels on east facing roof - newbie questions


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I am starting to look at switching to solar power as much as I can in the next few months and was hoping somebody can give me some advice.

I am thinking of starting with a simple EV tube solar panel setup for one of my two 150l geysers. Because I am planing to go PV solar at a later stage I want to reserve all the north face roofing area for the PV panels. This then leaves either the east facing or west facing roof for the EV tubes. One installer said the panel must go on the west side but I would prefer east for the following reason/assumption - once I have a PV system most of the electricity usage from the panels will be in the morning due to recharging the batteries, washing clothes, ironing, etc and in the afternoon the PV panels will probably have spare capacity that can now be used to assist with the geyser heating. With west facing EV tubes the geyser will not get any heat in the morning unless I want to use Eskom power which I would obviously prefer not to.

Are there any flaws in my reasoning with installing the EV tubes on east facing roof or should I rather listen to the installer and use the west facing roof?

Also would it be a good idea to replace the current element with a lower rated one so that if I do heat they geyser with PV electricity I have more 'spare' power available for other tasks even though the water will take longer to heat.

Thanks for you advice.

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If the roof is true east or true west I dont see the difference the water will heat up in the mornings if its east and cool down during the day and visa versa. However you could cover your north east and west roof with Electric PV this would mean you use a true hybrid inverter not an Axpert Clone this will allow you to power eskom non essential loads from the solar power during the day you will have best of both worlds no intrusive plumbing and you do not need to change much on your geyser maybe a timer to allow it to run during peak solar power.

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8 hours ago, Vassen said:

Honestly, if you are planning on installing pv relatively soon, I would rather not install the evacuated tubes and save the cash and just install a few extra panels on pv and then use the excess power to heat your water. 
 

I also started the same way, installed an additional 200l geyser with 200 evacuated tubes around March / April this year. I didn’t install an element as it prefeeds my 150l geyser. I use a sonoff to measure the water temperature. In winter, on very few days did the water get above 50 degrees. Recently, it gets to between 70 - 80 degrees but on a day like today in JHB, the Water temperature rose less than 5 degrees. 
 

I installed a 2kw element into this 200l geyser last week and now I use my excess power to heat the geyser to 80 degrees after lunch when my batteries are decently full. My 150l is also heated to 65 degrees, the max allowed by geyserwise, at midday everyday. 
 

So if I were to do it again, I would just install the extra storage geyser without the evacuated tubes and then just heat water from excess PV
 

 

I wholeheartedly agree. Considering what I paid for my evacuated tube setup a few years ago, that money would’ve been better spent toward my PV setup and smaller geaser element. At the time, however, PV panels were still R10/W vs R5/W today.

Edited by gbyleveldt
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I was thinking about going full PV originally but that seemed more like a large once-off expense which is why I was thinking of the evacuated tube setup. After seeing the replies I agree that a full PV setup is better and I will probably go with that.

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2 hours ago, Vassen said:

You don’t have to for full solar all at once. You can install it in stages

I did the same. My solar system started 6 years ago and I am still adding, tweaking and tinkering. 
I have an east, a west and a north facing array of PV panels. This way I can produce power at any time of the day. If it rains in the morning, I can produce power in the afternoon or visa versa. I use the excess power to heat my 200L electric geyser. I changed the standard 4kw element for a 3kw and it works perfectly without putting undue stress on the inverter. 
When I queried an EV geyser I was quoted R22K. I did a lot of thinking and eventually decided to add another charge controller and 10 x 330w panels for about the same price as the EV geyser. Now I not only have free hot water, I also have excess power to use elsewhere. 
 

While an EV geyser will be more efficient and take less space on a roof, it has only one function. It only heats the water. PV on the other hand makes power that can be used for anything. 

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