Buying solar panels and batteries for home backup power - what to consider

Jan

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What you should know before installing solar panels and batteries at your home

There are several factors to consider before investing in solar power for your home, ranging from the specifications of the inverter to the system's impact on your short-term insurance.

South African residents considering solar panels and batteries to power their homes should expect to pay significant sums for the equipment and installation.
 
I just went through the installation process and here is some tips & knowledge I can share:

1) The inverter needs to supply both active power and reactive power. So make sure you have know the rating of the inverter's apparent power (measured in Volts-Ampere) and not just active power (measured in Watts)

2) Look at your house' wiring. You need to be able to split your circuits into essential and non-essential circuits. If you are lucky, all of that can be done on the DB, but you might need to rewire some elements if you are not lucky.

3) My setup on battery (which I think is good) is to have a normal depth of discharge at 30%. That means that day-to-day I only use 70% of the battery's capacity and keep 30% in reserve for power failures. If there is a power failure my setup recharges the battery back up to 30% from the grid. Your battery needs to be sized with that in mind.

4) Make sure your inverter can feed your non-essential circuits if there is excess power!

5) You need to look at both the battery's capacity AND its power delivery ability. It doesn't help if your battery can't feed the inverter fast enough or absorb solar fast enough!

6) Smart switches and home automation pair well with solar. So make sure you can connect your inverter to Home Assistant. Some things you only need to run when you have excess power - e.g. pool pump.

7) Plan how many strings you will have for your solar panels. Longer strings might be slightly cheaper but if one panel in a string is slightly shadowed you lose a lot of generation capacity. Shorter strings mean more effective harvesting.

Mistakes I made:
1) I didn't overprovision solar panels. If you can, do it. You want to maximize your average power generation and not your peak. If you don't use all the peak power then it is no biggy, but having extra generation in the mornings and evenings and cloudy days takes pressure of your battery and grid usage. Solar panels themselves are by far the cheapest component of the installation.

2) I didn't plan properly on how they should do the wiring at my DB which sits in a kitchen cupboard. It doesn't look all that great.

Decisions I made that maybe cost a bit of extra money but I thought was well worth the cost.
1) I went with Victron inverter setup. It is slightly more expensive because it is not an integrated unit, but rather your MPTT, inverter, fuse-box, power meter and reverse flow stop etc are all separate units. Victron pairs well with my Home Assistant, and if something breaks I can replace a component at a time.

2) I went with an installer with 20 years track record. From what I understand that in America a lot of installers went bust and dealing with warranties became a PITA. That being said I got a good price for the gear I bought from them, but some installers will cut corners to give better prices.
 
Johand said:
I just went through the installation process and here is some tips & knowledge I can share:

1) The inverter needs to supply both active power and reactive power. So make sure you have know the rating of the inverter's apparent power (measured in Volts-Ampere) and not just active power (measured in Watts)

2) Look at your house' wiring. You need to be able to split your circuits into essential and non-essential circuits. If you are lucky, all of that can be done on the DB, but you might need to rewire some elements if you are not lucky.

3) My setup on battery (which I think is good) is to have a normal depth of discharge at 30%. That means that day-to-day I only use 70% of the battery's capacity and keep 30% in reserve for power failures. If there is a power failure my setup recharges the battery back up to 30% from the grid. Your battery needs to be sized with that in mind.

4) Make sure your inverter can feed your non-essential circuits if there is excess power!

5) You need to look at both the battery's capacity AND its power delivery ability. It doesn't help if your battery can't feed the inverter fast enough or absorb solar fast enough!

6) Smart switches and home automation pair well with solar. So make sure you can connect your inverter to Home Assistant. Some things you only need to run when you have excess power - e.g. pool pump.

7) Plan how many strings you will have for your solar panels. Longer strings might be slightly cheaper but if one panel in a string is slightly shadowed you lose a lot of generation capacity. Shorter strings mean more effective harvesting.

Mistakes I made:
1) I didn't overprovision solar panels. If you can, do it. You want to maximize your average power generation and not your peak. If you don't use all the peak power then it is no biggy, but having extra generation in the mornings and evenings and cloudy days takes pressure of your battery and grid usage. Solar panels themselves are by far the cheapest component of the installation.

2) I didn't plan properly on how they should do the wiring at my DB which sits in a kitchen cupboard. It doesn't look all that great.

Decisions I made that maybe cost a bit of extra money but I thought was well worth the cost.
1) I went with Victron inverter setup. It is slightly more expensive because it is not an integrated unit, but rather your MPTT, inverter, fuse-box, power meter and reverse flow stop etc are all separate units. Victron pairs well with my Home Assistant, and if something breaks I can replace a component at a time.

2) I went with an installer with 20 years track record. From what I understand that in America a lot of installers went bust and dealing with warranties became a PITA. That being said I got a good price for the gear I bought from them, but some installers will cut corners to give better prices.
Click to expand...
I'm also planning on putting in Victron. I'm looking at 2 x 5kva Multiplus II units in parallel connected to a Cerbo GX. Will add the MPPT controller at a later stage.

What Victron components did you put in?
 
SpiderGear said:
I'm also planning on putting in Victron. I'm looking at 2 x 5kva Multiplus II units in parallel connected to a Cerbo GX. Will add the MPPT controller at a later stage.

What Victron components did you put in?
Click to expand...

1x Multiplus II 5000, Cerbo GX, SmartSolar MPPT 250/100-MC4, Carlo Gavazzi Victron ET112 Energy Meter, Lynx Power In.
 
I installed a 5kva Multiplus II unit and have been very happy with its ability to blend inputs according to rules set for it (and it's open source for easy 3rd party connectivity). I'm replacing my lead-carbon deep cycle batteries though after 3 years as running down to 65% has basically killed them. Today the cost of Lithium based batteries is only a little bit more than lead-acid based batteries, and the usable capacity (of the advertised total capacity) is about 3x greater, and often there is a guarantee of 10 years with a good 3,500 to 4,000 full cycles. From 2022 it is not worth considering lead-acid based batteries any more.

Don't skimp on quality, but rather use some of your home loan money to install properly.
 
I have detailed my experience here over the last 250 odd days

Snyper's Solar Farm

Hi all, I am finally getting round to making this thread. After loads of research and another bout of load shedding I finally decided to pull the trigger and load shed Eskom. Prior to going solar I already had all the lights on LEDs, house is kitted with energy efficient appliances and...
mybroadband.co.za mybroadband.co.za
 
I was going to say there are excellent threads that cost you nothing but some time to read through and try to understand. Most forum members will give the appropriate advice.

@Johand Nice write up. Some food for thought.

I am on my phone (load shedding), so will pick your brain later. Just some clarification questions.
 
Johand said:
2) Look at your house' wiring. You need to be able to split your circuits into essential and non-essential circuits. If you are lucky, all of that can be done on the DB, but you might need to rewire some elements if you are not lucky.
Click to expand...
Did you have to pull additional circuits in the same conduits? I am definitely going to have to get someone to do that, wondering how much effort it is for a skilled electrician.
 
Strange said:
Did you have to pull additional circuits in the same conduits? I am definitely going to have to get someone to do that, wondering how much effort it is for a skilled electrician.
Click to expand...
I got lucky. Could do all my splits at the DB.
 
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