First DIY Solar/Battery System

[jeff88]

Hello DIYers! I am new to the forum, having researched building my own solar/battery system. I've been looking at a lot of different products to get what works for my situation and was hoping for some advice/input from other experienced people.

TLDR at bottom.

First, a little about me:
I have been in the solar industry since 2014, shortly after graduating with a degree in Energy Management. I've done plenty of electrical work, including solar installs, upgrading electrical panels, etc. so I'm not shy around electricity or installing equipment.

Now, my situation:
I rent my house which makes it very difficult to add anything to it so anything I do needs to be easily and quickly removeable (putting holes in the roof, for example, is out of the question). I have a MSP with a 100A breaker that feeds my sub panel with all of my loads for the house. My 2 large loads are a 40 amp stoven & a 30 amp dryer (both 2 pole). Everything else is lights and plugs. My plan/goal is to intercept the feed at the MSP and install some sort of transfer switch/relay/anything else. Under no circumstances should solar/battery power be sent to the grid (and especially not during a grid outage). So I need a device between the MSP and sub panel to make that "break".
Looking at my utility bills, the typical high consumption day is about 35-40 kWh (and it's not everyday). Based on my calculations, that would require a 200Ah lithium battery & (3) 600ish watt - give or take 50 watts - solar panels. (I can source these at a local supplier I used to buy from when I worked at another solar company.) I have a small flat roof section between the garage roof and the house roof which is slightly south east facing that I plan to use with some sort of ballast system.

So here's my plan:
Source my solar panel of choice: (can I get away with just 3 from a technical standpoint? Will other BOS components have an issue with under voltage or anything else? - I don't want to add in more panels and keep racking up the budgetary cost if I don't have to).
Source my 200-300Ah battery: (probably Amazon, open to suggestions) - I know the typical suggestion is a few days of backup, but this isn't an off-grid system so I'm not worried about it. Is it advantageous for any reason to have multiple smaller ones (besides putting them in series to raise voltage)?
Source control device(s): I am agnostic to all-in-one or individual components, I just need something that fits my needs. I would be perfectly fine with the MOES 80 amp device given that the max my house will never use more than 80 amps (according to NEC 210.20) except the largest wire size MOES designed it for is a #6 which isn't even code compliant! I haven't checked my MSP yet, but I have at least a #4. There are other options out there, but there is usually a spec that doesn't work and I don't want to spend a couple thou- on just the BOS (I was really hoping to keep the whole project under that). I've seen dozens of these types of ATSs, but not sure how confident I am in them yet.

TLDR:
1. From a technical standpoint, can I get away with just (3) 600ish watt panel in a string or will I have other issues down the line with other BOS components?
2. Is it advantageous for any reason to have multiple smaller Ah batteries adding up to my total Ah needs (besides putting them in series to raise voltage)?
3. What device or system (either an all-in-one or a true transfer switch or something else) can transfer power between grid & site power rated for my 100A loads and will not under any circumstances send power back to the grid that can also handle 3 solar panels and a battery?

Thanks for your insight!

 

[再生可能 エネルギー]

1. From a technical standpoint, can I get away with just (3) 600ish watt panel in a string or will I have other issues down the line with other BOS components?

Having only 3 panels, is not that much, especially in winter (December and January).
Can you adjust the inclination of your panels depending of the season,
and do you have any shade, especially in winter when the sun is very low on the horizon?

2. Is it advantageous for any reason to have multiple smaller Ah batteries adding up to my total Ah needs (besides putting them in series to raise voltage)?

Batteries are the most expensive item, so I doubt that you plan to install 40 kWh of batteries to cover your daily usage.
Since you are not off-grid, best is to use your batteries preferably during peak hours. And use the Grid to power your home
during off-peak hours. Also you could charge your batteries during off-peak hours if the 3 panels are not sufficient
to fully charge the batteries, especially during winter.

You should make a consumption audit (using a device like Emporia) to estimate your consumption during off-peak and peak hours.
This will allow you to determine how much batteries you need, at least to cover the peak hour consumption.
You should also check your electrical companies for the different rates offered, especially if you have, or plan to have, an electric car.

3. What device or system (either an all-in-one or a true transfer switch or something else) can transfer power between grid & site power rated for my 100A loads and will not under any circumstances send power back to the grid that can also handle 3 solar panels and a battery?

All-in-One system have their own internal transfer switch, but personally I would prefer using separate components for better efficiency.
So I would turn on the transfer switch only when the batteries are fully charged and only during peak hours.
This would allow to turn off the DC/AC inverter when not needed, to save energy stored in the batteries.

How do you heat your water (electric or gas)? If you have some solar power excess, heating water is an economical way to store enegy.

 

[jeff88]

Having only 3 panels, is not that much, especially in winter (December and January).
Can you adjust the inclination of your panels depending of the season,
and do you have any shade, especially in winter when the sun is very low on the horizon?

I'm not concerned with the number of panels for my usage. If it's only a partial offset in the winter that is fine.
I haven't decided on my mounting system yet, but I can design it to make the pitch whatever I want, including adjustable.
Zero shade whatsoever no matter what time of year.

Batteries are the most expensive item, so I doubt that you plan to install 40 kWh of batteries to cover your daily usage.
Since you are not off-grid, best is to use your batteries preferably during peak hours. And use the Grid to power your home
during off-peak hours. Also you could charge your batteries during off-peak hours if the 3 panels are not sufficient
to fully charge the batteries, especially during winter.

You should make a consumption audit (using a device like Emporia) to estimate your consumption during off-peak and peak hours.
This will allow you to determine how much batteries you need, at least to cover the peak hour consumption.
You should also check your electrical companies for the different rates offered, especially if you have, or plan to have, an electric car.

I'm planning to use a 200 or 300 Ah battery. I'll have plenty of battery capacity to go a whole day of loads on my typical worse day before charging (which won't be necessary since I'll have the panels).
Peak and off-peak are almost the same price - within a few cents - so I'm not worried about that. Based on my calculations I've already designed the system to support my whole energy needs.

All-in-One system have their own internal transfer switch, but personally I would prefer using separate components for better efficiency.
So I would turn on the transfer switch only when the batteries are fully charged and only during peak hours.
This would allow to turn off the DC/AC inverter when not needed, to save energy stored in the batteries.

I'm agnostic to all-in-one or separate components. I can't find a product that works for my needs.

How do you heat your water (electric or gas)? If you have some solar power excess, heating water is an economical way to store enegy.

Gas water heater, no intention of making this project complicated.

 

[再生可能 エネルギー]

Peak and off-peak are almost the same price - within a few cents - so I'm not worried about that.

Is your local eletrical company in San Jose, California, the Pacific Gas and Electric company (or PG&E) ?

If so, here are the new 2024 rates: residential-electric-rate-plan-pricing