Help needed-battery bank size and budget

[happylisa]

My husband and I look to add battery to our 9.8 KW solar array. We're looking do install by ourselves. How big of battery do we need, and how much should we budget.

 

[Tomthumb62]

My husband and I look to add battery to our 9.8 KW solar array. We're looking do install by ourselves. How big of battery do we need, and how much should we budget.

Welcome to the forum! There’s lots of very smart people here (I’m not necessarily one of them lol).

I’ll say your question is a bit too broad to answer in any meaningful way. If you can add more info, such as the following, you’ll get better answers:

What are your daily loads? In other words, what are you powering and at what times of the day?

Are you going off grid or staying grid tied? This makes a huge difference.

What is your intended use of the battery? A few hours of emergency use during power outages or able to run the entire house for three days of cloudy weather?

 

[sunshine_eggo]

Not much to go on.

10kW array implies a 40-50kWh/day consumption - you should be able to get your consumption data from your system and/or by combined data from the utility.

A 40-50kWh/day consumption requires a 40-50kWh battery. A DIY battery will cost you about $11K. 10X Server rack type batteries will cost you about $17K.

You'll need a 10kW inverter capable of frequency shifting for AC coupling with your grid tie inverter. That will cost you around $6K.

You'll likely need another $2-3K in miscellaneous hardware for wiring, code compliance, etc.

$19K at the low end and $26K at the high end.

This will be a HUGE job for you if you didn't do your own grid tie system. LOTS to learn.

 

[DIYrich]

My husband and I look to add battery to our 9.8 KW solar array. We're looking do install by ourselves.

What inverter do you have? That may dictate what batteries you can easily attach.

How big of battery do we need,

Are you looking to Zero export? Peak Shave? TOU Arbitrage? Grid down (for how long)? What is your daily usage on a bad day? How much does your solar produce?

and how much should we budget.

Tier 1, Tier 2, Tier 3 equipment? Willing to DIY battery? Permitting issues?

 

[DIYrich]

Not much to go on.

10kW array implies a 40-50kWh/day consumption - you should be able to get your consumption data from your system and/or by combined data from the utility.

A 40-50kWh/day consumption requires a 40-50kWh battery. A DIY battery will cost you about $11K. 10X Server rack type batteries will cost you about $17K.

You'll need a 10kW inverter capable of frequency shifting for AC coupling with your grid tie inverter. That will cost you around $6K.

You'll likely need another $2-3K in miscellaneous hardware for wiring, code compliance, etc.

$19K at the low end and $26K at the high end.

This will be a HUGE job for you if you didn't do your own grid tie system. LOTS to learn.

In OH, 10kW array could be 30kWh/day consumption (average over the year, assuming net metering).

DIY 30kWh of battery could be $6,000.

 

[sunshine_eggo]

In OH, 10kW array could be 30kWh/day consumption (average over the year, assuming net metering).

DIY 30kWh of battery could be $6,000.

We're both just making different sets of assumptions due to the fact that no truly meaningful information has been given.

Looks like it really depends on time of year. 34kWh/day average.



When DIYing 48V batteries, you pretty much go in 15kWh increments.

 

[happylisa]

Thanks to you all.

 

[RV10flyer]

In OH, 10kW array could be 30kWh/day consumption (average over the year, assuming net metering).

DIY 30kWh of battery could be $6,000.

You both are still undersized for me in Ky. I consume 30-60kWh summer, 30-80kWh winter. I have 32kWpv and 158kWh battery just for my all-electric home. I run my LP 10kW generator 10 minutes a month just for testing. One needs a lot of power heating, even with high eff heat pumps. I use the woodburner if it’s cloudy below 25F.

 

[DIYrich]

You both are still undersized for me in Ky. I consume 30-60kWh summer, 30-80kWh winter. I have 32kWpv and 158kWh battery just for my all-electric home.

OK. 30kWh for the wife, and 30kWh for the husband.

 

[DIYrich]

We're both just making different sets of assumptions due to the fact that no truly meaningful information has been given.

Looks like it really depends on time of year. 34kWh/day average.

View attachment 164070

When DIYing 48V batteries, you pretty much go in 15kWh increments.

12,632kWh/yr is about 34kWh/day.

You don't need to store the power consumed during the hours of production (Immediatly consumed), so 30kWh of batteries.

 

[RV10flyer]

OK. 30kWh for the wife, and 30kWh for the husband.

Capable of 185kWh average summer day, so a lot goes to waste. Winter, lowest production around 8kWh…that’s a really dark day.

 

[RV10flyer]

Thanks to you all.

Have fun. Keep adding pv and battery until you no longer need the grid or a generator. I thought I was finished last year. Nope still adding and working on a hp water heater.