Beginner trying to size my system

[Jamie.sanders]

Hello, total newbie to Solar, been reading a lot and tons of videos, so much to learn.

I read my 1st step should be budget, I would like to stay under $6,000 I'm building an emergency or SHTF power backup for the house.

2nd step is I'm trying to size my system, I've found the files here about appliance wattage, and googled some of it for my specific items.

ENERGY USAGE

Absolute max -6,000 watts (taking into account the energy surge of the well, refrigerator and deep freeze kicking on all at the same time by chance.)
absolute minimum -818 watts
normal usage - 3,000 (actually like 2,970)

I've read you want 3 days back up power? so now I'm stuck. not sure how to proceed. How many batteries? how many amps worth of panels?

I plane to put together my own Lifepro4 Eve batteries or equivalent (but how many) 24 or 48 volt? from what I've read 12 volt would not be right for me, and go with Rich solar panels, but again how many?

any help, guidance or references would be greatly appreciated. Thanks in advance.

 

[chrisski]

Not sure how you would build what you’re talking about to provide 6 kw of power for only $6k.

I would think 6000 watts would require 48 volts.

My planning numbers are $15k for a 5kw of panels and install for a grid tied system.

When I start thinking of what you are asking I think I could build something like that for $30k With energy storage. Probably more with three days of back up.

 

[rmaddy]

How many times a year will this system be needed? If it's only for emergencies then maybe it will only be used a couple of times per year. Meaning it will sit unused all but a few days a year. Why not buy a simple gas/diesel generator that can be stored away in a shed or the garage most of the year. Dig it out when needed. Way cheaper and simpler than building a rarely used solar setup with panels, inverter, batteries, etc.

 

[Jamie.sanders]

To answer the above questions, I’m not going to grid tie.
I will use this system 365 days a year. I built my house with dedicated wiring for solar in 3 rooms (extra outlets in the walls that are green), so basic stuff like lights, TV, refrigerator, deep freeze and well will be solar all the time, and the rest as needed when the power goes out, (happens a lot in the winter here in the back woods of Arkansas).

 

[Northernchateau]

ENERGY USAGE

Absolute max -6,000 watts (taking into account the energy surge of the well, refrigerator and deep freeze kicking on all at the same time by chance.)
absolute minimum -818 watts
normal usage - 3,000 (actually like 2,970)

Lets start with fun solar math:
3000 watts / 48 volts = 62.5 amps
62.5 x 24 hrs x 3 days = 4500 amp hrs
or
3000 watts / 24 volts = 125 amps
125 amps x 25 hrs x 3 days = 9000 amp hrs
In either case you will blow past $6000 just in batteries.
My recommendation is to spend the $6k on a back up generator.

 

[chrisski]

I really recommend you look at the DIY blueprints and start doing some pricing yourself.

If your area has permitting, which I don’t see how you’d get around it, that adds more than I would care to deal with. For example, I am adding a 24 volt battery bank that will provide me with 10 kWh of power. A Tesla Power wall is 13 kWh. You mention you want an average of 3 kWh per day. I am paying about $2600 per 10 kWh of usable storage for batteries alone, never mind annoying extra costs like battery housing, hardware and wiring.

You can not get a lithium battery cheaper than that. That comes out cheaper per KWh than the Trojan batteries I bought it to replace. Also, I doubt the county will sign off on a permit for my DIY battery for a household install, never mind you’re asking for something about six times that size.

If you can come down on power requirements, you can get a system for $6k, but you will need to go to propane and give up some appliances.

 

[rmaddy]

To answer the above questions, I’m not going to grid tie.
I will use this system 365 days a year. I built my house with dedicated wiring for solar in 3 rooms (extra outlets in the walls that are green), so basic stuff like lights, TV, refrigerator, deep freeze and well will be solar all the time, and the rest as needed when the power goes out, (happens a lot in the winter here in the back woods of Arkansas).

You may wish to edit your original post to make this clear. As written your OP appears to only be for rare emergency use.

 

[Jamie.sanders]

I really recommend you look at the DIY blueprints and start doing some pricing yourself.

If your area has permitting, which I don’t see how you’d get around it, that adds more than I would care to deal with. For example, I am adding a 24 volt battery bank that will provide me with 10 kWh of power. A Tesla Power wall is 13 kWh. You mention you want an average of 3 kWh per day. I am paying about $2600 per 10 kWh of usable storage for batteries alone, never mind annoying extra costs like battery housing, hardware and wiring.

You can not get a lithium battery cheaper than that. That comes out cheaper per KWh than the Trojan batteries I bought it to replace. Also, I doubt the county will sign off on a permit for my DIY battery for a household install, never mind you’re asking for something about six times that size.

If you can come down on power requirements, you can get a system for $6k, but you will need to go to propane and give up some appliances.

Do u have a link to these DIY blueprints? EDIT, nevermind I found it, As for the county allowing it, I'm in the woods of Arkansas, our county doesn’t really have many laws about anything. Cars don’t need any kind of inspection either. But I’ll look into it

 

[OffGridInTheCity]

Absolute max -6,000 watts (taking into account the energy surge of the well, refrigerator and deep freeze kicking on all at the same time by chance.)
absolute minimum -818 watts
normal usage - 3,000 (actually like 2,970)

I've been running a good sized, off-grid system for a couple of years. The goal is to power my house and I have good stats.

Let's talk May this year - which was peak sun/power for my location. I was able to run 24/7 for the entire month with an average consumption of 2,339watts/hour x 24hrs/day. This was provided by a 12.8kw PV array, an 81kwh battery bank (40% DOD), and dual AIMS 12,000w inverters. Keep in mind that this was 'the best' power production of the year - the winter extreme is only 25% of this.

I also have detailed expenditures. If I do a napkin linear extrapolation from what I spent to $6000 - which should not be that far off - it will put you in the range of: 327watts/hour * 24hrs/day. Or 654watts/hour * 12hrs/day - etc. And I should point out that I built the lithium-ion (18650) battery bank myself and saved 60%? (a lot) of what buying an off-the-shelf battery bank would cost.

 

[chrisski]

I've been running a good sized, off-grid system for a couple of years. The goal is to power my house and I have good stats.

Let's talk May this year - which was peak sun/power for my location. I was able to run 24/7 for the entire month with an average consumption of 2,339watts/hour x 24hrs/day. This was provided by a 12.8kw PV array, an 81kwh battery bank (40% DOD), and dual AIMS 12,000w inverters. Keep in mind that this was 'the best' power production of the year - the winter extreme is only 25% of this.

I also have detailed expenditures. If I do a napkin linear extrapolation from what I spent to $6000 - which should not be that far off - it will put you in the range of: 327watts/hour * 24hrs/day. Or 654watts/hour * 12hrs/day - etc. And I'll point out again that I built the battery myself and saved probably 60-70% of what buying them off the self would cost.

Those are good stats. Answers like that help me plan. Thanks.

 

[Jamie.sanders]

I've been running a good sized, off-grid system for a couple of years. The goal is to power my house and I have good stats.

Let's talk May this year - which was peak sun/power for my location. I was able to run 24/7 for the entire month with an average consumption of 2,339watts/hour x 24hrs/day. This was provided by a 12.8kw PV array, an 81kwh battery bank (40% DOD), and dual AIMS 12,000w inverters. Keep in mind that this was 'the best' power production of the year - the winter extreme is only 25% of this.

I also have detailed expenditures. If I do a napkin linear extrapolation from what I spent to $6000 - which should not be that far off - it will put you in the range of: 327watts/hour * 24hrs/day. Or 654watts/hour * 12hrs/day - etc. And I should point out that I built the lithium-ion (18650) battery bank myself and saved 60%? (a lot) of what buying an off-the-shelf battery bank would cost.

How many and what amp batteries are u running?

 

[OffGridInTheCity]

How many and what amp batteries are u running?

I have an 81kwh battery made up of 84 packs of 260ah each. Each pack is 260ah. The packs are are arranged in 6 x 14s batteries hooked in parallel. BMS is Batrium.