How much battery and solar do I need?

[diytx]

I live in Central Texas and want to a take a building off-grid. Still leave it hooked up to coop utility just in case but have it be off the grid. My Summer kWh is really in-line with my Winter. I have some anomalies but it stays pretty level at 35kWh but has spiked to 91.

How much solar should I have and how much battery capacity should I have to be confident moving to a solar/battery only setup?

Last 30 days in kWh;

40
50
32
63
34
33
32
32
38
31
71
75
33
53
91
54
42.5
42.5
15
38
34
32
33
32
36
35
35
35
35
35
34

 

[Hogheavenfarm]

All depends on what you are powering. Makes a huge difference if only running lights and electronics versus running a few mini-splits.

 

[Mattb4]

Not sure that the average is 35kWh per day based on your numbers but leaving that aside for the moment lets use the 35kWh you give. Making some assumptions that you can average 5 hours PV production in Summer and 3 hours in Winter. 35kWh/5h=7kW worth of panels. 35kWh/3h=12kW worth of panels.

If you want to have sufficient battery capacity to store 1 days worth of power than you need 35kWh. If using a 48vDC battery bank that is 35kWh/50vDC=700ah

You inverter must be sized to handle not only the running load but also any starting current that you would face.

If you go with an AIO you can use grid to supplement loading or to handle the large loads so as to not need as big of solar equipment.

 

[diytx]

Water well, ceiling fans, 2 mini splits, lights, conventional water heater, air compressor.

 

[Gason]

Suppose you need 35KWh of electricity every day, a 48V 100Ah lifepo4 battery can store up to 5.12KWh, then you will need 35/5.12=7pcs. A 48V 150Ah lifepo4 battery can store up to 7.68KWh, then you will need 35/7.68=5pcs. This is just a rough estimate, in reality you may need more batteries.

 

[xuba-Aaron]

你可以参考这张图。

 

[DIYrich]

How many days of power do you want if the grid goes down during the next hurricane that comes through, and no sun to recharge?

 

[timselectric]

The only correct answer is "more".

 

[Q-Dog]

The only correct answer is "more".

Came here to say this.

 

[DIYrich]

Wild guess:
10kW of panels (15kW if you don't want to import power except in really rare instances).
Sol-Ark 15k or EG4 18kPV inverter
30 kWh of DIY batteries (two banks of 300ah cells)

Plus, one of the following for emergency backup (grid down):
1) Chargverter with cheap Wen DF427 generator (dual fuel, 240v generator)
2) Hybrid car and connection from High Voltage battery to MPPT input of 5kW charge controller or off-grid inverter.

 

[SamDeleted]

If you really want to go for it, it's 3 days worth of battery capacity - no sun

35 x 3 = 105kwh

But you can get by with a lot less!