Is having more off-grid batteries better?

[Chruzz]

A question about how much off-grid battery storage vs solar size.

Estimated Daily Winter Solar Production: 13kWh
Estimated Daily Summer Solar Production: 40—50kWh

Would it be better to have 25kWh battery bank as opposed to a 10kWh battery bank? Given our solar system is only 8.55kW.

It's only two adults, small cabin, gas hot water, gas cooking, no air-con.

Would we better going more batteries or getting a diesel generator to make up for any shortcomings?

 

[Solarcabin Channel]

A battery bank is used for night, low sun days and in a grid blackout (if connected).

Most off gridders design for at least 3 days of capacity to handle at least basic needs for 3 days.

Beyond that 3 days you are probably better off with overpaneling the solar so that bank can charge faster and you have excess on sunny days for running large loads.

A genny can help but you may not be able to get gas in a disaster situation and producing electricity with a genny is expensive.

 

[teal95]

Which is your bigger concern: localized grid outage where you can still get gas for the generator or something more apocalyptic? Last winter an ice storm knocked power out for many around us for 3 days. Fortunately ours only flickered once, despite me being able to look out my window that night and seeing 6 places where the lines were shorting to my trees. I was also around for the blackout ~20 years ago that took out everything for 100 miles for several days. Fortunately for me my car was full of gas and my parents were well outside the power outage.

I know I'm paranoid, but am I paranoid enough?

 

[scrubjaysnest]

Typically the battery bank is sized for your usage and go 3 days without charging. The solar array is then based to charge the battery bank fully with 6 to 8 hours of full sun. Our personal usage is 8 to 10% for overnight. That is from the time the panels quit producing at night until they start again the next morning. This is with propane for heating, cooking, and the refrigerator.
For the off grid set I'll be starting in the spring 4.8 kW battery bank and 1200 to 1800 watts of solar.

 

[OffGridForGood]

A question about how much off-grid battery storage vs solar size.

Estimated Daily Winter Solar Production: 13kWh
Estimated Daily Summer Solar Production: 40—50kWh

Would it be better to have 25kWh battery bank as opposed to a 10kWh battery bank? Given our solar system is only 8.55kW.

It's only two adults, small cabin, gas hot water, gas cooking, no air-con.

Would we better going more batteries or getting a diesel generator to make up for any shortcomings?

Cabin - so you visit on weekends for 2-3 days at a time, but the solar panels collect all week and store in batteries? or you use the cabin for a month at time? this makes a big difference to what you may need to set up.
Estimate of daily consumption in kWh you would have (summer and winter)? It is only one side of the equation to see what solar you expect to collect, what do you expect to use per day? and again, does this vary significantly between summer and winter use?

As far as generators, that depends on how serious a problem it may be for you to have no-power. ie if you had some medical equipment fridge/freezer that is essential, then back up generator may be advisable.
you can plot the solar available and the loads, calculate to three standard deviations the battery required, and think you're good...then a storm or wild-fires come along one day and the smoke blocks all the sun and you wish you had at least a small generator to recharge batteries. I suggest dual fuel type.

 

[TOU47]

We have 2-3 days worth of batteries with little to no sun...if we are careful. We have enough solar to fully charge everything in 3-4 hrs. Obviously too much in the summer (wasteful?) but ideal in the winter or scattered cloud days. That said, I really think I'm going to go up to 5 days battery reserve would be ideal after living off grid the last 2 years. I believe that would allow us to go no generator ever through the winter. (Colorado 6,850 elevation)