System sizing for "fair weather" off grid.

[Basketcase]

Hello all. I'm wondering if it is possible to reduce the size of a system that is only used during the high production months of the year. I'm talking about my island house that is used from may to september and shut down after that. I'm toying with the idea of adding the fridge to our system which I believe would up our usage to about 2kw hours per day. (1500 for fridge, 500 left for a couple led lights and phone chargers) Do you think that running this off of 680 watts of panels and 230 AH@24v would be cutting it too close? If I want to stay above 50% discharge, that only leaves me 760 watt hours extra. If it matters, I have completely south facing, unobstructed view of the sky. Even on cloudy days I should be able to make some power. There may be times where for a week or 2, nobody is at the house so the fridge would be the only draw, and most likely a lesser one because it will not be opened. I know my calcs are not "complete" but am I even close? A much larger system than this, and it crosses the threshold of being worth doing.

[organic farmer]

I live in Maine. Among the local culture here it is very common for every multi-generation Mainer to own a 'camp'. Some are nothing but bare forest land, some have a cabin and others may be $Million vacation homes with tennis courts and swimming pools. Generally they are intended for use on weekends or maybe 2 weeks of the year.

It is not unusual for camps to have solar power systems, designed for short periods of use.

[Basketcase]

That is pretty much what we have. Right now we have what I estimate to be a 2 to 300 watt 12v array and 2 golf car batteries@230ah at 12v. I'm just wondering if I go to a couple of 340 watt panels and 4 batteries, is that enough to sustain a refrigerator, a few LED lights, and some phone chargers? Doing some generic math, it makes sense. I figure 680w X 4 hours of full sun (conservatively) Thats 2720 watt hours right there. I have to imagine that array would generate over 3k watt hours a day. Then it comes to battery sizing. 230AH @24v is 5520 AH of battery. 50% discharge gets me to 2760 available watt hours per day. If im only using a MAX of 2k, does this design work?

[Mike90250]

That woks fine. Until - some winter holiday and the batteries go dead. So if you stay within your planned mode of operation, and can tolerate 1 or 2 days of clouds & running the generator (even a little eu1000 would work) to make up for the clouds, try it.

[organic farmer]

Does this 'island house' ever experience freezing temps?

If a toilet runs all night, the cycling of a well pump can drain your battery down, and in an unheated room your batteries may freeze. A frozen battery will destroy it's casing. One of my neighbors lost his entire battery-bank this way.

[Basketcase]

The thing that I think makes this system doable is that from May (we are opening May 5th this year) to september (we closed the last week of sept. last year) the house is used. The rest of the year it is shuttered up and vacant. All loads would be removed. I typically shut off the main and let the array "maintain" the batteries over the winter. We used to actually bring the array in every year but I mounted it on the roof and we leave it now.

So there will be no winter holiday, and no freezing temps while the system is in service. The water system is not run from this system, and is shut down for the winter as well.

We will have a generator, but I'd really like to NOT have to rely on it. I'm hoping that since we only use the system during peak production months, that this may work. If it is relevant, this is in Rhode Island.