Solar.

A battery is like a bank account. It is not possible to bank more than comes in. Having excess storage is not only pointless, but will cause you to lose some of what you have - because battery losses relate to their number and size.

The maximum battery capacity must never exceed that which you can readily fully charge most days. Ideally have about 250 watts of solar per 100 Ah battery capacity. Large solar capacity is fine (and also now cheap). Excess battery capacity is bad (and costly).

Example: A nominally (i.e. what it said in the advt) 250 watts of solar with 5 Peak Sun Hours/day will produce about 175 watts (70% of 250 watts) for five hours/day (that is about 880 watt hours/day). Allowing for charging losses, that will bring a 12 volt 100 amp hour (1200 watt hour) battery from about 35% charge to close to 100% charge in one day. As a good system should be designed to discharge by less than 30% overnight (i.e 70% charge remaining), that gives a healthy margin for occasional deeper charges – and days with less sun.

The best working systems are like this – a lot of solar capacity, not that much battery. This way, the battery will substantially recharge on days of little or next to no sun. And the battery/s will last years longer. (If you need more storage, you must increase solar capacity in at least proportion – ideally higher.)

For many purposes (strongly recommended in my books and used on our previously-owned OKA and Tvan for years) is to run from solar alone. This is simple and works very well. The Tvan and 4.2 litre Nissan Patrol tow vehicle each had totally independent systems, but interconnectable if required (which it never was). This works well if either part requires service.