The Problem Index → Power
My solar system works all summer and dies in winter
You sized it on the wrong month. This is the single most common and most expensive off-grid mistake, and the fix is arithmetic you can do in five minutes.
What actually works
◆ Proven
Size the array on DECEMBER sun hours
1.5–3.5 peak sun hours for most of the US, against 5–6 in June. A system sized on the annual average dies on January 9th.
◆ Proven
Mount panels steep — latitude + 15°
Sheds snow and catches the low winter sun. A flat panel under snow produces exactly zero for a week.
◆ Proven
LiFePO4 with a low-temperature charge cutoff
Charging lithium below freezing permanently damages it. The cutoff is mandatory equipment, not a feature.
◆ Proven
Measure the load before resizing anything
A $15 plug-in meter for a week. Standby draw is usually where the budget actually went.
Run the numbers
- Solar array & battery sizing → — free calculator, works offline.
- Battery runtime → — free calculator, works offline.
Also searched as
solar not enough in winter · batteries dead january · solar sizing · off grid solar winter · panels covered in snow · december solar