By default the array is sized to your location’s annual average Peak Sun Hours – cheaper, but any below-average month (usually winter) can run a generation deficit even though the year nets out fine. Switch this to “Worst Month” on the Inputs form to size the array against your single lowest-sun month instead, guaranteeing every month is covered – at the cost of a larger array and surplus generation the rest of the year. The Dashboard’s monthly chart is the fastest way to see whether any months are currently running a deficit.