[freeranger]

'we only worry when we have a few cloudy days in a row. Eventually we'll have enough to sell back to the power company.'

This is the big problem with small systems - particularly if they are 'off-grid' It's a fine balance to generate and store enough power to meet the household needs - which is a good reason for a wind/solar combination.
Price is always the big problem but it's certainly possible to reduce costs by buying new or second hand equipment at auction sites like ebay. I've been able to buy $2000 solar panels for $300 - $400 each, 120 amp/h deep cycle gel cell batteries for around $150 each and a $3000 inverter for $600. Makes the set up very cost effective.