I’m looking to expand my solar system by an additional four 330W Panasonic panels which the previous installer quoted me $4400 for the job. To me that is ridiculous since my inverter has plenty of capacity and all they need to do is add the panels in series. There’s plenty of roof space and all they need todo is bolt the hardware to the roof, slap the panels on, and plug them in...the system was designed with expansion in mind. So can anyone share with me your cost for systems being install in the greater Sacramento CA area, or anywhere in NorCal for that matter as a striating point. Seems I should be paying around $3000 for this job? Since I have an existing system does this need a new permit to expand by this small amount...? By my math panels are about $300 online retail, solar optimizes are about $75 and think the total hard cost are about $1700 and my retail...I assume they have better purchasing rates....?