To show the importance of efficiency first, I used to use an example comparing light bulbs to a PV system, as follows. But solar lease options on the market have changed the game, making little to no capital outlay and instant energy offset for some systems in states with utility rebates. I know this doesn't exactly answer your question. But maybe it's worth a thought. Efficiency first is the right thing to do, but solar has it's place too.
Ten (10) 100-watt incandescent light bulbs x 10 hours/day = 10kWh/day (3650 kWh/year)
Ten (10 20-watt compact fluorescent bulbs x 10 hours/day = 2 kWh/day (730 kWh/year)
Difference: 2920 kWh/year
One 2,000-watt PV system x 1.45 (*Boulder Colorado - www.pvwatts.org)
$50 for a light bulb vs. $5000 for the PV array*
What would you do?
Having worked in both PV installation field and being an energy auditor I would say that this should not be raised as a question of one VS the other, they should go hand-in-hand, weatherization preceeding solar installation.
Also I would suggest considering solar thermal before solar PV.
This Study posted on the Northwest Energy Star site may be helpful. It has case studies for four or five homes approaching net zero. they summarize the cost of reducing energy needs along with the costs of adding renewables. It also does a fairly good job of summarizing issues we run into when taking energy efficiency to the next level.
Hope this helps.