Assuming this is as reliable effect as implied in the article, a cost-effective method to jump start solar install rates would be to map out roughly 1km wide zones and provide a high and declining subsidies for the first/early people to get solar installed. E.g., go to map and find your house and zone, if five haven't signed up in your zone, it's open, the first to put deposit on install contract gets a $15k subsidy when install complete, $12k for second, $9k for 3rd, $6k 4th, $3k 5th. Adjust zone sizes and/or subsidy amounts for subsidy budget, population density, etc.

Probably a lot cheaper than a $3k subsidy for everyone, as this is only 15 $3k subsidies in each zone. Also probably a lot better to do this with everyone gets a $2.5k subsidy and the first five get the higher incentives.