Going green in certain parts of the US has become an absolute ‘no-brainer’.  Not only does their sunnier climate allow average production of over twice as much energy per equivalent cell as the cloudier UK, and their federal government have similar level of domestic grants as the UK, but certain states give extra incentives.
The green credentials of Arnie are well reported, moving California from an environmental dinosaur to the forefront of renewable innovation (even if the CO2 footprint per person is still far higher than the UK average), and recently unveiling public-private partnership plans for an 8 MW (8,000 kW) system across the University of California.  But, it is Austin, Texas where some of the greatest incentives to install domestic solar have been passed.  Up to 80% of the cost (up to $13,500) is returned through a rebate (further details can be found here).  I am not clear whether federal funding is additional to this, if it is, the systems are essentially free money making device that only require you to stay at home for two days whilst installers work above you.  Even if they are not valid, a conservative back of the stamp estimate, shows that the payback lifetime of the system becomes around 3 years.*  That is excluding the added value that it will give to a house.
I can conceive of very few reasons that every household in Texas wouldn’t want solar photovoltaic cells installed.
Based on non-incentivised payback estimated at 13 years, and that’s using British sunlight figures.