Current estimates suggest that solar might be as cheap as coal by the end of the decade, and half the cost of coal by the end of the next decade:
If the trend continues for another 8-10 years, which seems increasingly likely, solar will be as cheap as coal with the added benefit of zero carbon emissions. If the cost continues to fall over the next 20 years, solar costs will be half that of coal. These predictions may in fact be too conservative given that First Solar have reported internal production costs of 75 cents (46 pence) per watt with an expectation of 50 cents (31 pence) per watt by 2016.
When applied to electricity prices this predicts that solar generated electricity in the US will descend to a level of 12 cents (7 pence) per kilowatt hour by 2020, possibly even 2015 for the sunniest parts of America.
What does that mean? Cheap, decentralised, plentiful, sustainable energy production. This would be a massive relief to global markets that have been squeezed in recent years by the rising cost of oil extraction, which has been passed onto consumers. Falling energy prices — all else being equal — mean more disposable income to save and invest, or to spend.