Ten US states including California in 2017 generated more than 20% of their electric power from wind and solar including small-scale PV, evidence that grid operators are having increasing success with integration of renewable resources, according to Energy Information Administration (EIA) data.

The 10 states were Iowa with 37% of electricity generated from wind and solar; Kansas (36%); Oklahoma (32%; South Dakota (30%); North Dakota (27%); Vermont (24%); California (22%); and Maine, Colorado and Minnesota – all 20%.

Of the 10 states with the highest shares of wind and solar generation, most of them were driven by wind. In Iowa, for example, 36.8% was wind and 0.2% solar, EIA reported. California was the most notable exception with a 15.6%-6.4% mix in favor of solar.

Solar was also higher than wind in Arizona and Nevada, both in the Desert Southwest, and in Massachusetts, which has limited onshore wind resource.

During some months in 2017, wind accounted for more than 50% of in-state electricity generation in Iowa and Kansas, while solar exceeded 20% in California during certain months.

The share of wind and solar generation is often highest in either fall or spring, when demand for electricity is relatively low. Generation from solar tends to peak during the summer months.

Data from EIA, the Department of Energy's statistical arm, showed total annual generation from wind and solar last year reached 8% and peaked at 11% in April of that year.

Great Plains states that head the rush to wind do not have renewable energy mandates, in contrast, California and Vermont that are more dependent on solar have aggressive and ambitious ones.

Unlike most other generating technologies, grid operators generally do not dispatch wind and solar generation because these generators produce electricity only when the associated resources are available.

Even so, some wind and solar plants may allow for limited dispatcher control on a minute-to-minute basis.

For example, by setting operating levels to slightly lower than achievable levels for current conditions, operators have some flexibility to increase or decrease output in response to market signals.

With the business case growing for renewables combined with technology gains, the electric utility’s ongoing transition to cleaner energy sources – partly in response to consumer preferences – and mandates for increased usage in some regions of the country, other states will also likely soon produce 20% or more of their electricity from wind and solar.

The most important is Texas, by far the largest consumer of electric power of any state. Wind alone had a 19.8% share of generation this year through July in ERCOT, which serves 90% of the state’s electric load.

Wind

Wind, solar provided 20% or more power in 10 US states in 2017