Small scale solar is changing hourly utility demand

2 August 2022

The US Energy Information Administration reports that an increase in electricity generation from small-scale, customer-sited photovoltaic solar in New England is changing the hourly pattern of metered electricity demand during the spring (March–May). Small-scale solar PV means systems with less than 1 MW of generating capacity and typically they are not metered by a utility (referred to as ‘behind the meter’). As a result of the increase in this type of generating capacity in New England, electricity demand on utilities was rapidly decreasing during the morning and rapidly increasing during the evening through the spring months.

Despite New England’s less favourable solar resources, its solar capacity has increased by 3.8 GW since 2016. Small-scale solar generation rapidly increases in the morning, resulting in falling electricity demand, and rapidly decreases in the evening, resulting in rising electricity demand. Because utility grid operators generally dispatch solar generators first, they must ramp up or down other generation types to meet and balance electricity demand.

More than half of New England’s 3.8 GW of PV capacity additions since 2016, or 2.3 GW, have been small-scale solar. Because such generation is not metered by utilities, it is not distinguishable as a source of electricity generation on EIA’s Hourly ‘Electric Grid Monitor’; however, it is assumed to contribute to reduced electricity demand. The solar generation series in the Monitor tracks almost all utility-scale systems of at least 1 MW of capacity.

The addition of small-scale solar has altered the average hourly rate of change in electricity demand in New England. From March through to May of 2016, hourly electricity demand typically increased by 500 MW during the three-hour period between 8:00 am and 11:00 am. By 2022, demand during that period usually decreased by 800 MW.

Similarly, in spring 2016, evening electricity demand typically increased by 800 MW between 4:00 pm and 7:00 pm By 2022, demand increased by 1900 MW during those three hours.

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