A new study by Ontario’s electricity market operator suggests wind, solar, and batteries could help meet the province’s future energy needs cheaply, even though the province stands behind a strong role for gas and nuclear power.

As battery energy storage systems (BESS) paired with variable generation (VG) like wind and solar improve their performance and their costs drop, a non-emitting, hybrid resource portfolio shows “significant promise” in theory writes [pdf] Ontario’s Independent Electricity System Operator (IESO).

VG sources can meet both baseload and peak power needs “with reasonably high, albeit imperfect, reliability, and potentially at costs that are competitive with gas and nuclear generation.”

The analysis suggests the geographic diversity of VG sources also improves system reliability.

The findings were published in a study comparing the reliability of VG and BESS against dispatchable resources like nuclear and gas. The IESO emphasized the work was only a modelling exercise, not a plan, and it used simplified assumptions that left out key costs like transmission, labour, and supply chain limits. Its financial assumptions also left out the effects of future policies like clean electricity regulations.

Even so, the results give a sense of how different energy mixes might perform in two scenarios—a “Peaky Need Scenario” that looks at a high peak demand scenario, and a “Baseload Need Scenario” that considers resources to deliver 2,000-megawatt baseload need profile, such as for a large baseload generation facility. The findings suggest that a mix of gas generation and VG with BESS resources is the least-cost option to fulfill the Peaky Need Scenario, while small modular nuclear reactors (SMR) alone were slightly cheaper than gas generation alone to meet the baseload scenario.

However, the study’s SMR assumptions are far more optimistic than what’s been seen in real projects, says [pdf] decarbonization advocacy group Ontario Clean Air Alliance (OCAA).

IESO also assumes that a hybrid resource portfolio—one that includes a mix of VG and BESS with dispatchable sources—would need “excessive overbuild” to reliably meet demand, which would require energy output to be curtailed or intentionally reduced when supply exceeds demand. While the study doesn’t try to quantify the potential curtailment, IESO speculates the value of excess energy might exceed C$36 billion, depending on weather conditions.

But OCAA carried out its own calculation of excess power with the IESO data. The group suggests that using that power to offset system costs—and assuming the excess is not curtailed—could make VG and BESS more affordable than both nuclear and gas in both scenarios.