Vermont’s climate policy relies heavily on solar energy expansion. Meeting the state’s renewable energy goals will require approximately 2,000 acres of land per year devoted to solar panels, or 20,000 acres over the next decade, according to Encore Renewable Energy. But what do the actual performance numbers show for photovoltaic systems in a northern state with long winters, heavy snowfall, and peak electricity demand occurring precisely when solar output is lowest?
Capacity Factor: The Basic Math
A solar panel’s capacity factor measures how much electricity it actually produces compared to its theoretical maximum. According to an analysis of Vermont solar data, a typical small-scale residential installation in middle Vermont achieved a capacity factor of 15%. Utility-scale installations perform better nationally—the U.S. Energy Information Administration reports a 24.2% average in 2022—but Vermont’s northern latitude and predominance of smaller rooftop systems drag performance below that benchmark.
🍁 Make a One-Time Contribution — Stand Up for Accountability in Vermont 🍁
An S&P Global analysis of 2022 monthly data found that Vermont and other northern Atlantic states logged their lowest monthly solar capacity factors in January, falling into “low single-digit territory.”
For comparison, Vermont Yankee nuclear plant operated at a capacity factor exceeding 90% before its 2014 closure, delivering 620 megawatts of consistent output unaffected by weather or season. The plant closed for economic reasons—primarily low wholesale electricity prices driven by cheap natural gas—not due to reliability or safety issues.
The Winter Problem
Solar’s seasonal variation creates a fundamental mismatch with Vermont’s energy needs. According to Lighthouse Solar monitoring data, solar panels produce approximately 40-60% less energy during December and January compared to July and August. Their systems show 65% of annual output occurs between March 21st and September 21st, with only 35% during the other half of the year.
A Duracell Energy analysis found that solar production can be reduced by as much as 80% during winter compared to summer months.
This pattern creates a Vermont-specific problem: the state’s residential sector accounts for 33% of total energy consumption, driven by heating requirements. According to the EIA’s Vermont profile, almost six in ten Vermont households use fuel oil, kerosene, or propane for heating—a larger share than all other states except Maine and New Hampshire.
Peak heating demand occurs on cold winter evenings. Solar output at 7 PM in January: zero.
Snow Coverage Effects
Research on snow’s impact shows variable results. The Northern Alberta Institute of Technology’s five-year study found snow coverage results in approximately 3% annual energy loss—less than earlier industry estimates of 20%.
However, annual figures obscure monthly impacts. A peer-reviewed study in ScienceDirect found that while annual snow losses are generally under 10%, “winter month generation loss due to snow is generally higher than 25%.”
An NREL study of Colorado and Wisconsin systems measured monthly PV losses as high as 90% during specific heavy snow events, though annual losses ranged from 1% to 12% depending on system configuration. Research in ResearchGate documented snow-related yield reductions ranging from 3.5% to 100% depending on accumulation and conditions.
What Vermont Lost
When Vermont Yankee closed December 29, 2014, the state lost its largest electricity source. According to the EIA, Vermont Yankee generated nearly five million megawatthours annually, accounting for over 70% of in-state generation.
The EIA’s Vermont profile notes that since Vermont Yankee’s closure, “more than 80% of Vermont’s electricity supply comes from out of state,” primarily Canadian hydropower.
As of September 2024, Vermont had approximately 333 megawatts of solar capacity installed. But at a 15% capacity factor, that produces the equivalent of roughly 50 MW continuous output—less than one-tenth of Vermont Yankee’s reliable production.
The Timing Mismatch
Vermont’s climate policy assumes electrifying heating systems will reduce emissions. But as S&P Global notes, “heating electrification is expected to push power demand higher in cold weather, increasingly posing the question of grid reliability in the winter months as the share of renewables, notably solar, grows.”
Maximum solar capacity factors align with summer peak demand from air conditioning. Electrifying heating “could lead to winter loads not too far removed from summer levels”—precisely when solar output is at its annual minimum.
Vermont’s answer has been imports. The state signed a 26-year contract with Hydro-Quebec in 2012. Canadian hydropower is renewable, but the arrangement means Vermont’s in-state solar expansion hasn’t reduced dependence on out-of-state generation—it has shifted the source of that dependence. When solar panels are snow-covered and the sun sets at 4:30 PM, imported hydropower fills the gap.
The Bottom Line
Vermont’s installed solar capacity has grown since Vermont Yankee’s closure, now accounting for approximately 16% of in-state generation according to EIA data. But the physics of photovoltaic generation in a northern latitude remain unchanged: capacity factors around 15%, production concentrated in summer months, zero output during winter evenings when heating demand peaks, and winter snow losses that can exceed 25%.
The state that once generated 70% of its electricity from a single reliable source now imports more than 80% of its power. Solar continues expanding, but the question of meeting winter heating demand with summer electricity production remains unanswered.
Dave Soulia | FYIVT
You can find FYIVT on YouTube | X(Twitter) | Facebook | Instagram
#fyivt #VermontEnergy #SolarReality #RenewableEnergy
Support Us for as Little as $5 – Get In The Fight!!
Make a Big Impact with $25/month—Become a Premium Supporter!
Join the Top Tier of Supporters with $50/month—Become a SUPER Supporter!
Subscribe to RSS
Leave a Reply