Florida's transmission network is generally robust under normal conditions today.
Constraints in critical corridors will expand in coming years.

These are the HIFLD transmission lines whose two ends lie in different counties, from 69 kV to 500 kV. Line width is each line's thermal rating (a voltage-class estimate). Turn on "Lines inside counties" to see the lines with both ends in one county: they are real, but the county model does not represent them. The study concerns transfers between counties.

The model combines the lines between each pair of neighboring counties into one corridor with their combined rating. It keeps bulk-system circuits ( had no voltage in HIFLD and were identified from the voltages at their ends). Generators come from EIA-860, with plant heat rates and delivered fuel prices from EIA-923; hourly demand is EIA-930 adjusted demand. Over all 8,760 hours of 2023:

• Gas generation within of EIA-923
• Cost of fossil fuel burned $B vs $B reported; $B with utility self-dispatch
• Hourly gas generation correlation
• Net imports from Southern Company TWh vs TWh reported
• No firm load shed at the peak, as in 2023

The map shows the corridors the report names. The full-year model measures a different quantity, the hours a corridor is at its full rating (voltage-class ratings, 8,760 hours of 2023), and does not re-test the report's snapshot results; that layer is in the explorer below ("Hours at limit").

Each county is assigned to the utility serving most of its load, so a territory is a set of whole counties. The interfaces between territories are the corridors that cross their boundaries; line width is the interface capacity (the sum of its corridors' ratings) and color its average loading. Arrows show the model's average 2023 flow. EIA-930 reports the interchange between each pair of connected utilities, the only public data on flows: with statewide pooled dispatch the model's flow direction matches the reported one on of interfaces, and with utility self-dispatch on . Flow magnitudes differ more, and hourly correlations are low: the county model has no utility boundaries inside a county and does not model bilateral schedules. reported ties, including Gainesville's and Homestead's, lie inside counties served mostly by another utility and are not represented.

Blue counties curtail solar because the corridors out of them are at their limit; red counties call interruptible load or have unserved energy. With unlimited transfers the planned fleet serves every hour ( unserved). Across the credible representations interruptible load is – a year. The map shows the base network.

2023 weather, base network. At 1 p.m. the corridors out of Hendry, DeSoto and Baker are at their limit and their solar is curtailed (blue), while the southwest coast and Southeast Florida import as much as the paths allow. Across network representations Broward's shortfall over the year is –, and none in of (); facilities inside a county, such as FPL's Andytown–Oasis project, are not represented. Batteries charge at midday and discharge in the evening.

We ran representations of the network and its dispatch, varying voltage-layer coupling, ratings, the 69 kV layer, normally-open ties and how utilities dispatch. Two of them () shed load in 2023, which did not happen, so 2023 rules them out. A corridor counts as a robust need only if it binds at least 500 hours a year in every surviving representation.

Both are solar-export constraints on kV lines: at least of their binding hours fall in daylight solar hours, with power flowing toward . Their ratings are voltage-class estimates; the owners' actual ratings are the first thing to check (every binding circuit is listed in binding_elements.csv). Add 3 GW of metro data centers and the list grows to include . Double the planned solar and storage and it adds northern paths, including the ties to Southern Company: .

FPL's Andytown–Oasis 500 kV project, approved by the Florida PSC in May 2026 (Docket 20260020-EI), is in service in every 2035 case. Most of its route lies inside Miami-Dade, below county resolution, so it is not evaluated here.

Each bulk circuit was removed in turn at the summer peak, a design-cold winter morning and the solar-heavy midday, and the system re-dispatched within emergency ratings, in each of the network representations (the screen re-dispatches the whole fleet, so utility self-dispatch is not a separate case). In 2035, outages on the 500 kV paths into Southeast Florida (highlighted) cause load loss in Broward (red), each in at most of the representations, so their size depends on how the network is represented; the utilities' detailed planning models can size them.

Each county is shaded by its hosting capability: the largest new firm load it can take at the 2035 summer peak with any single circuit out, without shedding existing customers or calling interruptible load, in the worst network representation (hover a county for the best). It answers a different question from the report's 100 MW cost test. In Southeast and Southwest Florida it ranges from 0 to across representations (3,000 means 3,000 or more). Placing the same 3 GW of data centers at the six strongest nodes instead of six metro counties avoids – of unserved energy and – of interruptible load a year, the multi-load case the report flags. For new generation at a sunny midday, can each take at most more.

Design-cold week: the , peaking at , is served in every credible representation (unserved energy at most , interruptible load at most ). A Southeast-wide cold snap strains Southern Company too: with imports held to the firm contract block, the week has unserved with unlimited transfers and at most unserved and of interruptible load on the networks.

Gas-supply curtailment: half of the FGT-only, gas-only capacity is lost (shaded counties), and dual-fuel units burn oil for the lost gas, with no limit on oil inventory. With unlimited transfers the summer peak week has unserved; with no oil backup either, (cold week: ). On the modeled networks the summer week has – unserved, all in Broward, but – of it occurs with full gas supply: it reflects south Florida's import limits, where the report finds contingencies cost the most, and its size depends on how the network is represented. Without oil backup every network representation falls short in the summer week: –, mostly in Broward, whose large gas plants are listed FGT-only and switch to oil when gas is short.

The map draws EIA's pipeline routes and every gas plant with the pipelines EIA-860 lists for it (hover a plant). EIA-860's coded pipeline fields never name Sabal Trail or Florida Southeast Connection, and they list FGT alone at FPL's Martin and Manatee plants, which Gulfstream also serves. Keeping the plants with a documented second pipeline on gas ( that cannot switch to oil), the summer week has – unserved, practically unchanged: Martin and Manatee are outside the Broward pocket.

Irma, Michael, Ian, Idalia, Helene and Milton each failed lines in proportion to the wind they brought. The map draws each storm's track, colors the corridors it put at risk by how often they failed in 300 draws, and shades counties by the load cut off the bulk system. Ian does the most damage. Averaged over those eight seasons, the transmission-caused shortfall is about a year, but between and if line fragility is 15% better or worse. Pick a storm:

Every candidate targets a corridor that binds in the full-year runs: advanced reconductoring, dynamic line ratings and power-flow control (technologies the report lists as future work), new 230 kV circuits, more Florida–Southern import capability, and the utility-filed projects. Each is valued over full 2035 years in every credible network representation of the utility plans and in the other 2035 scenarios on the base network: Order No. 1920 benefits 2, 3, 4 and 7 in dollars over 20 years, benefits 1, 5 and 6 as indicators. Options are ranked by their worst case across those evaluations. This valuation (full years, discounted at 7%, worst of 10 evaluations) differs from the report's and is not comparable with its 20-year net benefits. keep B/C above 1 in all of them; on the map they are the highlighted corridors.