Hydrogen-led fusion plant — power vs H₂ dispatch

What this shows: a low-LCOE fusion plant runs its reactor flat-out and splits the busbar between the grid and a baseload electrolyzer — making H₂ whenever power is cheap and diverting to the grid only during price spikes. Set the plant's cost, the H₂ price, the electrolyzer size, and the grid's price shape; the tool re-computes the grid LCOE after crediting H₂ revenue, the power/H₂ split, and NPV live.

Reactor + turbine run constant — only the electrical routing (grid vs electrolyzer) varies, so fusion never ramps. Electrolyzer: alkaline, 52 kWh/kg (≈19 kg H₂/MWh).
Dispatch rule: each hour, sell to the grid if the price beats the H₂ value (H₂ floor = H₂ price × 19 kg/MWh, net of logistics); otherwise make H₂ up to the electrolyzer's capacity (excess at negative prices is curtailed).
Grid interconnect sized for full output so it can export the peak; the electrolyzer stays highly utilized as the base load.
"H₂-credited" LCOE = (reactor + electrolyzer + logistics cost − H₂ sales) ÷ grid MWh — i.e. what the electricity costs once the H₂ business pays its share.

Plant LCOE $/MWh · underlying fusion cost

$20$35$120

H₂ price $/kg · sale price

$1$3.5$6

Electrolyzer size % of net power

20%90%100%

Grid mean price $/MWh · wholesale avg

$20$40$90

Grid volatility VRE penetration · price spread

0.2×1.0×2×

Model assumptions

Plant: 1 GW_e-class D-T tokamak, ~1,000 MW_e net, constant output, availability 0.85. "Plant LCOE" is the underlying levelized cost you set (a NOAK low-cost plant is the interesting regime).
Electrolyzer: alkaline, 52 kWh/kg → 19.2 kg H₂/MWh; capex $700/kW, O&M 3%/yr, CRF 8%/30 yr (incl. stack replacement in O&M).
H₂ logistics: $0.80/kg (compression + salt-cavern buffer + pipeline/transport), subtracted from the H₂ sale price.
Grid prices: an annual price-duration curve set by the mean and a volatility (VRE) slider; higher volatility deepens the cheap/negative tail and raises scarcity peaks. Negative-price surplus beyond the electrolyzer is curtailed.
Dispatch: sell to grid when price > H₂ floor (= (H₂ price − logistics) × 19 kg/MWh), else make H₂. Reactor/turbine never ramp; only the grid/electrolyzer split changes.
Metrics: the grid LCOE credits H₂ net revenue against total cost over grid MWh (a byproduct-credit view — it turns sharply negative once H₂ over-covers the plant, i.e. electricity becomes the byproduct). NPV = level annual profit × 12.4.

Grid LCOE — after H₂ credit

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Plant NPV (30 yr)

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