A load duration curve displays electrical power demand (MW) sorted from highest to lowest across all hours of a year (8,760 hours), forming a monotonically decreasing curve. It is a fundamental tool in power system planning, revealing the proportion of time that load exceeds a given level. The curve naturally segments into peak, intermediate, and base load regions, helping utilities determine the optimal generation capacity mix. The area under the curve represents total annual energy consumption.
# anyplot.ai
# line-load-duration: Load Duration Curve for Energy Systems
# Library: makie 0.22.10 | Julia 1.11.9
# Quality: 89/100 | Created: 2026-06-10
using CairoMakie
using Colors
using Random
Random.seed!(42)
# Theme tokens
const THEME = get(ENV, "ANYPLOT_THEME", "light")
const PAGE_BG = THEME == "light" ? colorant"#FAF8F1" : colorant"#1A1A17"
const ELEVATED_BG = THEME == "light" ? colorant"#FFFDF6" : colorant"#242420"
const INK = THEME == "light" ? colorant"#1A1A17" : colorant"#F0EFE8"
const INK_SOFT = THEME == "light" ? colorant"#4A4A44" : colorant"#B8B7B0"
const INK_MUTED = THEME == "light" ? colorant"#6B6A63" : colorant"#A8A79F"
const IMPRINT_PALETTE = [
colorant"#009E73", # 1 — brand green
colorant"#C475FD", # 2 — lavender
colorant"#4467A3", # 3 — blue
colorant"#BD8233", # 4 — ochre
colorant"#AE3030", # 5 — matte red
colorant"#2ABCCD", # 6 — cyan
colorant"#954477", # 7 — rose
colorant"#99B314", # 8 — lime
]
# Data — synthetic annual hourly load profile for a mid-sized utility
n_hours = 8760
# Build a realistic load duration curve:
# base component + daily/seasonal variation
base_load = 420.0
daily_variation = 150.0 * (0.5 .+ 0.5 .* sin.(range(0, 2π * 365, length=n_hours)))
intraday_variation = 80.0 .* (0.5 .+ 0.5 .* sin.(range(0, 2π * n_hours, length=n_hours)))
noise = 40.0 .* randn(n_hours)
raw_loads = base_load .+ daily_variation .+ intraday_variation .+ noise
# Clamp and sort descending (load duration curve definition)
raw_loads = clamp.(raw_loads, 380.0, 1250.0)
load_mw = sort(raw_loads, rev=true)
hours = 0:(n_hours - 1)
# Capacity tier boundaries (hours)
peak_end = 876 # top 10% of hours
intermediate_end = 4380 # top 50% of hours
# Corresponding load levels at tier boundaries
peak_capacity_mw = load_mw[peak_end + 1]
intermediate_capacity_mw = load_mw[intermediate_end + 1]
base_capacity_mw = minimum(load_mw) + 20.0
# Total energy (area under curve) in GWh
total_energy_gwh = sum(load_mw) / 1000.0
# Plot
const TITLE = "line-load-duration · julia · makie · anyplot.ai"
n_title = length(TITLE)
title_fontsize = n_title > 67 ? round(Int, 20 * 67 / n_title) : 20
fig = Figure(
size = (1600, 900),
fontsize = 14,
backgroundcolor = PAGE_BG,
)
ax = Axis(
fig[1, 1];
title = TITLE,
titlesize = title_fontsize,
titlecolor = INK,
xlabel = "Duration (hours per year)",
ylabel = "Load (MW)",
xlabelsize = 14,
ylabelsize = 14,
xlabelcolor = INK,
ylabelcolor = INK,
xticklabelsize = 12,
yticklabelsize = 12,
xticklabelcolor = INK_SOFT,
yticklabelcolor = INK_SOFT,
xtickcolor = INK_SOFT,
ytickcolor = INK_SOFT,
backgroundcolor = PAGE_BG,
topspinevisible = false,
rightspinevisible = false,
leftspinecolor = INK_SOFT,
bottomspinecolor = INK_SOFT,
xgridvisible = false,
ygridcolor = RGBAf(INK.r, INK.g, INK.b, 0.12),
yminorgridvisible = false,
xminorgridvisible = false,
limits = (0, n_hours, 0, maximum(load_mw) * 1.08),
)
# Fill the three load regions under the curve
peak_hours = 0:peak_end
inter_hours = peak_end:(intermediate_end)
base_hours = intermediate_end:(n_hours - 1)
# Peak region (leftmost, brief spikes) — matte red with low alpha
band!(ax,
collect(peak_hours),
zeros(length(peak_hours)),
load_mw[peak_hours .+ 1];
color = RGBAf(IMPRINT_PALETTE[5].r, IMPRINT_PALETTE[5].g, IMPRINT_PALETTE[5].b, 0.18),
)
# Intermediate region — ochre
band!(ax,
collect(inter_hours),
zeros(length(inter_hours)),
load_mw[inter_hours .+ 1];
color = RGBAf(IMPRINT_PALETTE[4].r, IMPRINT_PALETTE[4].g, IMPRINT_PALETTE[4].b, 0.28),
)
# Base load region (rightmost, always-on) — brand green
band!(ax,
collect(base_hours),
zeros(length(base_hours)),
load_mw[base_hours .+ 1];
color = RGBAf(IMPRINT_PALETTE[1].r, IMPRINT_PALETTE[1].g, IMPRINT_PALETTE[1].b, 0.22),
)
# Main load duration curve
lines!(ax, collect(hours), load_mw;
color = IMPRINT_PALETTE[1],
linewidth = 2.5,
)
# Horizontal dashed capacity tier lines
hlines!(ax, [peak_capacity_mw, intermediate_capacity_mw, base_capacity_mw];
color = [IMPRINT_PALETTE[5], IMPRINT_PALETTE[4], IMPRINT_PALETTE[1]],
linestyle = :dash,
linewidth = 1.5,
)
# Vertical boundary lines between regions
vlines!(ax, [peak_end, intermediate_end];
color = RGBAf(INK_MUTED.r, INK_MUTED.g, INK_MUTED.b, 0.5),
linestyle = :dot,
linewidth = 1.2,
)
# Region labels
text!(ax, peak_end / 2, maximum(load_mw) * 0.92;
text = "Peak\nLoad",
align = (:center, :top),
fontsize = 13,
color = IMPRINT_PALETTE[5],
font = :bold,
)
text!(ax, (peak_end + intermediate_end) / 2, maximum(load_mw) * 0.92;
text = "Intermediate\nLoad",
align = (:center, :top),
fontsize = 13,
color = IMPRINT_PALETTE[4],
font = :bold,
)
text!(ax, (intermediate_end + n_hours) / 2, maximum(load_mw) * 0.92;
text = "Base\nLoad",
align = (:center, :top),
fontsize = 13,
color = IMPRINT_PALETTE[1],
font = :bold,
)
# Capacity tier labels on right margin
label_x = n_hours * 0.94
text!(ax, label_x, peak_capacity_mw + 12;
text = "Peak cap. $(round(Int, peak_capacity_mw)) MW",
align = (:right, :bottom),
fontsize = 11,
color = IMPRINT_PALETTE[5],
)
text!(ax, label_x, intermediate_capacity_mw + 12;
text = "Interm. cap. $(round(Int, intermediate_capacity_mw)) MW",
align = (:right, :bottom),
fontsize = 11,
color = IMPRINT_PALETTE[4],
)
text!(ax, label_x, base_capacity_mw + 12;
text = "Base cap. $(round(Int, base_capacity_mw)) MW",
align = (:right, :bottom),
fontsize = 11,
color = IMPRINT_PALETTE[1],
)
# Total energy annotation (area under curve)
energy_label = "Total annual energy: $(round(Int, total_energy_gwh)) GWh"
text!(ax, n_hours * 0.50, maximum(load_mw) * 0.44;
text = energy_label,
align = (:center, :center),
fontsize = 13,
color = INK_SOFT,
)
# Save
save("plot-$(THEME).png", fig; px_per_unit = 2)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/line-load-duration/makie/code. Any spec id and library id listed in llms-full.txt fit the same URL shape; every URL below is complete and callable.
{
"spec_id": "line-load-duration",
"language": "julia",
"library": "makie",
"page": "https://anyplot.ai/line-load-duration/julia/makie",
"hub": "https://anyplot.ai/line-load-duration",
"code_json": "https://api.anyplot.ai/specs/line-load-duration/makie/code",
"spec_json": "https://api.anyplot.ai/specs/line-load-duration",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/line-load-duration/julia/makie/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/line-load-duration/julia/makie/plot-dark.png",
"quality_score": 89.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Load Duration Curve for Energy Systems on anyplot.ai.