Load Factor Calculator

Samuel Insull — Thomas Edison's personal secretary turned Chicago utility magnate — popularized the economic use of load factor in the 1890s-1900s. Insull realized that a generating plant sized for peak demand sat idle most of the day; selling off-peak electricity cheaply to industrial customers (like streetcars and ice factories) raised system load factor from ~30% to ~80% and let him undercut competitors' residential rates by 60%. His "two-part tariff" — demand charge for peak kW plus energy charge per kWh — became the industry billing standard in the 1920s.

Utilities still bill commercial and industrial customers this way. Monthly demand charges (often $10–$30 per kW of 15-minute peak) can dominate bills with low load factors: a site drawing 100 kWh over 1 hour pays the same demand as one drawing it over 24 hours, though their energy costs are identical. This is why battery storage, thermal storage (ice banks), and peak-shaving load management have grown rapidly since 2010.

Grid-scale load-factor challenges are now inverted: wind and solar push residual demand lower during the day and steeper at dusk — the "duck curve." The California ISO first publicized the shape in 2013. Modern grid planning treats overall system load factor as less important than the shape and ramp rate of net demand after renewables.

Enter total energy consumed (kWh), peak demand (kW) over the billing period, and the period length in hours. LF = kWh / (peak_kW × hours). A factor of 1.0 means perfectly flat load (energy = peak × time); lower values mean peakier consumption. Typical load factors: residential 0.3–0.5, commercial 0.5–0.7, industrial 0.7–0.9, data centers often above 0.9.

If you're trying to reduce demand charges, focus on your highest-peak 15-minute windows — shifting a few kW of peak to off-peak often beats cutting overall kWh consumption. Everything runs client-side; no values leave your browser.