“Free nights/weekends” plans give away energy in a window and charge a high rate the rest of the time. Whether they’re cheap depends entirely on how much of your usage lands in the free window — a number the label assumes (usually 32%) but can’t know about you.
Real example — Reliant Free Overnight 12. Free 9:00 PM to 6:00 AM every day. At the disclosed 32% night share it averages 17.8¢/kWh at 1,000 kWh. Shift none of your usage to nights and the same plan is 25.9¢/kWh — a ~8.2¢ swing on one assumption. That’s why we show these plans as a range, never a single price, and print the break-even share.
Interactive chart — open this example in the tool →
A daytime-heavy home is well under 32%; only an overnight EV charger pushes it far above. Until you import measured interval data, treat the free-share slider’s result as a band, not a promise.