April and October are statistically the cheapest energy months for most US households because HVAC load is low, daylight is moderate, and wholesale prices are at seasonal lows. A typical US household uses 540 to 720 kWh in April vs 877 kWh in May and 1,200+ in July/August. The shoulder-season low is also the second-best lock window after August through October.
Why April and October
Mild temperatures mean minimal HVAC runtime. Heating-degree-days and cooling-degree-days both low. Wholesale electricity prices reflect low demand.
Lighting load also moderate (longer days vs winter; not yet peak summer). Total residential kWh consumption drops 30 to 45 percent vs August peak.
Bonus: shoulder-season lock window
April-May and September-October are the cheapest shoulder windows for forward locks. Suppliers price aggressively because wholesale forwards are at seasonal lows.
Best practice: lock in August through October for the optimal forward window. April-May is the secondary window if you missed August through October.
Lock the rate before the next reset.
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