Octopus Cosy

Octopus's heat-pump-specific time-of-use tariff with three cheap windows per day designed to align with heat pump duty cycles.

Octopus Cosy is a ToU tariff designed specifically for heat pump households. It has three cheap windows totalling 9 hours per day (typically 04:00-07:00, 13:00-16:00, 22:00-00:00), a moderate "day" rate, and a peak rate from 16:00-19:00 when wholesale prices spike.

As of May 2026, Cosy unit rates are roughly: 13p/kWh cheap, 26p/kWh standard, 39p/kWh peak. For a Cornwall household running an 8kW ASHP, scheduling the heat pump to deliver the bulk of its heat in the cheap windows can cut annual electricity bills by 20-30% versus a flat tariff.

Cosy works best with a heat pump that has weather compensation enabled and a buffer tank or large hot water cylinder, so you can shift load freely without comfort impact. Most Vaillant aroTHERM, Daikin Altherma, Mitsubishi Ecodan and Viessmann Vitocal models are well-suited. See our heat pump page.