The Energy Regulator Pushes Portugal's Cheap Overnight Electricity Window Back Half an Hour for 2027

Households that have rearranged their laundry, dishwashing and electric-car charging around Portugal's cheaper overnight electricity are about to lose thirty minutes of it. ERSE (Entidade Reguladora dos Serviços Energéticos — Energy Services Regulatory Authority) confirmed on 31 July that, from 2027, the low-price “vazio” (off-peak) period on time-of-use tariffs will begin half an hour later than it does today.

The change sounds trivial, but it lands on the exact window that time-of-use customers have learned to exploit. Portugal offers three broad tariff shapes: a flat “simples” (simple) rate; a “bi-horária” (two-period) rate that splits the day into cheap and expensive blocks; and a “tri-horária” (three-period) rate that adds a peak band. Only the two- and three-period plans are affected — and only their night boundary moves.

By ERSE's own count, that is roughly 497,000 residential contracts: about 386,000 on the two-period tariff and 111,000 on the three-period one. The far larger group — some six million customers on the flat simple rate — sees no change at all, because they pay the same price around the clock.

Why move the clock?

The regulator is redrawing the map to match how electricity is actually priced on the wholesale market. A decade ago the cheapest hours sat deep in the night, when demand collapsed. Today, Portugal's swelling fleet of solar farms floods the grid with cheap power in the middle of the day and leaves the early evening tight, as households switch everything on after sunset. Nudging the off-peak boundary is one small step in a longer effort to make retail tariffs echo those daily swings rather than a twenty-year-old assumption about when the country sleeps.

What it means for your bill

Nobody's rate rises because of the reset itself; the price bands are unchanged. The risk is behavioural. If your dishwasher, water heater or wall-box currently switches on the moment the cheap window opens, it will now spend its first half hour paying the expensive daytime rate unless you push the timer back to match. Anyone running heavy loads right on the boundary should plan to move their schedule by thirty minutes.

The rollout is staggered. Non-residential customers move first, on 1 April 2027. Households follow between 1 July and 31 December 2027, with the switch handled remotely through smart meters — so most people will not have to touch the meter itself, only the appliances and timers they control.

For the roughly half a million homes on time-of-use plans, the practical to-do list is short: confirm which tariff you are on, check where your off-peak window starts, and reset any automatic timers by half an hour once your supplier applies the change. For the six million on the simple rate, it is one more piece of energy paperwork that quietly does not apply.