Time-of-use tariffs: savings hinge on 30% night usage

Time-of-use pricing: profitable if a third of spending is nocturnal

According to January BOE prices cited by a forum user, one figure determines everything: €0.063770 per kilowatt-hour. This would be the off-peak rate in time-of-use tariffs, compared to €0.183228 for peak hours and €0.150938 for flat-rate plans without time differentiation. A 47% discount versus a 35% surcharge. The conclusion seems obvious—consuming at night costs less—yet profitability depends on a threshold that no household reaches by accident.

The plan must be requested from the utility company, requires an appropriate smart meter, and opens two daily periods. In winter, the cheap period runs from 0 to 11 and 21 to 24 hours; in summer, from 0 to 12 and 22 to 24. Everything else is peak. As one participant reasons, flattening demand avoids shutting down and restarting power plants, and those willing to shift their consumption receive a reward.

The cited 30% threshold

Circulating calculations suggest that with just 30% of consumption during off-peak hours, the tariff already becomes economically worthwhile. If true, this margin leaves plenty of room: there is no need to reorganize the entire house, just move heavy loads while sleeping or having dinner. Another exercise shared in the conversation indicates that a 42/58 split between peak and off-peak still yields a 10.57% saving based on the prices used then.

Here lies the detail that dismantles the "it doesn't pay off" argument: the comparison is not between using much or little electricity at night, but between the flat rate and a specific distribution. And there are consumptions that can never be moved. The fridge, freezer, and induction hob work when needed. That fixed portion is what can never be recovered.

Real cases: savings from 6.48% to 40%

A record of a specific two-month invoice puts the numbers on the table: 3,303 kWh, 73% off-peak and 27% peak, totaling €538 compared to the €715 that would have been paid without time-of-use pricing. That amounts to a difference of €177 in a single cycle.

Another 45-day invoice, with 107 kWh in peak and 198 in off-peak, closed at around €70 where it would have approached €80 without time differentiation. A 14% saving without forcing anything, just shifting washing machines, dishwashers, and battery charges. At the opposite extreme, those who already do three-quarters of their spending at night—a 75% off-peak share—report reductions exceeding 40%.

There are also less brilliant averages: a 6.48% average saving since the mandatory change, with months where the bill was even higher than with the flat rate. And some expand the scope: those who replaced electric water heaters, storage heaters, and other equipment with more efficient alternatives estimate their investment at €5,600, amortizable in four years according to their calculation.

Soria, penalties, and daylight saving time

The threat hovering over the entire conversation is regulatory. Information held by participants points to penalties 40% higher for customers with time-of-use tariffs, applicable from 876 kWh of annual consumption compared to the 2,280 required for others. Translated: those who behave well with the grid would bear the surcharge of the new tier sooner. Some go further, arguing that the formula could be unconstitutional, recalling a 1997 ruling against an Andalusian water tariff that penalized all consumption for exceeding a threshold.

To this is added a silent enemy: daylight saving time changes. Those accustomed to winter schedules who start the washing machine at eleven at night find themselves heating water during peak hours after the clock change. And washing machines and dishwashers use most energy at the beginning of the cycle, so the surprise on the bill is proportional to the oversight.

Power capacity, social bonus, and skeptics

The change also forces a review of contracted power capacity. Those who had 5.5 kW had to decide between increasing to 5.75 by paying for a new installation certificate or decreasing to 4.6 kW at no cost; three-phase installations must adjust from 10.392 kW to 6.928 with €15 management fee. Equipment installation costs around €10 for the technician, plus another €10 for the limiter if lowering power capacity. The social bonus is compatible: on €15 of consumption, the discount reaches €5.

The strongest counterargument comes from houses with all occupants present daily. If there is unemployment or a baby at home, the entire morning becomes peak time, and running the dishwasher at night does not compensate for the rest. With two salaries and daytime absences, the situation changes completely.

With these differentials, migration to the two-tier tariff should be massive in any household with the house empty during the day. Yet the decision depends on a smart meter, a power capacity adjustment, and habit changes that nobody gives away for free. The figures support the savings; the timelines, not so much.