Energy bills · Guide
Bi-horário vs simples: which Portuguese electricity tariff saves you money?
Switching to a bi-horário (two-period) tariff can cut your bill — or raise it. It all depends on how much of your electricity you can use in off-peak (vazio) hours. Here's the break-even point and how to hit it.
Key takeaways
- With October 2026 regulated prices, bi-horário beats simples once roughly 37% or more of your kWh fall in off-peak hours.
- In the daily cycle, off-peak is 22:00–08:00 every day; the weekly cycle adds long off-peak periods at weekends.
- Water heating, EV/PHEV charging, dishwasher and washing machine are the easiest loads to shift.
- With solar, your daytime grid use falls — which usually makes bi-horário even more attractive.
The three options
- Simples — one price per kWh, all day.
- Bi-horário — a cheaper off-peak (vazio) price and a more expensive price the rest of the time (fora de vazio).
- Tri-horário — three periods: peak (ponta), mid (cheias) and off-peak (vazio).
The break-even point
Using the regulated-market prices ERSE published for October 2026 (ex-VAT): simples €0.1711/kWh; bi-horário €0.2045 outside off-peak and €0.1143 in off-peak. If s is the share of your consumption in off-peak hours, bi-horário is cheaper when 0.2045 × (1 − s) + 0.1143 × s < 0.1711, i.e. when s is above about 37%.
| Off-peak share | Bi-horário average | vs simples €0.1711 |
|---|---|---|
| 20% | €0.1865 | +9% more expensive |
| 30% | €0.1774 | +4% |
| 40% | €0.1684 | −2% cheaper |
| 50% | €0.1594 | −7% |
| 60% | €0.1504 | −12% |
Daily or weekly cycle?
In the daily cycle (ciclo diário) the off-peak period is the same every day: 22:00 to 08:00. In the weekly cycle (ciclo semanal) the weekday off-peak window is shorter, but large parts of Saturday and Sunday are off-peak. If you're home at weekends and can batch laundry and charging then, the weekly cycle can win; otherwise the daily cycle is simpler. Your supplier lists the exact hours for each cycle.
Loads that are easy to shift
| Load | How to shift it |
|---|---|
| Electric water heater (termoacumulador) | Timer or smart relay to heat overnight (or at solar midday if you have panels) |
| EV / plug-in hybrid | Scheduled charging from 22:00 or 00:00 |
| Dishwasher, washing machine, dryer | Delay-start button or a smart plug |
| Pool pump | Split runtime between off-peak and solar hours |
| Heat pump / AC in winter | Pre-heat in off-peak, coast through peak (works best in insulated rooms) |
A smart relay on the water heater alone often moves 20–30% of a household's consumption. If you run Home Assistant, a simple time-of-use automation does the rest — see energy monitoring with Home Assistant.
Bi-horário with solar panels
Solar covers part of your daytime use, so what you still buy from the grid shifts towards evening and night. That raises your off-peak share almost automatically, which is why many solar owners end up on bi-horário. Add a battery and you can even charge it in off-peak hours in winter — see is a home battery worth it?.
Frequently asked questions
What hours are off-peak (vazio) in Portugal?
In the daily cycle, 22:00 to 08:00 every day. The weekly cycle has a shorter weekday window and long off-peak periods at weekends; check your supplier's schedule.
How do I switch to bi-horário?
Ask your supplier; with a smart meter it's usually a remote change. You can also change supplier at the same time if another offer is cheaper.
Is tri-horário worth it?
Only if you can avoid the short, expensive peak periods consistently. For most households bi-horário captures most of the benefit with less hassle.
Sources
- Preço do kWh por fornecedor em 2026 (tarifa simples e bi-horária) — Literacia Financeira (ERSE data) (accessed 29 October 2026)
- Mercado regulado ou mercado livre: onde compensa? — Portal da Queixa (accessed 29 October 2026)