Get the day signal
Power Window requests REE's peninsular real-time market price widget for the selected date. It prefers PVPC hourly prices when available and otherwise uses the spot market price series averaged to hourly values.
Methodology
We separate timing from consumption.
The app gives one grade for when you run the appliance and one label for the estimated electricity consumed by the selected load.
Hourly prices move with flexible supply, demand, and marginal cost.
Power Window does not assume Spain is cheap all day. It reads the hourly signal because the market can change sharply between midday and evening. The practical explanation is:
Downward pressure
- More solar, wind, or hydro output with low variable cost.
- Moderate demand, often around central hours or weekends.
- More storage, exports, or flexible consumption absorbing surplus power.
Upward pressure
- Evening demand rising as solar generation falls.
- Less wind or hydro available in that period.
- Gas-fired generation setting the marginal price, including fuel and CO2 costs.
That is why the app looks for specific windows instead of simply saying "use power at midday". Midday is often good on solar-heavy days, but the hourly data wins.
Estimate the chosen load
For every candidate window, the app multiplies each hour's price by the selected appliance load. Market signal mode keeps this clean. Bill impact mode adds editable per-kWh regulated costs, retailer margin, electricity tax, indirect tax by fiscal territory, and the editable fixed daily social-bonus cost.
cost = sum((EUR per MWh / 1000) * appliance kW)
variable = (market + kWh adders + electricity tax) * indirect tax
shown impact = variable + daily social bonus * indirect tax
Fixed items such as contracted power, meter rental, or the daily social-bonus charge are not used to rank hours because they do not change when you move a dishwasher or EV session.
Normalize against the day
The cheapest average window gets a score near 100 and the most expensive window gets a score near 0. Midday hours receive a small bonus because they often align with stronger solar production, but price remains the main driver.
Show a simple A-F symbol
The A-F grade is a quick interpretation of the score for the selected day. It says whether the selected time window is efficient relative to the rest of that day.
- A 90-100: excellent timing
- B 78-89: very good timing
- C 64-77: decent timing
- D 50-63: below-average timing
- E 35-49: expensive timing
- F 0-34: avoid if flexible
Compare now, today, and tomorrow
When today's data is selected, Power Window compares running immediately with the best remaining window. It also checks tomorrow's day-ahead data when REE has made it available, so the planner can show whether waiting another day is worth considering.
Estimate appliance-style consumption
The colored A-G load label is inspired by appliance energy labels, but it is not an official EU certificate. It is based on estimated run energy:
estimated kWh = selected kW * selected hours
A short dishwasher run may show A or B, while a longer EV charge can show E, F, or G because the total electricity consumed is much larger.