Household finances
Small timing choices compound
A single dishwasher run is not life-changing. An EV charge is larger. Repeated
across weeks and months, shifting flexible loads away from expensive hours can
reduce the variable part of a household electricity bill.
The app is intentionally conservative: it ranks hours using the selected day's
hourly market signal and keeps fixed monthly items separate, because contracted
power and meter rental do not change when a flexible load moves from one hour to
another.
Today and example week
€0.33
Dishwasher: 2 PM-4 PM instead of 8 PM-10 PM
€4.17
EV: 2 PM-5 PM instead of 7 PM-10 PM
€0.29
Laundry: 2 PM-4 PM instead of 8 PM-10 PM
€15.09-€19.78
Example week: 2 dishwasher, 1 laundry, 3-4 EV top-ups
Example from 7 July 2026 PVPC prices and the first 7 available July days using
bill-impact defaults. The weekly basket is illustrative, not a claim about every
home.
Grid usefulness
Demand can help follow supply
Spain has a growing solar-heavy electricity mix, so many low-price windows happen
during bright daytime hours. That does not mean midday is always best. It means a
planner should check real hourly data and make flexible demand easier to place when
the system is already sending a cheaper signal.
The wider principle is demand response: shifting or reducing electricity use to
help balance the grid. The International Energy Agency describes demand response
as increasingly important as grids include more variable wind and solar generation.
Why EVs matter
Cars are movable batteries of demand
EV charging is often the largest flexible load at home. A 20 kWh top-up can be
many times larger than a dishwasher cycle, and most cars do not need to start
charging the moment they are plugged in.
Power Window turns that flexibility into a simple choice: set the car, battery
level, target, and charger power, then see which remaining hours are cheapest.
What we will not claim
This is a signal, not a guarantee
Power Window does not know your network constraint, retailer contract, charger
losses, battery limits, or local distribution grid. It is not a grid-control
system and it does not promise carbon savings for every hour.
The mission is smaller and more practical: make the flexible part of electricity
use visible enough that better timing becomes normal.