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
Why Spain has cheap electricity hours
Spain is one of Europe's major solar and wind electricity systems. Renewables now
provide more than half of annual electricity generation, but their output varies strongly
by hour and season. Planning flexible demand around low-price hours can help households
save money and make better use of renewable-rich periods.
The reason is not that Spain is cheap all the time. In the wholesale market, technologies
with very low running costs, like wind and solar, can push more expensive generators out
of the clearing price when renewable output is high and supply is enough to meet demand.
That is why cheap windows can appear around sunny midday hours or windy periods; evenings
can still become expensive when solar falls and demand rises.
The final bill still includes grid charges, regulated costs, taxes, contracted power,
meter rental, and retailer terms. Power Window focuses on the part you can move: EV
charging, laundry, dishwasher cycles, dryers, water heating, or air conditioning.
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.