Your home writes an hourly electricity diary. Here is how to read it

The electricity diary your home writes by itself

For years now, every domestic meter in Spain has been a smart meter. Every hour, yours records how much energy has passed through it and sends that reading to the distribution company, which uses it for billing. The result is an hourly electricity diary of your home, day after day, going back years. And it belongs to you: you have the right to view it and download it.

The striking thing is that hardly any solar quote ever looks at it. Most studies are built on a typical customer, a statistical average profile that does not live in your house, does not cook at your times and does not switch the water heater on when you do. Your consumption curve is the difference between a made-to-measure suit and one-size-fits-all.

Where to see your curve: Datadis and your distributor's portal

The most direct route is Datadis, the official consumption data platform run by the Spanish distribution companies. You can also use your distributor's customer area, which across much of La Costera is i-DE. Both show the same thing: your hourly consumption, ready to view as charts or download as a file.

• Register on Datadis with your ID. The contract holder is the person with access to the data.
• Find your CUPS code on any electricity bill: it identifies your supply point.
• Link the CUPS to your account and request the last year of hourly consumption.
• Download the file or simply use the site's charts: to get started, the charts are enough.

Three signatures that appear in almost every curve

Look at curves from real homes in Xàtiva, Canals or Enguera and the same patterns keep turning up. You do not need technical knowledge to spot them, only to know what to look for.

Sometimes the curve uncovers surprises: night-time consumption nobody could explain turns out to be a poorly programmed pool pump or a water heater with a worn-out thermostat. Naming each signature is the first step towards deciding what installation your home needs, if it needs one at all.

• The night-time hump: a block of consumption between midnight and dawn. Usually an electric water heater programmed for off-peak hours, air conditioning in summer, or both together.
• The phantom standby: a flat line that never drops below a certain level, not even at four in the morning. Routers, set-top boxes, ageing fridges, extension leads that are never switched off. It is consumption you pay for every day of the year.
• The hob peak: short, tall spikes at cooking times. The hob and the oven move a lot of power in a short time, and they reveal when life happens in the kitchen.

System size comes from your curve, not from a catalogue

According to APPA's 2025 sector data, the average residential installation in Spain is around 5.5 kW. It is a useful reference, but it is exactly that: an average. Your curve may call for less, if your daytime consumption is low and steady, or for more, if you work from home, have a pool or run cooling through the summer.

In the Xàtiva area, each well-oriented kWp produces between 1,350 and 1,500 kWh a year according to PVGIS. Crossing that production with your curve, hour by hour, is what lets you calculate how much of your consumption each possible size would genuinely cover, and where adding panels stops paying off. Without the curve, that calculation is a guess.

Orientation: when south is not the answer

A south-facing roof in this district gets close to the maximum, around 1,500 kWh per kWp per year, with production concentrated in the middle of the day. An east-west layout produces between 82% and 85% of that, but spreads the energy across morning and evening.

If your curve peaks early in the morning and again at dusk, the usual pattern for people who leave early, eat out and come home in the evening, an east-west split can match your life better than pure south, even though the annual total is lower. In the old centres of Ontinyent or l'Alcúdia de Crespins, where many roofs pitch east and west, this trade-off comes up all the time. The right answer depends on your curve, not on a general rule.

The battery question is answered by looking at the night

The battery question comes down to a number already sitting in your curve: how much you consume outside daylight hours. If that share is large and cannot be moved, because you dine late, cool the house at night or charge a car, a battery starts to make sense. If you can shift loads to midday, by programming the washing machine, dishwasher or water heater, perhaps you do not need one yet.

It is worth remembering exactly what a battery saves: energy you no longer buy from the grid. In a typical household bill, tolls and charges account for around 40%, and part of that is tied to each kWh consumed, so buying less also trims that part. No battery frees you from the fixed terms. That is why a serious calculation uses your real night-time curve, not a promise of total independence.

Exercise: your curve on a Tuesday and a Sunday

You do not need a spreadsheet or any prior knowledge. Fifteen minutes with the Datadis charts will teach you more about your home than any brochure.

With those three notes you can hold a serious conversation with any installer. And spot, within seconds, anyone presenting you a study without having asked for a single piece of data.

• Pick a recent working Tuesday and the Sunday of that same week.
• Look at 2:00 to 5:00 in the morning: that is your standby. If it clearly exceeds what you would expect from a router and a fridge, something extra is plugged in.
• Look at 13:00 to 15:00 and 20:00 to 22:00: these are the cooking and home-life peaks.
• Compare Tuesday with Sunday: the difference tells you how much being at home weighs, and how much of your consumption would fall in daylight hours if every day were a weekend.
• Write down three things: your night-time standby, your heaviest consumption window, and whether that window gets sun or not.

A study with your numbers, not a typical customer's

Our way of working starts exactly there: before talking about panels, we ask for the curve. With your home's real hourly consumption we size the power, choose the orientation and decide whether a battery comes in now, later or never. Everything else is guesswork with good presentation.

And because we keep watching every installation daily after commissioning, that same curve keeps working: we compare what your roof produces with what your home consumes, and we flag it when something drifts or when an extension starts to pay its way. The data was already yours. Our job is to make it useful.

The curve tells you about the past, and you are going to live in the future

Your consumption curve has one limitation worth stating plainly: it records what your house has done, not what it is about to do. If last year's data includes an oil boiler you plan to retire, or a household with two children leaving for university in September, sizing a solar system on those numbers means designing for a life that will no longer exist.

We see it often around the district. A couple in Canals installing a heat pump next year: their current curve shows not a single kilowatt of that future heating, because today the oil does the job. A neighbour in Xàtiva who has ordered an electric car: his night-time curve is flat, and within a few months he will have a nightly load that appears in no record at all. In both cases the curve alone falls short and needs an honest estimate of what is coming added on top.

That is why a serious study combines both: the real curve as the base, plus a conversation about your plans. Not to inflate the quote, but to avoid ending up short because you only looked in the rear-view mirror. These are the changes that move a curve the most:

• A heat pump or any electric heating replacing oil, wood or gas
• An electric car, even if it arrives in a couple of years
• A swimming pool pump, especially if it runs during daylight hours
• Working from home or retirement: the house starts consuming by day
• Children arriving or moving out
• An extension, a glazed-in terrace or new windows

Reading mistakes that end up costing money

The first is confusing kilowatts with kilowatt hours. Power (kW) is the tap: how much electricity can flow at once. Energy (kWh) is the water that has flowed. The curve measures energy hour by hour, and that is what sizes the system; contracted power is a separate conversation. Mixing them up leads people to ask for as many kilowatts of panels as they have contracted power, a line of reasoning that sounds logical and means nothing.

The second is looking at a single month. An August with the air conditioning on, or a January full of heaters, does not represent your year, and production is not flat either: around Xàtiva a well-oriented roof yields between 1,350 and 1,500 kWh per kWp per year, but that total is spread very unevenly between June and December. Crossing one extreme month of consumption with an annual average of production is the classic recipe for getting the size wrong.

The third is trusting averages. A monthly average flattens the peaks and hides the floor. The floor of the curve, the consumption that never drops (fridge, router, devices on standby), says a lot about a house: if it is high, there are appliances drawing power with nobody using them, and fixing that takes no panels at all, just a while spent checking plugs. An average will not show it; the hourly curve will.

Frequently asked questions