Watt Options

Will solar pay off on your roof? Would a battery save you anything? Are you on the wrong electricity tariff? Watt Options answers those questions using your own electricity data, not a national average. Import your smart-meter readings, describe the setup you are considering, and it simulates a full year at half-hourly resolution — then costs that year against real Irish supplier tariffs. WHY YOUR OWN DATA MATTERS Most solar calculators ask for one number: your annual kWh. Then they multiply. But whether solar pays off depends on *when* you use electricity, not how much. A house that runs the dishwasher at midday gets a completely different answer from one that comes alive at 6pm — even with identical annual totals. Watt Options works from your actual half-hourly readings, so self-consumption, battery cycling and export all come out of your real behaviour. GET YOUR DATA IN • ESB Networks HDF file — download it from your ESB Networks account and import it directly. No sign-in needed • Home Assistant — read your existing energy statistics over the official API • AlphaESS inverter cloud • Solis and FusionSolar inverter clouds (experimental — switch them on in Settings) No account is needed to use the app. Where you connect a provider, those are your own credentials, encrypted on your device. MODEL WHAT YOU ARE CONSIDERING • Solar PV — panel count, orientation and tilt, with irradiance for your location from the EU's PVGIS dataset • Home battery — capacity, charge and discharge limits, grid charging windows • EV charging — scheduled or diverted from surplus solar • Hot water — immersion diversion and scheduling • Heat pump — demand modelled from your fuel use and local weather COMPARE PROPERLY • Cost any scenario against any supplier plan, including day/night/EV tariffs and standing charges • Microgeneration export counted at your plan's feed-in rate, deemed or metered • Maximum Import Capacity breaches flagged, so you can see them coming • Download a community-maintained list of Irish supplier tariffs, then edit any of them • Compare scenarios side by side — no solar, solar, solar plus battery — and see the difference in euro, not percentages TWO WAYS TO USE IT Quick mode answers "would solar pay off?" in a couple of taps, using sensible defaults. The full interface takes you through it step by step — your usage, then your inverter, panels, battery, hot water, EV and heat pump, one section at a time, each showing a summary of what you have set. Fill in as much or as little as you like; anything you skip simply stays out of the simulation. Run it when you are ready, and the year is costed against every tariff you hold. WHAT IT IS NOT It is not affiliated with any supplier or installer, and it does not sell your details to one. There is nothing to sign up for. Built for Ireland — ESB Networks meter data, Irish supplier tariffs and Irish export arrangements.