OnSun is a free solar forecast app for iPhone and Android that predicts how much your rooftop panels will produce, and when, through each day of the week ahead, and shows the best time to run each appliance. There is no hardware to install. Enter your panel size, roof direction, tilt and location. The 3-day forecast is free; OnSun Pro unlocks the full week.
The average household exports 50 to 70% of its solar production back to the grid for as little as 4 to 8 cents per kilowatt-hour, then buys that same energy back at night for 25 to 40 cents. Shifting your washing machine, dishwasher, or EV charger into the solar window doesn't require new hardware. It just requires knowing when to press start.
The tools to shift your energy usage into peak solar hours and keep more of what you generate
See your expected solar output for the week ahead. Know which days to run high-draw appliances before the sun rises.
Solar output predicted through each day at the resolution your region's weather data supports, driven by national weather-service forecasts and physics-based solar models.
Get specific recommendations like "Run your washing machine at 11am Tuesday." Shift flexible loads into the solar window.
Track how much grid energy you've avoided and what it's worth. See your self-consumption improve over time.
Pre-configured profiles for washing machines, dryers, dishwashers, EV chargers and more. Set up once, optimise daily.
Gradient visualisations show solar strength across the week. See the sunniest days and peak hours in an instant.
Predicting your solar to save money
Open the app to a clear read on your solar day: a quality rating, the day's peak-sun time, and how much of your generation you actually used. Even on a weak, cloudy day it stays easy to read, and flags when a sunnier day is coming so you can wait for it.
Build tomorrow's plan in a tap. Add an appliance and OnSun drops it into the solar window, showing its start time, the solar coverage it should get, and the savings, with a reminder so you never miss it. Your pool pump at 7:40am, the EV charger at 9:10am.
See the whole week at a glance. Each bar shows that day's solar strength and the savings it unlocked, so you can pick the right day for a big load. This week Sunday peaks at 61 kWh. A running tally adds up everything your planned runs have saved.
Watch your savings compound. OnSun tallies everything you've saved since day one, ranks the appliances pulling the most free solar (your EV charger alone soaked up 153 kWh), and charts solar produced against what you actually used over time.
Start from a library of ready-made profiles: dishwasher, washing machine, dryer, EV charger, pool pump, oven, air conditioner and more. Pick one, set its run time, and OnSun takes care of fitting it into the sun. Adding one is a quick two-step flow.
Use more of your own solar power and reduce your reliance on expensive grid electricity.
Maximise the environmental benefit of your solar panels by using clean energy when it's available.
Let OnSun do the calculations. Just follow the recommendations and watch your savings grow.
No sign-up, any location in the world. See what your roof makes in each season, and whether a battery beats better timing.
Tap your location for a typical summer day, winter day and cloudy day for your panel size, tilt and direction, plus an estimated yearly total.
Should you buy a home battery, or just run the dishwasher at noon? Ten years of both, simulated hour by hour on a year of your own local weather.
At published prices a 13 kWh battery takes a little over nine years to pay for itself on Australia's east coast. Timing appliances is free and worth $200 to $500 a year.
The questions solar owners ask about the app, answered plainly
OnSun is free to download. Enter your panel capacity, direction, and tilt, and you'll see this week's forecast for your roof in about a minute.
Written and modelled by Dr Steven Percy, the engineer who built OnSun. Every figure is sourced, and every saving is an estimate.
In Sydney, Brisbane and Melbourne a 13 kWh battery takes a little over nine years to pay for itself. Running your appliances in daylight is free and worth $200 to $500 a year from the first week. Doing both beats either.
Mid-latitude panels make 2-3x more per day in summer than winter, and 10-25% of normal under heavy cloud. Includes a free tool for your location.
Weather models, sun geometry and your panel specs become an hour-by-hour production curve. Here is how.
Exporting earns 4-8c/kWh; buying it back costs 25-40c. Why self-consumption is where the real savings live.
Usually 10am-3pm, but the window moves daily with the weather and your roof. How to time washing, pool pumps and EV charging.