Solar panel forecast
How much will your solar panels make today, tomorrow and over the next week? Enter your panels once and get a 7-day generation forecast in kWh, what your battery will do, and the best times to run the washing machine, dishwasher or EV charger on your own sunshine.
Open the solar panel forecastFree, no sign-up. Works for homes in the UK and worldwide; your settings stay in your browser.
What you get
7-day kWh forecast
Expected generation for each day, how it compares with a clear day at this time of year, and an hourly chart of kW.
Your roof, your panels
Number of panels and wattage, direction and tilt, up to three roofs (east-west splits), losses and inverter limit.
Battery
Charge level through the day, when it fills, and how much you send to or take from the grid.
When to run appliances
The start time with the most spare solar for the washing machine, dishwasher, tumble dryer, immersion heater or EV, or your off-peak hours when the sun won't cover it.
Questions
How much will my solar panels generate tomorrow?
Enter where your panels are, how many you have and their wattage, which way they face and how steep they are. The forecast gives the expected kWh for today, tomorrow and the next 5 days, with an hourly chart and how each day compares with a clear day at that time of year.
Where does the solar forecast come from?
From the sunlight at the ground forecast by weather models: the Met Office UKV (about 2 km) in and around the UK, the Met Office Global model up to 7 days ahead, and NOAA GFS. The direct sun and the diffuse sky light are worked out on your roof's angle, allowing for panel heating, system losses and your inverter limit.
When is the best time to run my washing machine on solar?
Tick the appliances you want to time (washing machine, dishwasher, tumble dryer, immersion heater, EV charging). For each one the forecast finds the start time today or tomorrow when the most of its electricity would come from spare solar, after the house's background use, and gives the share of the run covered. If the sun won't cover it, it points to your off-peak hours.
Does it work with a home battery?
Yes. Enter the battery's usable capacity, charge rate, how full it is now and how much you keep back. The forecast shows the charge through the day, when the battery fills, and how much goes to or comes from the grid.
Does it work for east-west roofs?
Yes. Add up to three roofs, each with its own panels, direction and tilt, for example an east and a west face, or a garage roof.
How accurate is a solar panel forecast?
Day totals are usually more reliable than the timing of each hour. The biggest errors come on days of broken cloud, fog or low cloud, and snow lying on the panels or shading from trees and buildings are not modelled (allow for shading in the losses setting).
Is it free?
Yes. There is no sign-up and no account, and your settings stay in your own browser.
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