Every solar PV forecast app I tried asked me things I didn't know. Sun Hours asked two questions, took 8 seconds, and told me exactly when to turn the dishwasher on. Here's what it actually does.
I work shifts. When I got my plug-in solar panels I was dead chuffed — two 400W panels, a microinverter, plugged into the socket in the garage. Job done.
Then I wanted to know what they were actually doing.
I downloaded a solar PV forecast app. It asked me for my system capacity in kWp, my performance ratio, my panel azimuth, my tilt angle in degrees, and my inverter model. I don't know what an azimuth is. I had to Google it.
I downloaded another one. Account required. Then it wanted to connect to my inverter via an API I'd never heard of.
I just wanted to know: is it worth putting the washing on now, or should I wait until noon?
Two questions. That's it.
Sun Hours asks two things:
Your postcode. So it knows your actual local weather — not a vague regional figure, your street.
Your best solar day. The most kWh your panels have ever produced in a day. You've seen that number on your inverter on a good sunny afternoon. That single number tells the app everything it needs to know about your setup — panel size, how you've angled them, any shading — all baked in from real-world performance, not theoretical specs.
Enter those two things. Eight seconds. Done. Your solar PV forecast is ready.
What you actually get
Today, hour by hour. A generation curve showing exactly when your panels peak. Not "it'll be sunny" — an actual kWh forecast for each hour of the day, personalised to your panels and your location.
A 7-day forecast. So you can plan ahead. Big laundry load? Check whether Wednesday is a better solar day than today before you commit to running it now.
A 30-day view. Based on historical sunlight data for your location, you get a full month of expected generation — useful for understanding your seasonal rhythm and setting realistic expectations for winter versus summer output.
Your panel history. The app keeps a record of how your panels have performed on individual days over the past months. At a glance you can see your best days, your worst, and how the season is shifting your output. It's the kind of thing that makes you feel like you actually know what your panels are doing.
The notification that made the difference for me
Because I work shifts, I'm not always around at noon when my panels are doing their best work. I needed something to tell me, not the other way around.
Sun Hours has two optional push notifications you can switch on:
The daily briefing. Every morning, a message telling you how your panels are forecast to perform today. Good day, average day, or don't bother waiting — you know before you've made your first coffee.
The Sun Hours alert. This is the one I use most. When your best two-hour generation window is about to start, your phone buzzes. Literally: go turn on the dishwasher. No checking the app, no guessing. Just an action at the right moment.
For shift workers, people who aren't home all day, or anyone who just doesn't want to think about it — that notification is the whole app in one push.
Travel Mode
Plug-in panels move. Mine have been to my mum's garden, to a campsite in Norfolk, and once very briefly to a festival that turned out to be mostly mud.
Travel Mode lets you update your location with one tap — use GPS or drop a pin anywhere. Your solar PV forecast immediately reflects conditions at that location. Tap again when you're back home and it switches straight back. No reconfiguration, no re-setup.
It's free to use while it's in preview.
No account. No faff.
There's nothing to sign up for. Sun Hours doesn't know who you are and doesn't need to. Your postcode stays on your device. Delete the app and everything goes with it.
The simpler a thing is to open, the more likely you are to actually open it. An app that requires a login gets checked once a month. An app that opens straight to your forecast — and buzzes you when the good hours start — becomes a habit that saves you real money.
Download it free on Google Play. Sol's waiting, sunglasses on. ☀️
Two questions. 8 seconds. Your solar PV forecast is ready.
Your postcode and your best solar day. That's all Sun Hours needs to give you a personalised 7-day solar PV forecast — hour by hour, with push notifications when your peak window opens. Free on Android. No account needed.
Get it on Google Play →