07:00
FOR GERMAN SOLAR HOMES

Run it
when the sky says so.

Wattlyzer reads the sun, the spot price, and your roof — then tells you the one best window today to start the dishwasher, the heat pump, the wall box.

Install PWAFree · no account
HOW IT WORKS

Three signals, one window.

No dashboards. No graphs to read. Just the hour you should press start.

01

We read the sky.

Hour-by-hour solar forecast for your roof — pitch, azimuth, kWp and shading included.

02

We read the price.

Dynamic spot tariffs (Tibber, aWATTar, Octopus) pulled fresh four times an hour.

11–14
03

We pick the hour.

One window. Sunniest, cheapest, or balanced — your call. Slide for duration, done.

PRIVACY

Runs on your phone.
Stays on your phone.

Wattlyzer is a Progressive Web App. Forecasts and prices are fetched directly from public APIs. Your roof setup never leaves the device. No account, no tracker, no analytics SDK.

· 01

No account

Configure your roof, you're done. There is nothing to log into.

· 02

No tracking

No analytics, no pixels, no cookies. Open the network tab and check.

· 03

Local first

Tariffs and forecasts cached on-device.

· 04

Open source

Source on GitHub, Apache 2.0 licensed. Read it, fork it, host it yourself.

FAQ

Common questions.

Any dynamic electricity tariff that exposes hourly spot prices. Fixed-rate contracts cannot be optimized — there is nothing to compare.
No. Wattlyzer recommends a window — you start the appliance. We never touch your meter or your inverter.
We use the forecast.solar API with your roof's location, tilt, azimuth, and installed kWp. Accuracy depends on local weather conditions.
Yes. No tier, no upsell. If you want to support the project, star it on GitHub or send a postcard.
Because the App Store would slow shipping, take a cut, and demand an account system we do not need. The PWA installs in two taps from Safari or Chrome.