I’ve signed up for an electric supply retailer that charges the realtime wholesale supply price. So at 1 am the price might be 5c/kWh, while at 6 pm when everyone is using their kitchen appliances cooking dinner, it can be 40c/kWh.

To take real advantage of this though, you need to shift your energy usage to when it’s cheaper. Without a house full of smart appliances, this basically becomes checking the current price before turning the washing machine on.

Sure there’s an app, but my partner doesn’t have it and it’s a hassle to whip the phone out. Glancing at a display is much easier. Utility companies realised people might want that, and have put Zigbee into smart meters to hook up to such In-Home Displays (IHDs). Problem is they tend to look like this:

And you can’t just buy them, since end users can’t hook into their smart meters’ Zigbee network. Sadly this also excludes nerds like us from making use of it.

So let’s make our own! I found these Inky epaper displays for Raspberry Pis. They are limited to black, white and red, and show line art well.

So why not have a rage comic to react to the price?

2024 Update⌗

This little guy is still going strong. I moved into a house that has solar panels, so now it displays solar import price instead of renewable percentage. If imports go negative, the pi even tells the inverter to stop. I also printed a frame/case:¹