Strictly speaking, this is an appliance and not DIY.
Why did I buy it?
On Sabbath I have been keeping a stove burner on with a cookie sheet over it for what's called a blech.
I keep water hot on it for tea on Sabbath.
The burner uses 800 watts of electricity.
The urn keeps the water hotter, has a special mode for Sabbath, and uses less electricity.
It uses 750 watts of electricity.
I ran the numbers before I bought it, as I always do to make sure an appliance will pay for itself.
If it works for one winter and up to December of the next, it has paid for itself.
Most of you don't observe Sabbath like this so it won't work for you like it does for me.
But it's nice to find something that makes my Sabbath more comfortable
and also helps the environment.