We received an email today asking where the ESP8266 can be purchased from. I guess this is a welcome sign that our websites now receive visitors that are not familiar with this MCU i.e. the general public.
We use the WeMos D1 Mini but you might want to consider the Pro version if your Peacefair Pzem-004T is going to be located a long way from your router. The Pro allows you to connect an external antenna but it does require a minor mod to the development board.
There are clones available which work out around half the price when you factor in postage costs and one of the many sellers on AliExpress is here. Clones are not always identical so it’s up to you to decide if you should buy an original or a copy.