This is the final curcuit: 

This is components you need for the project:

PZEM-004T: https://s.click.aliexpress.com/e/_9hYStD

ESP8266: https://s.click.aliexpress.com/e/_97j7kp

Resistors: https://s.click.aliexpress.com/e/_9AslPB

Electrolytic Capacitor: https://s.click.aliexpress.com/e/_A2atvx

PCB 6X8: https://s.click.aliexpress.com/e/_d7XpQnS

Pin Header: https://s.click.aliexpress.com/e/_AUvLzT

Female PCB Header: https://s.click.aliexpress.com/e/_AClQip

5V relay module: https://s.click.aliexpress.com/e/_AAXY9i

1602 I2C Display: https://s.click.aliexpress.com/e/_AF3L2o

Compilation

Use core 2.7.4 for this project (Tested with this version)  upd: 08/12/2021 made some changes, tested with 3.0.2 (works)

please download the necessary libraries: https://github.com/electrical-pro/SmartBoard/blob/main/libraries.zip copy them from the archive to: C:\Users\Documents\Arduino\libraries

P.S. I modified the LiquidCrystal_I2C library, I removed Wire.begin(5, 14);

Uploading files from data folder

The project uses SPIFFS to store files on ESP8266, upload them to the ESP8266 (read about SPIFFS if you dont know what that is.) 

 If you don’t see this option install the plugin from here: https://github.com/esp8266/arduino-esp8266fs-plugin

Connecting to router

After flashing connect to “PowerControlESP | Offline” pass is “PowerControlPass” then go to 192.168.4.1 (WI-Fi manager) and connect to your Wi-Fi router. 

Power server is at 192.168.x.x:8089 (port is 8089)

Very unusual authorization that I implemented

If it says “The file exists, but you are not authorized!” – is a simple safety feature that I implemented, so in order to access files you need to go to a secret URL first http://192.168.x.x:8089/me (you can program another one) When you go to http://192.168.x.x:8089/me it puts a cookie in your browser and you become an authorized user

to make it work right set it to false in the sketch

// set it to false, and then get auth cookie by going to 192.168.x.x:8089/me
bool PublicAccess = true;  // authorization 

If it is true it only allows you to go to http://192.168.x.x:8089

if it is false nothing is allowed unless you go to http://192.168.x.x:8089/me first

Serial

Note that I use Serial for PZEM004Tv30 module

PZEM004Tv30 pzem(&Serial);

Other information goes to Serial1 not Serial (so you will not see things in serial monitor)

Serial1.begin(115200);