So you have to assume the power being used is constant during each 2s cycle.
2secCost = ((WH / 1000.0) * energyTariff ) * ( 2 / 3600);
CumumlativeCostToday = CumumlativeCostToday + 2secCost;
(2 / 3600) converts the cost of running for 1 hour into the cost of running for 2 seconds.
Second line of code just keeps adding an extra 2s cost to the running total.
Need to virtualWrite() the CumumlativeCostToday to the server and sync it back when the ESP reboots.
float CumumlativeCostToday = 0;
float 2secCost = 0;
void TodayCumumlative() {
2secCost = ((WH / 1000.0) * energyTariff ) * ( 2 / 3600);
CumumlativeCostToday = CumumlativeCostToday + 2secCost;
Blynk.virtualWrite(16, CumumlativeCostToday);
Blynk.syncVirtual(16);
}
I added like this
Move this to
BLYNK_CONNECTED(){
}
Presumably in V16 you have something like:
BLYNK_WRITE(V6){
CumumlativeCostToday = param.asFloat();
}
float CumumlativeCostToday = 0;
float t2secCost = 0;
timer.setInterval(5000L, GetUpdates);
BLYNK_WRITE(V16){
CumumlativeCostToday = param.asFloat();
}
void GetUpdates() {
t2secCost2 = ((WH / 1000.0) * energyTariff ) * ( 2 / 3600);//
CumumlativeCostToday = CumumlativeCostToday + t2secCost; //
Blynk.virtualWrite(V16, CumumlativeCostToday);
}
BLYNK_CONNECTED(){
Blynk.syncVirtual(16);
}
Cant get update from Value display v16, waited long time but no result,
my guest is I am not doing right 
Do you have all the required elements for Blynk Timer in your sketch?
setInterval normally goes in setup() after Blynk connection.
Presumably you have WH declared as a global variable and you need the code to read the ACS sensor to give you the value for WH.
Slip a Serial.println() into GetUpdates() etc.
I guess I did.
yes it is in setup
I did not quite understand that 
which is in
void getACS712()
here ?
Post a basic sketch that you are having problems with and someone might take a look at it. Impossible to debug just with extracts.
I guess it is your sketch
#define BLYNK_PRINT Serial
#include <ArduinoOTA.h>
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>
#define CLOUD // comment out for local server
BlynkTimer timer;
char auth[] = "xxxx";
char ssid[] = "xxxx";
char pass[] = "xxxx";
char server[] = "blynk-cloud.com"; // ip or domain
char myhostname[] = "ACS712"; // for OTA and router identification
const int sensorIn = A0;
unsigned int mVperAmp = 185; // 185 for 5A, 100 for 20A and 66 for 30A Module
float ACSVoltage = 0;
float VRMS = 0;
float AmpsRMS = 0;
float inputV = 238.0; // reading from DMM
float mcuVoltage = 5.0; // MCU ADC maximum - voltage divider means we should use 5.0V reference not 3.2V
float WH = 0;
unsigned int calibration = 62; // V2 slider calibrates this
unsigned int pF = 95; // Power Factor default 90
float energyCostpermonth = 0; // 30 day cost as present energy usage incl approx PF
unsigned int energyTariff = 21; // http://www.energysavingtrust.org.uk/about-us/our-calculations
float CumumlativeCostToday = 0;
float t2secCost = 0;
void getACS712() { // for AC
ACSVoltage = getVPP();
VRMS = (ACSVoltage/2.0) *0.707;
VRMS = VRMS - (calibration / 10000.0); // calibtrate to zero with slider
AmpsRMS = (VRMS * 1000)/mVperAmp;
if((AmpsRMS > -0.015) && (AmpsRMS < 0.008)){ // remove low end chatter
AmpsRMS = 0.0;
}
Serial.print(String(AmpsRMS, 3));
Serial.print(" Amps RMS");
Serial.print("\tPower: ");
WH = (inputV * AmpsRMS) * (pF / 100.0);
Serial.print(String(WH, 3));
Serial.print(" WH");
Blynk.virtualWrite(V0, String(AmpsRMS, 3));
Blynk.virtualWrite(V1, String(WH, 3));
Blynk.virtualWrite(V3, int(WH + 0.5)); // gauge
energyCostpermonth = 24.0 * 30.0 * (WH / 1000.0) * (energyTariff);
Serial.print(" Approx cost per month: Tg");
Serial.println(String(energyCostpermonth, 2));
Blynk.virtualWrite(V6, String(energyCostpermonth, 2));
}
float getVPP()
{
float result;
int readValue;
int maxValue = 0;
int minValue = 1024;
uint32_t start_time = millis();
while((millis()-start_time) < 950) //read every 0.95 Sec
{
readValue = analogRead(sensorIn);
if (readValue > maxValue)
{
maxValue = readValue;
}
if (readValue < minValue)
{
minValue = readValue;
}
}
result = ((maxValue - minValue) * mcuVoltage) / 1024.0;
return result;
}
// V0 AC IRMS display
// V1 WH display
BLYNK_WRITE(V2) { // calibration slider 50 to 70
calibration = param.asInt();
}
// V3 WH gauge
BLYNK_WRITE(V4) { // set supply voltage slider 70 to 260
inputV = param.asInt();
}
BLYNK_WRITE(V5) { // set 5, 20 or 30A ACS712 with menu
switch (param.asInt())
{
case 1: { // 30A
mVperAmp = 66;
break;
}
case 2: { // 20A
mVperAmp = 100;
break;
}
case 3: { // 5A
mVperAmp = 185;
break;
}
default: { // 30A
mVperAmp = 66;
}
}
}
// V6 Cost gauge
BLYNK_WRITE(V7) { // PF slider 60 to 100 i.e 0.60 to 1.00, default 95
pF = param.asInt();
}
BLYNK_WRITE(V8) { // Energy tariff slider 1000 to 2000, default 1437 (UK £ 0.1437 / KWH)
energyTariff = param.asInt();
}
BLYNK_WRITE(V16){
CumumlativeCostToday = param.asFloat();
}
void GetUpdates() {
t2secCost2 = ((WH / 1000.0) * energyTariff ) * ( 2 / 3600);//
CumumlativeCostToday = CumumlativeCostToday + t2secCost; //
Blynk.virtualWrite(V16, CumumlativeCostToday);
}
void setup() {
WiFi.hostname(myhostname);
Serial.begin(115200);
Serial.println("\n Rebooted");
WiFi.mode(WIFI_STA);
#ifdef CLOUD
Blynk.begin(auth, ssid, pass);
#else
Blynk.begin(auth, ssid, pass, server);
#endif
while (Blynk.connect() == false) {}
ArduinoOTA.setHostname(myhostname);
ArduinoOTA.begin();
timer.setInterval(2000L, getACS712); // get data every 2s
timer.setInterval(5000L, GetUpdates);
}
BLYNK_CONNECTED(){
Blynk.syncAll();
Blynk.syncVirtual(16);
}
void loop() {
Blynk.run();
ArduinoOTA.handle();
timer.run();
}
Mods to do:
Don’t do syncall and syncVirtual together - just sync what you actually need not “all”.
Don’t use 2 timed loops, put content of GetUpdates() towards the end of getACS712().
Test, provide feedback and an updated sketch if it’s still not working.
Don’t forget Serial.println() for a few of the variables at the end of your revised getACS712(). You might need lots of decimal places to see the values.
GetUpdates() is also totally wrong because you were using a 5s timer and the formula is for 2s energy usage snapshots. That’s why the code needs to be in getACS712().
#define BLYNK_PRINT Serial
#include <ArduinoOTA.h>
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>
#define CLOUD // comment out for local server
BlynkTimer timer;
char auth[] = "xxxx";
char ssid[] = "xxxx";
char pass[] = "xxxx";
char server[] = "blynk-cloud.com"; // ip or domain
char myhostname[] = "ACS712"; // for OTA and router identification
const int sensorIn = A0;
unsigned int mVperAmp = 185; // 185 for 5A, 100 for 20A and 66 for 30A Module
float ACSVoltage = 0;
float VRMS = 0;
float AmpsRMS = 0;
float inputV = 238.0; // reading from DMM
float mcuVoltage = 5.0; // MCU ADC maximum - voltage divider means we should use 5.0V reference not 3.2V
float WH = 0;
unsigned int calibration = 62; // V2 slider calibrates this
unsigned int pF = 95; // Power Factor default 90
float energyCostpermonth = 0; // 30 day cost as present energy usage incl approx PF
unsigned int energyTariff = 21; // http://www.energysavingtrust.org.uk/about-us/our-calculations
float CumumlativeCostToday = 0;
float t2secCost = 0;
void getACS712() { // for AC
ACSVoltage = getVPP();
VRMS = (ACSVoltage/2.0) *0.707;
VRMS = VRMS - (calibration / 10000.0); // calibtrate to zero with slider
AmpsRMS = (VRMS * 1000)/mVperAmp;
if((AmpsRMS > -0.015) && (AmpsRMS < 0.008)){ // remove low end chatter
AmpsRMS = 0.0;
}
Serial.print(String(AmpsRMS, 3));
Serial.print(" Amps RMS");
Serial.print("\tPower: ");
WH = (inputV * AmpsRMS) * (pF / 100.0);
Serial.print(String(WH, 3));
Serial.print(" WH");
Blynk.virtualWrite(V0, String(AmpsRMS, 3));
Blynk.virtualWrite(V1, String(WH, 3));
Blynk.virtualWrite(V3, int(WH + 0.5)); // gauge
t2secCost = ((WH / 1000.0) * energyTariff ) * ( 2 / 3600);//
CumumlativeCostToday = CumumlativeCostToday + t2secCost; //
energyCostpermonth = 24.0 * 30.0 * (WH / 1000.0) * (energyTariff);
Serial.print(" Approx cost per month: Tg");
Serial.println(String(energyCostpermonth, 2));
Serial.println(String(CumumlativeCostToday, 2));
Blynk.virtualWrite(V6, String(energyCostpermonth, 2));
Blynk.virtualWrite(V16, String(CumumlativeCostToday, 2));
}
float getVPP()
{
float result;
int readValue;
int maxValue = 0;
int minValue = 1024;
uint32_t start_time = millis();
while((millis()-start_time) < 950) //read every 0.95 Sec
{
readValue = analogRead(sensorIn);
if (readValue > maxValue)
{
maxValue = readValue;
}
if (readValue < minValue)
{
minValue = readValue;
}
}
result = ((maxValue - minValue) * mcuVoltage) / 1024.0;
return result;
}
// V0 AC IRMS display
// V1 WH display
BLYNK_WRITE(V2) { // calibration slider 50 to 70
calibration = param.asInt();
}
// V3 WH gauge
BLYNK_WRITE(V4) { // set supply voltage slider 70 to 260
inputV = param.asInt();
}
BLYNK_WRITE(V5) { // set 5, 20 or 30A ACS712 with menu
switch (param.asInt())
{
case 1: { // 30A
mVperAmp = 66;
break;
}
case 2: { // 20A
mVperAmp = 100;
break;
}
case 3: { // 5A
mVperAmp = 185;
break;
}
default: { // 30A
mVperAmp = 66;
}
}
}
// V6 Cost gauge
BLYNK_WRITE(V7) { // PF slider 60 to 100 i.e 0.60 to 1.00, default 95
pF = param.asInt();
}
BLYNK_WRITE(V8) { // Energy tariff slider 1000 to 2000, default 1437 (UK £ 0.1437 / KWH)
energyTariff = param.asInt();
}
BLYNK_WRITE(V16){
CumumlativeCostToday = param.asFloat();
}
/*void GetUpdates() {
t2secCost2 = ((WH / 1000.0) * energyTariff ) * ( 2 / 3600);//
CumumlativeCostToday = CumumlativeCostToday + t2secCost; //
Blynk.virtualWrite(V16, CumumlativeCostToday);
}*/
void setup() {
WiFi.hostname(myhostname);
Serial.begin(115200);
Serial.println("\n Rebooted");
WiFi.mode(WIFI_STA);
#ifdef CLOUD
Blynk.begin(auth, ssid, pass);
#else
Blynk.begin(auth, ssid, pass, server);
#endif
while (Blynk.connect() == false) {}
ArduinoOTA.setHostname(myhostname);
ArduinoOTA.begin();
timer.setInterval(2000L, getACS712); // get data every 2s
//timer.setInterval(5000L, GetUpdates);
}
BLYNK_CONNECTED(){
Blynk.syncVirtual(16);
}
void loop() {
Blynk.run();
ArduinoOTA.handle();
timer.run();
}
I changed accordingly
but no result except 0.0 on v16
I said lots of decimal places, 2 is not lots.
Values are very, very small for cost over 2s. Try this:
Serial.println(String(energyCostpermonth, 6));
Serial.println(String(CumumlativeCostToday, 6));
Blynk.virtualWrite(V6, String(energyCostpermonth, 6));
Blynk.virtualWrite(V16, String(CumumlativeCostToday, 6));
I did as you showed and no results, just 0.000000, also put 8 up to 10 instead of 6
Maybe you are mixing up the floats and ints. Do a Serial.println() after every calculation to pick out the bugs.
should I change these
float CumumlativeCostToday = 0;
float t2secCost = 0;
to int?
Serial.println(String(CumumlativeCostToday, 10));
just : 0.0000000000 s
No, these numbers are tiny and must be floats. Probably some of your ints should be floats.
Is this the first Serial.println() that shows zero as you work down the function?
can you able to point it out?
0.732 Amps RMS Power: 165.405 WH Approx cost per month: Tg2500.9250488281
0.0000000000
0.713 Amps RMS Power: 161.186 WH Approx cost per month: Tg2437.1320800781
0.0000000000
0.704 Amps RMS Power: 159.076 WH Approx cost per month: Tg2405.2360839844
0.0000000000
0.713 Amps RMS Power: 161.186 WH Approx cost per month: Tg2437.1320800781
0.0000000000
I want to see:
calc 1
serial print
calc 2
serial print
calc 3
serial print
Not a loop of a single serial print. You need say 5 or 6 more serial prints in the function.
I will need to know which calc gives each serial print output.
Also try changing 3600 to 3600.0.
it worked thank you 