Jump to content

How much it costs to run X watt device for Y minutes?


Recommended Posts

The above calculation is correct , but 1 remark .

If it is a engine , like for example a pressure washer , pump , vacuumcleaner , ...  Every time it starts , power consumption is way higher , 2-3 times the value . It might be only a brief second , but it is the biggest difference why inverter things ( airco .. ) use less electricity then the standard ones .

Link to post
Share on other sites

How much it costs to run X watt device for Y minutes?

 X x Y x unit rate / 60,000 b., where unit rate is baht cost per KWH.

 

robblok is correct. I just give the general formula.

 

sezze I dont think is correct. The cost of a 1000 watt device running for 1 sec. at a 5b. unit rate is 0.14 satang. So even a 3-times increase in starting load is is less than half satang. So you would have to have to start/stop 200 times a day for it to cost 1b.

  • Like 2
Link to post
Share on other sites
6 hours ago, Why Me said:

How much it costs to run X watt device for Y minutes?

 X x Y x unit rate / 60,000 b., where unit rate is baht cost per KWH.

 

robblok is correct. I just give the general formula.

 

sezze I dont think is correct. The cost of a 1000 watt device running for 1 sec. at a 5b. unit rate is 0.14 satang. So even a 3-times increase in starting load is is less than half satang. So you would have to have to start/stop 200 times a day for it to cost 1b.

It depends on the load and how many times it starts and stops . This comes above the normal running costs , and yes it might not be a lot for a single this , like a 1000watt thing doesn't matter running 20 mins , but doing it 24/7 , 4 times per hour , is 2880 times , during 3 seconds equals 2h20 mins at double power ( 2000watt extra ) or in consumption

about 5kwh extra . It really is the difference between inverters and non inverters . The amount of power running something stays the same , for example the aircon needs x amount of cooling to keep that temperature . The inverter chooses it's power needed and keeps the compressor running , but maybe at 1/4th of total power while the other 1 starts and stops , making bigger consumption in total needed .

  • Like 1
Link to post
Share on other sites
12 hours ago, sezze said:

The above calculation is correct , but 1 remark .

If it is a engine , like for example a pressure washer , pump , vacuumcleaner , ...  Every time it starts , power consumption is way higher , 2-3 times the value . It might be only a brief second , but it is the biggest difference why inverter things ( airco .. ) use less electricity then the standard ones .

The standard induction motor, which are the majority of motors takes 6 times full load current at the instant of starting. This is just the nature of the beast. However this is for a very short time. Most devices around the house are not stopped started that many times in an hour, even water pump.

 

My first house I rented in Thailand the water pump was obviously too big for the size of the piping. When the kitchen tap was used the pump would stop/start every couple of seconds. Very annoying as it also sent a "bang" through the stainless tank. I played around with throttling the water inlet and problem fixed.

 

I used to work in a power station with 500 megawatt units. Each unit had 3 boiler feed water pumps with a rating of 9000 hp at 11,000 volts. Full load current was 6.7 megawatts so you can imaging at the instant of starting the amount of power used. As we were the source of power no starting devices were employed it was just DOL (direct on line). Lights dimmed at the power station.

 

Really it doesn't make much difference in home use as the relatively cheap metering will not measure the full staring current as it happens too fast for the instrument to measure accurately. Power Factor also is a component but will not attempt to explain pf. Inverter ACs have a lot of capacitors improving the pf.

Edited by Dazinoz
  • Thanks 1
Link to post
Share on other sites
13 hours ago, robblok said:

(1.2 x 4.7 x 20) / 60 = 1.88 bt

 

That is assuming im correct that a KWH is 4.7 bt. I thought it ro

13 hours ago, sezze said:

The above calculation is correct , but 1 remark .

If it is a engine , like for example a pressure washer , pump , vacuumcleaner , ...  Every time it starts , power consumption is way higher , 2-3 times the value . It might be only a brief second , but it is the biggest difference why inverter things ( airco .. ) use less electricity then the standard ones .

This brief second is referred to as the "surge" in electricity

Edited by Percy P
Link to post
Share on other sites
14 hours ago, robblok said:

(1.2 x 4.7 x 20) / 60 = 1.88 bt

 

That is assuming im correct that a KWH is 4.7 bt. I thought it roughly was.

 

The government price per kwh is just 4 baht + 7% tax = 4,28 baht.  That's what I'm paying to PEA. A lot of people pay 8 baht or even more which is a rip off. 

Link to post
Share on other sites
1 hour ago, scoupeo said:

can someone help to calculate 24h aircon sot for 18000 btu ?

thank you.

 

 

A reasonably modern conventional A/C of 18k BTU will swallow about 1.8kW when the compressor is running.

 

If it's correctly sized count on a duty-cycle of about 30%.

 

So each hour of operation would be 1.8 * .3  = 0.54 kWh.

Link to post
Share on other sites
16 hours ago, robblok said:

(1.2 x 4.7 x 20) / 60 = 1.88 bt

 

That is assuming im correct that a KWH is 4.7 bt. I thought it roughly was.

 

or 1.2 x4.7 / 3 = 1,88 baht

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...