Electricity Usage

  1. druist Member

    Posts: 28
    Is there an equation or does anyone have a rough idea of how much a 135w mig welder would use in terms of KW/h for say 5mins use?

    I am trying to estimate the cost of using a DIY mig welder at home. Just curious if anyone has anyone tried to do this calculation?


    Last edited: Nov 20, 2007
  2. peterd51

    peterd51 happy to be here!


    it's a 'hobby' I use it and ****** to the cost! :-)

    I'd say it'll run at a few pence an hour though I've never really checked.

  3. I run (well did) a 250amp machine which spent most of its time set at 220-230amps, used daily in the fabrication of gates, at that sort of power output its drawing about 6kw, which would mean at the current cost of electricity (about 10pence per KWh) in an hour would cost 60 pence, but it never runs for a full hour. I recon it probaly costs about £5 a week to power it.

    In the Lorch book of welding there is an interesting bit about what does 1mtr of welding cost. If lorch's figures are correct and i have no reason to doubt them. they claim 76% is the cost of the labour, 9% is the cost of the gas, 4% is the cost of the electric, 6% is the cost of the wire, and 5% is the cost of the welding unit.
    So in reality if everytime you replace a roll of wire (i assume you use the baby rolls) and it cost you £10 i would guess you have used no more than £5 worth of electricity.
    Does that help?
  4. Hello Drew,

    the equation is 135/1000 x 1Hr Kwh. However as you welding current varies so does the load, i.e. 135watts will often be much less. How much will need a meter to measure your current drawn from the mains. Wattage is volts x amps x power factor (Usually around 0.8)

    Not easy to know without some test equipment

  5. greyshirtguy

    greyshirtguy Persistent Learner

    Cost Estimation

    hmmm I have wondered about that too - it's probably too hard to guess how all the variables will come out without actually measuring (I even had a few fleeting ideas of current meters etc - yer, I'm a nerd)

    Although, I'd say the cost of the electricity is quite small (as IronDarren pointed out 4%)...

    Consider these two points:

    1. Calculate the max your welder could possibly use and know that it's typical usage will be less than that.
    Take your supply voltage and multiply by the Max current your circuit (fuse/breaker) can supply to your welder. That should tell you the maximum possible power it can use. Decide how many hours you use your welder for and multiply out to get your total energy usage. Multiply by your current electricity tarrif rate.
    eg. Mine is supply is 240V, through a 16amp breaker
    240x16 = 3.84KW
    My Tarrif is apporx 15c per KWh...
    So if my welder max's out my circuit it could use up to 57.6cents per hour.

    2. If you really want to get an idea of how much power each setting uses you could......take some "before" and "after" readings from your power meter, and note the number of KWs used during test welds at given settings, wire speed/size.
    Hmmm, actually This might not be a very smart option at all !!!! - since it seems that would take at least 1 hour of continous welding for my meter to read an extra 3.84KWh's...hmmm My meter also has a "spinning wheel" that would indicate much smaller amounts of consumed power - but you'd have to count the revs....wonder what the wife would say? ;)
  6. peterd51

    peterd51 happy to be here!


    yes, especially when you insist on turning off all other electrical items while testing...

  7. Drains

    Drains Yeah, nah.

    Posts: 7,691
    Sefton, South Island, NZ
    I'm not convinced thats Drew's welder is 135 watts. You'll not do much welding at that. Did you mean amps Drew?

    Greyshirtguy explains it all nicely.
  8. Hello GSG,

    you haven't quite got it right. The breaker current merely gives the maximum available current, what you need is the draw from the welder which is variable. Also you need to consider the power factor in your calculation, volts times amps is not watts with A.C. (it is with D.C. normally)


    yes, 135 watts is quite light, maybe it is the output current as you say, but certainly not input current.

  9. peterd51

    peterd51 happy to be here!


    I think the 1st line of GSG's item 1 covered it...

    'Calculate the max your welder could possibly use and know that it's typical usage will be less than that'

    A few pence an hour is the maximum...for DIY use it'll be a few pence a day in actual use.

  10. Hi
    135w is 0.135kw to start off with. this is very low and I have a bigger soldering iron.
    this will run a few cooling fans but will not melt metal.
    you probably mean 135A as this is a bobby welder
    the wattage you are using is calculated volts x Amps = Watts
    1000 watts = 1KW
    and costs depending on supplyer 7p per hr.

    the voltage you are using should be on the plate near the the power lead and this is known as an open circuit voltage probably about 28v if it is 135A you are not going you are going to struggle running the power flat out so you may manage 125A as this is dependant on wire dia and speed and cheaper sets strugle to give the power they say.

    28V x 125A = 3500W = 3.5kW this is if you are pushing your set at full power with a good ark.

    if you are fabricating you are welding a max of 5% of the time.
    if you are doing production fabrications you are welding maximum 25% of the time.
    if you are plating you are Welding a max of 40% of the time and your set will be dead after about 200hrs as it is not made for this.

    so if you are fabricating like I would expect there is a maximum of 5% of the time welding more realistically 2.5% as you are not doing it proffesionally.

    3.5kw x .025 gives you 0.0875 kW at a cost of 7p ish a kw meaning it will cost you .6125p per hr.

    I have you an important question how many lights do you have because these will cost more.

    the lights in my old workshop used to use approx 8kw and this was the most expensive electricity cost on the workshop.

    yes a welder will make your elecrtic meter go dizzy but only whist it is running. but so will your kettle as this uses about the same power and runns about the same length of time.

    dont bother aboth the power you welder uses.

  11. Hello Pete,

    what on earth have you installed as lighting, 8Kw? 16 x 500 watt Halogens would give that, how big is your workshop. Fluorescents are much better and far less power.

    Your wattage calculation is wrong, by the way, see a couple of my earlier posts.

  12. malcolm

    malcolm Bob the builder

    Posts: 8,385
    Bedford UK
    I once rented a workshop from a bloke who complained about how much electricity I was using with the MIG. I pointed out I was on a 13 amp fuse and my welding speed is maybe 1m in 6 minutes, and I wasn't doing more than 1m of welding each day.

    Turned out it was the striplights he'd installed to grow cannabis plants (on 24 hours a day) that were eating the electricity.
  13. My workshop was 15,000 sq ft it had about 14 450w Highbay lights and lots of florecent lights at least 30 around machines and major work areas
  14. Hello T and T,

    not quite the sort of workshop I was imagining. However, lighting is normally a small part of the total load of most establishments, but of course depends on what machinery and duty cycles they have. The last place I worked at, although exceptional, had in one small part of the factory two motors, one 6,000 Kw and a smaller 4,000 Kw, (and that is not a misprint)

  15. druist Member

    Posts: 28

    AAAHHHHGGG. Sorry guys bit of an error there I meant AMPS. I havent got it yet its either going to be the

    Clarke MIG 135TE 130 amp MIG135TE or the

    Sealey S0771 Mini MIG Welder 130Amp 230V S0771

    Why it concerns me is that our electric bill has doubles its about 12p per KWh. (22cents roughly.)
  16. Hello Drew,

    think of it this way, weld for about 20 hours continuously or buy one pint of beer?

  17. Ill do some serius maths here, for anyone that is worried about the electricity use.

    ill assume you (on anyone is using 0.8mm wire and flatout 130amps)

    at 130 amps the wire feed should be 5mtrs per minute. one cubic cm of steel weighs 8gms.
    5mtrs (500cm) of wire is 500 x (0.04 x 0.04 x3.141) = 2.51 cm3 (radius square times Pi = area) (area x height/lenth = volume)
    2.51 x 8 grams = 20 grams. so 1 mins welding uses 20 grams of welding wire. the baby reels are 0.7kg or 700 grams, so 700grams divided by 20 grams = 35 or 35 minutes worth of welding from a baby reel. Ill assume that at 130 amps the machine draws 3kw, truth is more like 2.2kw.
    35mins/60mins = 0.58333 of an hour. 0.583333 x 3kw = 1.75kwh. at todays prices of about 12 pence per kw that around 21pence for every 700grams of wire laided down.

    if you run a 5kg reel, then its about £1.50 per roll or a 15kg reel is £4.50 a roll. obviously if your running at lower power or higher power than 130amps the price will differ slightly

    check my calculations they might be wrong, but hopefully that clears the cost of welding up
  18. burntmebonce

    burntmebonce 999 on speed dial

    Posts: 47
    ah i dont worry about what power i am using in my workshop but on the other hand the couple next door they are sure i have hooked on to his electric supply as every time i strike an arc the lights flicker in her kitchen:confused:
    and not in my house Ha Ha (no i aint wired in to the wrong house):hug:
  19. I am lost with some of the views that have recently been put on this thread

    "if you run a 5kg reel, then its about £1.50 per roll or a 15kg reel is £4.50 a roll. obviously if your running at lower power or higher power than 130amps the price will differ slightly"


    think of it this way, weld for about 20 hours continuously or buy one pint of beer?

    I spent a few weeks doing some heavy plating and I was using an 18 kg roll of wire in about 5 hrs does this mean it costs over £18 to buy a pint of beer??

    I have even used more than 15kg in 8hrs on production welds on 4mm thick components.

  20. Hello Pete,

    you are getting confused over the original point which is electrical cost of welding.

    The beer comment was 12p per hour so 20 hours = 240 p about the price of a decent pint.

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