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Kettle on Gas vs Electric Kettle

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  • Spies said:
    The half hour reading on my Gas smart meter has updated so we have results.

    500ml of cold water, enough for 2 cups of tea took 5 minutes to boil on the gas stove, that was using a small milk pan with a lid over the top, this used 0.17kWh of gas, costing 0.68p

    The same test using an electric kettle, which ran at ~2800w for 1 minute 24 seconds, used 0.0715kWh of electricity at a cost of 1.43p



    Around half price.  When I ran mine (5 years ago) I was saving around a penny a boil.
  • Spies
    Spies Posts: 2,267 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    edited 19 January 2022 at 12:54AM
    We must boil the kettle around 12 times a day I would guess, that's (almost) 10p saving per day if I was to get a stovetop kettle.

    It would pay for itself in 100 days  :D:o
    4.29kWp Solar system, 45/55 South/West split in cloudy rainy Cumbria. 
  • Spies said:
    We must boil the kettle around 12 times a day I would guess, that's (almost) 10p saving per day if I was to get a stovetop kettle.

    It would pay for itself in 100 days  :D:o

    Yes, when I worked out the savings - I bought a stove kettle.  I still have my electric kettle, which is used when boiling water for cooking - otherwise, stove kettle is used.  I love the whistle.
  • Petriix
    Petriix Posts: 2,296 Forumite
    Ninth Anniversary 1,000 Posts Photogenic Name Dropper
    We already had a stove top kettle for camping, so it was no extra expense. However we also have solar panels which can contribute to the electric kettle boiling. It turns choosing which kettle to boil into a complex exercise.

    One significant factor is that, in winter, the wasted gas provides useful heat, which coincides nicely with the lack of sunshine. In practice we tend to only run the electric kettle when at least 66% of the energy comes from solar.

    We're soon having a battery installed which will allow us to boil the electric kettle at the overnight rate of 5p per kWh (plus round trip losses). With the expected gas price rise in April I suspect we'll switch to using the electric kettle all the time.
  • jrawle
    jrawle Posts: 619 Forumite
    Part of the Furniture 500 Posts Name Dropper
    Spies said:
    The half hour reading on my Gas smart meter has updated so we have results.

    These workings are based on unit prices of 20p/kWh for Electricity and 4p/kWh for Gas.

    500ml of cold water, enough for 2 cups of tea took 5 minutes to boil on the gas stove, that was using a small milk pan with a lid over the top, this used 0.17kWh of gas, costing 0.68p

    The same test using an electric kettle, which ran at ~2800w for 1 minute 24 seconds, used 0.0715kWh of electricity at a cost of 1.43p



    Thanks for doing this test. It suggests ~40% efficiency for gas as some posters estimated.

    I wondered, though, how people light their gas hobs. If you have electric ignition, the cost will be negligible, but if you use matches, it probably wipes out the cost saving.
  • Spies
    Spies Posts: 2,267 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    jrawle said:
    Spies said:
    The half hour reading on my Gas smart meter has updated so we have results.

    These workings are based on unit prices of 20p/kWh for Electricity and 4p/kWh for Gas.

    500ml of cold water, enough for 2 cups of tea took 5 minutes to boil on the gas stove, that was using a small milk pan with a lid over the top, this used 0.17kWh of gas, costing 0.68p

    The same test using an electric kettle, which ran at ~2800w for 1 minute 24 seconds, used 0.0715kWh of electricity at a cost of 1.43p



    Thanks for doing this test. It suggests ~40% efficiency for gas as some posters estimated.

    I wondered, though, how people light their gas hobs. If you have electric ignition, the cost will be negligible, but if you use matches, it probably wipes out the cost saving.
    electric ignition will be miniscule, its literally a spark.
    4.29kWp Solar system, 45/55 South/West split in cloudy rainy Cumbria. 
  • Sandtree
    Sandtree Posts: 10,628 Forumite
    10,000 Posts Fourth Anniversary Name Dropper
    jrawle said:
    Spies said:
    The half hour reading on my Gas smart meter has updated so we have results.

    These workings are based on unit prices of 20p/kWh for Electricity and 4p/kWh for Gas.

    500ml of cold water, enough for 2 cups of tea took 5 minutes to boil on the gas stove, that was using a small milk pan with a lid over the top, this used 0.17kWh of gas, costing 0.68p

    The same test using an electric kettle, which ran at ~2800w for 1 minute 24 seconds, used 0.0715kWh of electricity at a cost of 1.43p



    Thanks for doing this test. It suggests ~40% efficiency for gas as some posters estimated.

    I wondered, though, how people light their gas hobs. If you have electric ignition, the cost will be negligible, but if you use matches, it probably wipes out the cost saving.
    The bigger thing is the ratio of electricity and gas prices... if you've come out of fixed period for gas and now paying the 10p rather than 4p then your worse off using the hob based on the energy use estimates above
  • Spies
    Spies Posts: 2,267 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    Both fuels are likely to go up the same amount, 50%, making unit prices 30p and 6p respectively, so it should still be the same ratio.
    4.29kWp Solar system, 45/55 South/West split in cloudy rainy Cumbria. 
  • PennineAcute
    PennineAcute Posts: 1,185 Forumite
    Eighth Anniversary 1,000 Posts Name Dropper
    My new fix is 5.48p and 22.36p  

    ALthough I ran my test many years ago, using the figures from Spies.

    .009316p for gas.  So around a penny.

    0.39182 for elec.  So around 4p.   3p saving.

    I note that Spies boiled water for 2.  I boil water for 1, so around 1.5p saving, which it approximately what I got back in 2017. 

    I work from home for most of the time.  Kettle is on around 15 times a day. So about 22p a day saving, which equates to £80 a year saving.

    I have switched supplier to save less than £80.

    When I installed by combi shower, I again noticed a saving.

    I used on average 1 kWh with my electric shower.  Today's cost 22.36p

    With my combi, I use on average 2.3 kWh of gas.  Today's cost 12.604p    Saving 9.756p.  Annual saving £35.61

    Total annual savings £115 switching from electricity to gas.
  • jrawle
    jrawle Posts: 619 Forumite
    Part of the Furniture 500 Posts Name Dropper
    Spies said:
    The half hour reading on my Gas smart meter has updated so we have results.

    These workings are based on unit prices of 20p/kWh for Electricity and 4p/kWh for Gas.

    500ml of cold water, enough for 2 cups of tea took 5 minutes to boil on the gas stove, that was using a small milk pan with a lid over the top, this used 0.17kWh of gas, costing 0.68p

    The same test using an electric kettle, which ran at ~2800w for 1 minute 24 seconds, used 0.0715kWh of electricity at a cost of 1.43p


    Looking at the figures again, if the electricity usage is accurate, that suggests the electric kettle is only 75% efficient.

    The theoretical value for a 100% efficient kettle:
    Energy used = 0.5 x 4200 x 90 = 189 kJ = 0.0525 kWh
    (mass of water = 0.5 kg, specific heat capacity of water = 4200 J/kg/K, temperature difference 90K assuming water starts at 10°C, makes little difference if you use 100)

    That means the hob is only 30% efficient. Of course, this makes no difference to this discussion as the relative efficiencies are the same. I'm just commenting for interest's sake as many people, including myself, often claim that electric water heating is nearly 100% efficient.
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