Kettle vs Hob Energy: Cost per Cup and per Litre

Boiling water is something we do every day with home appliances. The good news is, small changes can help a lot with heating water and cut down on energy bills, since this is what uses most of the energy. This easy-to-read guide looks at how well an electric tea kettle works when you compare it to an induction hob, electric (ceramic) hob, and gas hob. You will see clear numbers for kilowatt hours. There are tables for litres of water and cups of water. You will also find tips about using less water, shortening boiling time, and saving on energy bills. There are simple notes about instant hot water taps and kettle design too.

Why boiling water costs what it does (and how to estimate it)

Heating water takes a fixed amount of energy:

• The thermal energy needed to heat room-temperature cold water (about 20 °C) up to the boiling point (100 °C at sea level) is about 0.093 kWh per litre.
• The wall energy used is equal to the thermal energy divided by the efficiency of the method. Some heat will come out into the surrounding air as heat loss.
• The cost (£) is equal to kWh times your cost of electricity (in p/kWh divided by 100). For gas, use the same kWh formula with your gas price.

Air pressure has a big role in cooking. At places that are higher up, the boiling point goes down. At sea level water boils at 100 °C, which is 212 degrees Fahrenheit. In most UK areas, this change is very small. Still, this helps to show why a watched pot may need more time to boil in the mountains.

Typical real-world efficiencies

• Electric kettle: ~85–95% (the heating part goes in the water. Not much heat goes to the room)
• Induction hob: ~80–90% (a magnet connects right to the pan. ).
• Electric ceramic hob: ~60–75% (it warms up the glass first).
• Gas hob: ~35–50% (a flame gives heat around the pan of water).

Quick reference: kWh to boil 1 litre by method

Using these middle-level numbers for how well each works (kettle 90%, induction 85%, ceramic 70%, gas 40%):

Cost tables you can plug your tariff into

Replace unit rates with your own if they are not the same. The numbers shown are in £.

Electric methods (kettles and electric hobs)

Assumed electricity rates: 18p, 28p, 38p per kWh.

(“£0.00” means <1p when rounded.)

Gas hob (natural gas)

Assumed gas rates: 6p, 8p, 10p per kWh.

Because gas is usually less costly for each kWh than electricity, a gas hob can still be a good choice for big pots. It may use more energy because there is heat loss around the pan, but the lower cost can help.

Kettle vs hob: which is faster to the boil?

Typical boiling time to reach a rolling boil from room temperature for 1 litre:

• 3 kW electric kettle: It takes about 2–3 minutes. This is the fastest way because the heating element is right in the water.
• Induction hob (1.8–2.0 kW zone, use a lidded stainless steel or layered pan): It takes about 3–4 minutes.
• Gas hob (medium–high burner, with a lid): It takes about 4–6 minutes.
• Electric ceramic hob (with a lid): It takes about 5–7 minutes.

A flat and wide pan base lets the heat reach all parts of the pan. A tight lid keeps the heat inside. The burner, when it matches the size of the pan, helps the heat go into the water molecules and not out into the room.

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“Boil only what you need” isn’t a cliché—here’s the maths

If tea drinkers use a full kettle (about 1.5 to 1.7 liters) to make two cups of tea (around 500 milliliters), about two-thirds of the energy becomes water vapor or cools off in the jug. This is just energy waste. The minimum fill line is there for a good reason—to keep the element safe. But if you fill the kettle with just enough water for one cup, just above the minimum fill, you get your cup of water and save money each day.

Quick test: Start by filling your mug with cold water. Then, pour it into the kettle. This sets the water level just right. Boil the kettle. When the kettle boils, you will have the exact amount you need for hot drinks.

Variable-temperature kettles and specific temperature brewing

Many efficient kettles in modern kitchens come with temperature control. These let you choose a specific temperature, like 80 °C, 90 °C, or 95 °C (176/194/203 °F). If you want to make green tea at 80 °C, you can save about 25% compared to first boiling the water to 100 °C and then waiting for it to cool down. This way, the boiling time is less because the temperature of the water does not need to get so high.

Kettle design: what actually makes one “efficient”?

• Concealed heating element: This makes it easier to clean. It also helps stop thick limescale from building up. The way heat moves stays good.
• Double-wall or vacuum insulation: This lowers heat loss to the surrounding air. So, your hot water stays warm for a longer time. You will not need to boil it again often.
• Accurate thermostat & auto-off: It stops the hot water from getting too hot. This means you will not pass the set temperature.
• Clear water level window: You can see how much water is inside. This helps you avoid putting in too much water by mistake.
• Materials: A stainless steel jug is strong and lasts a long time. A plastic jug also keeps hot water warm well. The insulation is what makes the biggest difference, not just the material.

Maintenance for low energy use

• Descale the kettle every few weeks if you live in a hard water area. You can use white vinegar or citric acid for this. Scale will make the boiling time longer because it covers the element.
• Rinse the kettle after you descale it. This helps to keep the taste good.
• Don’t use the kettle when the water is below the minimum fill mark. If you do, the dry-boil protection can trip, and it might hurt the element.

Instant hot water taps: convenience vs standby

“Instant hot water” systems like under-sink boilers or dispensers can give you hot water fast. You just need to turn them on, and there will be near-boiling water whenever you want it. Think about this if you want hot water to be ready all the time. These units will help you save time and make things easier in your kitchen by giving you instant hot water when you need it.

• You will have to pay more upfront costs for one than you do for a kettle.
• A small tank uses standby energy to stay hot. Good models have strong insulation, but poor insulation causes a steady form of heat loss.
• If your household makes many cups of tea every hour, it is very convenient to use. But for regular use when you only want a cup or two now and then, a kettle will be more efficient. A kettle heats only what you need at that time.

Hob choices: induction, ceramic electric, or gas?

• Induction hob: this be a good way for heating water. The hob sends energy to the pan through magnets, so most of the amount of power gets to the water. It works well for small pans and is great when you heat water to cook pasta in the first place.
• Electric ceramic hob: this type be slower and some heat leaks away. Always use a lid and make sure the ring fits the pan.
• Gas hob: this is very quick to change heat. The flame heats your pan of water fast, but some heat goes out and warms the room instead of the water. If you use natural gas, the total cost can still be low for big pots.

Worked examples you can adapt

One cup of tea (250 ml) from 20 °C to 100 °C

• Kettle @ 90%: It uses about 0.026 kWh. That costs about 1p when the price is 28p for each kWh.
• Induction @ 85%: It uses about 0.027 kWh. That also comes to around 1p.
• Gas @ 40%: It uses about 0.058 kWh. That costs about 0.6p when gas is 10p for each kWh.

Four cups of water (1.0 L) for pasta

• Kettle pre-boil then induction simmer helps you save both time and power, compared to starting with a full cold litre on a ceramic hob.
• When you cook a lot of food (like a 3 L stockpot), it is better to use the hob from the start. Moving boiling water from the kettle to the pot several times just adds extra work. It does not really save energy.

Where does the electricity come from?

Your plug power comes from the grid. In the UK, this means a mix of energy sources. These are wind, solar, nuclear, and gas-fired power station generation. The mix does not change the cost of electricity that you pay each kWh today. But, it does help to explain why electricity and gas can have different unit prices over time. If your bill still feels high even when you have good habits, it is a good idea to take a minute to compare energy prices.

Troubleshooting higher-than-expected kettle costs

• Boiling a full kettle for just one mug? Set the water level by filling your mug first, then pour it into the kettle.
• If you keep re-boiling water, use temperature control. A thermos will keep any extra hot so you don’t need to boil it again.
• If you see scale building up, clean your kettle with white vinegar. A scaled element means the boiling time goes up.
• A warped pan on induction does not touch the surface well, so the energy consumption goes up.
• If you don’t keep a lid on the pot, steam will get out. That loss is visible energy waste right in front of you.

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Kettle vs Hob Energy: practical takeaways

• If you want to make one or two mugs, the electric tea kettle or the induction hob is usually the cheapest way to do it.
• If you have bigger pans or you are cooking more, induction or gas can be easier to use. With natural gas, the price for each unit might help make up for its lower efficiency when you heat large amounts.
• The amount of water always matters most: just heat what you will use.
• If energy prices are still too high, an easy fix is to compare energy prices and try to lower the rate you pay for each kWh.

FAQs About Kettle vs Hob Energy