# Calculating Energy Waste of Making 4 Coffee Cups/Day

• suf7
In summary, a man wastes energy every time he makes his coffee by heating more water than necessary. The amount of energy wasted can be estimated by calculating the energy required to raise the temperature of the unused water from room temperature to boiling. With reasonable assumptions, this amount can be determined to be approximately 900 million joules per year. To calculate the cost of this energy, further research and data from a reliable source is needed.
suf7
HI I am really stuck with this question, i don't know what to do with it??..can anyone help??..id like to learn how to solve this question...thanks.

A man makes two cups of instant coffee four times a day. On every occasion he fills the kettle up to the 10-cup level. What is the cost of the energy he wastes in one year by heating more water than is neccessary??..make suitable assumptions to solve.

Pleeeeeeeeeez help me!

Last edited:
Every time he makes his coffee the man "wastes" the energy required to heat the 8 cups of water he doesn't use. How much energy does it take to raise the temperature of 8 cups of water from room temperature to boiling?

Doc Al said:
Every time he makes his coffee the man "wastes" the energy required to heat the 8 cups of water he doesn't use. How much energy does it take to raise the temperature of 8 cups of water from room temperature to boiling?

i don't know how to work it out??...what formula should i use??

Doc Al said:
Every time he makes his coffee the man "wastes" the energy required to heat the 8 cups of water he doesn't use. How much energy does it take to raise the temperature of 8 cups of water from room temperature to boiling?

Is this the formula??...

Energy = M x C x Change in temperature

Room temp is roughly 15 C
Boiling temp = 100 C

So change in temp = 85 C

C, specific heat capacity for water = 4190

Not sure about "M" if this is the right formula?

All of this is quite reasonable. (Note: 15 degrees C = 59 degrees F) Take care to use proper units. The specific heat of water is in J/kg. To find M: What is the mass of a cup of water?

When you put it all together, you'll need to figure how many (unnecessary) cups of water the man heats in a year.

Doc Al said:
All of this is quite reasonable. (Note: 15 degrees C = 59 degrees F) Take care to use proper units. The specific heat of water is in J/kg. To find M: What is the mass of a cup of water?

When you put it all together, you'll need to figure how many (unnecessary) cups of water the man heats in a year.

Thanks...but i don't know how to work out the mass of a cup of water??

Come on... don't be lazy! How many ounces in that coffee cup? (Make a reasonable assumption!) 1 fluid ounce is about 30 cm^3; the density of water is 1 gram per cm^3.

Doc Al said:
Come on... don't be lazy! How many ounces in that coffee cup? (Make a reasonable assumption!) 1 fluid ounce is about 30 cm^3; the density of water is 1 gram per cm^3.

so should i get a cup and measure its weight, then fill it with water and measure the weight again, subtract one from the other and il have the mass of water??..then i should convert the value accordingly??

Why go to all that trouble? (Though you can if you have a scale handy!)

Just guess as to how many ounces of water in each cup! (1 standard cup = 8 fluid oz.) Then use the data I provided to find the mass (in kg) of that cup of water.

Doc Al said:
Why go to all that trouble? (Though you can if you have a scale handy!)

Just guess as to how many ounces of water in each cup! (1 standard cup = 8 fluid oz.) Then use the data I provided to find the mass (in kg) of that cup of water.

ok so does that mean that the mass of water per cup works out at 0.24kg so the amount of water being wasted evrytime he makes his 2cups is:
E = M x C x CIT
= 1.92 x 4190 x 78
= 627494.4 j (This is for ONE boiling of the kettle)

so that means that in a day the energy being wasted is 2,509,977.6 j

so in a year would be 2,509,977.6 j x 365 = 916,141,824 j

does that seem correct?

Sounds good to me. It looks like you changed your assumption about the temperature difference from 85 degrees to 78 degrees. But no matter; the point is to give a reasonable estimation of the energy wasted. Since we're just estimating anyway, I'd round off that final answer. Given your assumptions, the energy wasted is approximately 900 million joules per year! (If you stuck with your first assumption -- 85 degree change -- the answer would be about 1 billion joules.)

Doc Al said:
Sounds good to me. It looks like you changed your assumption about the temperature difference from 85 degrees to 78 degrees. But no matter; the point is to give a reasonable estimation of the energy wasted. Since we're just estimating anyway, I'd round off that final answer. Given your assumptions, the energy wasted is approximately 900 million joules per year! (If you stuck with your first assumption -- 85 degree change -- the answer would be about 1 billion joules.)

wow, it actually looks right??..thanks for your help..so for the final part how would i work out the cost of that energy?..??..i went to the npower website to find out some figures but its all so confusing??

## 1. How is energy waste calculated when making 4 coffee cups per day?

To calculate energy waste, you need to determine the energy consumption of each step in making 4 coffee cups per day. This includes the energy used to boil water, run the coffee maker, and heat milk if applicable. Once you have the energy consumption for each step, you can add them together to get the total energy waste.

## 2. What is the average amount of energy wasted when making 4 coffee cups per day?

The average amount of energy wasted when making 4 coffee cups per day depends on the type of coffee maker, the energy efficiency of the appliances used, and the energy source (e.g. electricity, gas). It is best to calculate the specific energy waste for your own coffee-making routine.

## 3. How can I reduce energy waste when making 4 coffee cups per day?

There are several ways to reduce energy waste when making 4 coffee cups per day. One way is to use energy-efficient appliances, such as a coffee maker with an automatic shut-off feature. Another way is to use renewable energy sources, such as solar or wind power, to power your coffee-making routine. You can also reduce energy waste by only boiling the amount of water you need and turning off appliances when not in use.

## 4. Does the type of coffee affect the energy waste when making 4 coffee cups per day?

The type of coffee used may affect the energy waste in terms of the energy needed to roast and grind the beans. However, the biggest factor in energy waste when making 4 coffee cups per day is the energy consumption of the appliances and the amount of water used.

## 5. How does the energy waste of making 4 coffee cups per day impact the environment?

The energy waste of making 4 coffee cups per day can have a significant impact on the environment. The production of energy often involves burning fossil fuels, which contributes to air pollution and climate change. By reducing energy waste, we can help mitigate these negative impacts on the environment.

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