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9.01 Interpreting household bills

Worksheet
Usage
1

An electricity company charges \$0.175 per \text{kWh}. Based on the data below, calculate the household's electricity bill cost for the entire season of Spring.

\text{Usage per day (kWh)}\text{Usage for time period (kWh)}
Summer16.41495
Autumn17.41589
Winter19.51776
Spring19.31757
Year18.16617
2

An electricity company charges \$0.185 per \text{kWh}. Based on the data below, calculate the household's electricity bill cost for the entire year.

\text{Usage per day (kWh)}\text{Usage for time period (kWh)}
Summer16.41495
Autumn17.41589
Winter19.51776
Spring19.31757
Year18.16617
3

An electricity company charges \$0.235 per \text{kWh}. How much more would a typical household expect their electricity bill to cost in Spring than in Autumn?

\text{Usage per day (kWh)}\text{Usage for time period (kWh)}
Summer16.41495
Autumn17.41589
Winter19.51776
Spring19.31757
Year18.16617
4

The cost of water has risen from \$1.20 to \$2.10 per litre.

a

Under the old price, how much would Eileen pay if she uses 489 \text{ L} of water?

b

If Eileen uses the same amount of water this year, how much will she have to pay under the new price?

c

If Eileen wants to pay the same total amount this year as she did last year, how much water should she use? Round your answer to one decimal place.

5

The table shows Uther's average water use for one day:

a

How much water is Uther using per day?

b

How much water does Uther use in a week?

c

If Uther only used the washing machine once a week, how much water would he use in a week?

d

What percentage of Uther’s daily water usage is taken up by gardening? Round your answer to the nearest percentage.

e

If water costs \$2.70 per kilolitre, how much would Uther have to pay per day?

UsageLitres per day
\text{Dishwasher}29
\text{Washing Machine}38
\text{Gardening}13
\text{Toilet}29
\text{Shower}53
6

A water saving shower head uses 60\% of the water an ordinary shower head does.

a

If Sharon uses 5.8 \text{ kL} of water to shower each month, how many litres would she save with a water saving shower head?

b

If water costs \$1.9 a kilolitre, how much money would Sharon save?

7

The pie graph shows the annual water usage in kilolitres for a household:

a

Calculate the amount of water that was used (in kilolitres).

b

State the percentage of the total water usage that was taken up by the car, correct to one decimal place.

c

If the car required 20\% less water every year, calculate the amount of water that would be saved per year (in kilolitres).

d

If water costs \$1.10 per kilolitre, how much does this household have to pay?

e

How much would the household pay if they used 20\% less water for the laundry but 10\% more for the shower?

8

Consider the following households and the approximate gas usage:

  • Households with 1 - 2 residents use on average 3100 \text{ MJ} of gas per quarter.

  • Households with 3 - 4 residents use on average 5400 \text{ MJ} of gas per quarter.

  • Households with 5 or more residents use on average 6400 \text{ MJ} of gas per quarter.

If gas is charged by the gas company at \$0.027\,51 \text{ per MJ} for the first 1220 \text{ MJ}, and \$0.022\,83 \text{ per MJ} for the remaining, calculate the quarterly bill of the average household with 3 to 4 residents.

9

Sophia is preparing a budget. Her gas usage over the past year for each month is given on the following table:

a

Predict Sophia's energy usage for the following month by using her average monthly energy usage. Round your answer to the nearest megajoule.

b

The fixed usage cost is \$0.028 \text{ per MJ} and the supply charge is \$18 each month. These rates are inclusive of GST. Find the cost of Sophia's expected gas bill for the next month.

c

Sophia has accounted for \$90 per month for her gas bill in her budget. Has she budgeted enough?

MonthUsage
\text{March 2019}2430 \text{ MJ}
\text{February 2019}2436 \text{ MJ}
\text{January 2019}2351 \text{ MJ}
\text{December 2018}2447 \text{ MJ}
\text{November 2018}2354 \text{ MJ}
\text{October 2018}2444 \text{ MJ}
\text{September 2018}2353 \text{ MJ}
\text{August 2018}2448 \text{ MJ}
\text{July 2018}2434 \text{ MJ}
\text{June 2018}2361 \text{ MJ}
\text{May 2018}2362 \text{ MJ}
\text{April 2018}2444 \text{ MJ}
Household bills
10

The following table shows details from an electricity bill of a small business:

a

Calculate the amount for the off peak electricity usage.

b

Calculate the supply charge for the 28 days of the billing period.

c

Calculate the total amount due.

d

If a 10\% GST is applied to the total amount due, calculate the final total for the bill.

11

The details of Holly's internet bill and billing history is given below:

Using the current bill and bill history, calculate Holly's predicted weekly expenditure on internet.

Use the fact that there are 52 weeks in a year.

MonthsBill charge
\text{August}\$29.30
\text{July}\$37.50
\text{June}\$30.00
\text{May}\$45.00
\text{April}\$23.20
\text{March}\$33.60
\text{February}\$47.10
\text{January}\$38.30
\text{December}\$25.10
\text{November}\$18.70
\text{October}\$30.00
12

The following information is taken from Joanne's latest gas bill:

a

State the type of plan Joanne is on with the energy company.

b

State the unique number identifying Joanne’s address as a gas connection point.

c

State the unique number identifying Joanne’s gas meter.

d

Given that the meter readings are in cubic metres, write down the amount of gas used for the supply period in cubic metres.

e

The amount of gas used in megajoules can be found by multiplying the gas used in cubic metres by the heating value and conversion factor. Find the amount of gas used in megajoules. Round your answer to two decimal places.

f

What word on the bill may indicate to Joanne that her gas meter readings may not be correct and why might this be the case?

g

During what time period is the energy company next planning to read Joanne's meter?

13

The following information is taken from Angela's gas bill:

a

State the billing period for this bill.

b

State the type of plan that Angela is on.

c

State the unique number identifying Angela's address as a gas connection point.

d

Determine the amount of gas, in cubic metres, consumed during the billing period.

e

Determine the amount of gas, in megajoules, consumed during the billing period. Round your answer to the nearest megajoule.

f

What word on the bill may indicate to Angela that her gas meter readings may not be correct and why might this be the case?

14

Consider the following quarterly water bill:

a

State the total amount due.

b

What was the amount due on the previous water bill?

c

How much water was consumed during this quarterly billing period?

d

State the water usage charge.

e

State the price of water per kilolitre.

f

How many litres of water were used on average per day? Round your answer to the nearest litre.

g

If the price of water rises by 10\% next quarter, calculate the new price per kilolitre.

15

Consider the following gas bill:

a

State the total amount due.

b

What is the length of the billing period in days?

c

How many megajoules of gas were used?

d

Calculate the average amount of gas John used per day. Round your answer to the nearest 20 \text{ MJ} per day.

e

Calculate the total usage and supply charges before any discounts or GST.

f

The bill indicates that a 12\% discount is awarded if the bill is paid on time. On which charge has this amount of \$9.22 been calculated?

16

A NSW electricity company has a product called Green Power which allows customers to have a certain percentage of their electricity generated from renewable sources.

Bill currently pays a flat rate of \$0.3445 \text{ per kWh} for his electricity. Bill would like to help support Australia’s renewable energy industry. He understands that if he switches to 100\% Green Power the cost of his electricity will increase by 5 \text{c per kWh}.

a

On his last electricity bill, Bill's average daily electricity consumption was 8.5 \text{ kWh}. Calculate the cost of Bill's average daily electricity consumption on his last bill.

b

Work out the cost of his average electricity consumption for a week.

c

Calculate the cost of Bill's average weekly electricity consumption if he switches to using 100\% Green Power.

d

How much extra would Joe be paying for electricity each week, if he uses 100\% Green Power?

e

Bill doesn't wish to pay more than \$5 per week on average if he switches to Green Power. Can Bill make the switch?

17

Consider Sally's water bill below:

a

State the total amount due.

b

State the length of the billing period.

c

State the total supply charge (fixed charges).

d

What percentage of the total amount due are supply charges? Round your answer to the nearest percent.

e

On average, how many litres of water has Sally used per day during the billing period? Round your answer to the nearest litre.

f

NSW Water has informed Sally that on her next billing period the cost of water is increasing by 12 cents per \text{kL}. If Sally’s total water usage over the next billing period remains the same, how much extra will she be paying on her bill?

18

The following table shows the monthly charges listed for Deborah’s natural gas account:

a

Deborah uses exactly 5000 \text{ MJ} in January. Find the total monthly cost.

b

In February, Deborah uses 13\,500 \text{ MJ} more than she did in January. By how much does her total monthly cost increase?

c

Find the total monthly cost that Deborah has to pay on her gas bill in February.

d

Calculate the average charge that Deborah paid per \text{MJ} of gas in February.

Amount usedCharges
\text{First }5000 \text{ MJ}\$0.0192 / \text{MJ}
\text{Next }13\,500\text{ MJ}\$0.0155 / \text{MJ}
\text{Supply Fee}\$80.00
19

Consider the council rates bill shown below:

a

State the time period covered by this bill in years.

b

State the value of Brian's property in dollars.

c

How much did Brian pay in rates for the value of his property?

d

Calculate the percentages of the total amount of the bill attributed to the following, rounding your answers to the nearest percent:

i

Residential value.

ii

Stormwater management.

iii

Domestic waste management.

20

The table shows a family’s energy consumption in percentages:

CookingWater heatingAppliancesHeating and cooling
6\%20\%30\%44\%

In the last quarter, the family’s electricity bill showed a balance of \$203.6772 and 1080 \text{ kWh} of electricity use. Currently all their energy usage is electricity based.

a

Find the cost of electricity per \text{kWh}. Do not round your answer.

b

Gas energy costs 3.549 cents per \text{MJ}. If they convert the water heating from electricity to gas energy, how much can they expect to save in the next quarter? Note that \\ 1 \text{ kWh} = 3.6 \text{ MJ}.

Energy plans and tariffs
21

Sophia is currently on a fixed rate electricity plan and is considering switching to a flexible plan where her electricity usage is charged different rates depending on the time of day. Sophia estimates she uses approximately 9.5 \text{ kWh} of electricity per day.

Flexible plan

Charge typeRate
\text{Peak usage}58.79 \text{ cents per kWh}
\text{Shoulder usage}26.72 \text{ cents per kWh}
\text{Off peak usage}16.26 \text{ cents per kWh}
\text{Supply}89.76 \text{ cents per day}

Fixed rate plan

Charge typeRate
\text{Usage}31.41 \text{ cents per kWh}
\text{Supply}89.76 \text{ cents per day}
a

If Sophia stays on the fixed rate plan, find her total electricity costs for a 92-day period.

b

Sophia estimates that during an average day she would use 2.5 hours of peak time, 5 hours of shoulder time and 2 hours of off peak time electricity. Calculate her total electricity costs for a 92-day period on the flexible plan in dollars.

c

Which plan will give Sophia the most savings?

22

The Wu family are conservative users of electricity and have solar panels installed on their roof. Their electricity usage is measured by a 'smart meter' which sends usage data direct to the energy company. It is why they have no meter readings on their bill. They are on a time of use plan called 'Flexible Saver' which have the rates given. They also get a solar feed-in credit on their bill for unused solar electricity that is fed back into the grid. Their rates are summarised in the tables below:

Charge typeRate
\text{Peak usage}53.01 \text{ cents per kWh}
\text{Off peak usage}14.42 \text{ cents per kWh}
\text{Shoulder usage}23.79 \text{ cents per kWh}
\text{Supply}96.85 \text{ cents per day}
Credit typeRate
\text{Solar feed in}9 \text{ cents per kWh}

Their usage summary and solar feed summary are given below:

Usage summary

Period: 28 Jun 18 to 26 Sep 18 (91 days)

\text{Meter no.}\text{Usage type}\text{Previous read}\text{Current read}\text{Usage (kWh)}
067458\text{Peak}--113.173
\text{Off peak}--148.631
\text{Shoulder}--281.399

Solar feed summary

Period: 28 Jun 18 to 26 Sep 18 (91 days)

\text{Meter no.}\text{Previous read}\text{Current read}\text{Export (kWh)}
067458--233.347
a

Calculate the total usage cost for the billing period.

b

The energy company provides an 18\% discount on usage costs if the bill is paid on time. Calculate the revised usage cost if the Wu family pay before the due date of the bill.

c

Calculate the total supply cost for the billing period.

d

Hence, find the total electricity cost.

e

Find the total electricity cost after a 10\% GST is applied.

f

Find the total credit they receive from the solar electricity they fed back into the grid.

g

State the cost of the entire bill.

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Outcomes

MS11-2

represents information in symbolic, graphical and tabular form

MS11-5

models relevant financial situations using appropriate tools

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