Welcome to saving energy
Introduction
1 Before the course starts
2 Measuring energy usage
2.1 Introduction to measuring energy usage
Description
2.2 Meters
Description
2.3 How to read your meter
Description
3 Record your readings
3.1 The workbook
3.2 Vampires database
3.3 Unmetered fuels
3.4 Energy bills
For registered students
4 Energy monitors
4.1 Introduction to energy monitors
5 Plug monitor
5.1 Introduction to the plug monitor
Description
5.2 Getting started
5.3 Using the monitor
5.4 Difficult appliances
6 Home monitor
6.1 Introduction to the home monitor
6.2 Getting started
6.3 Using the monitor
6.4 T152 monitor support
For registered students
What next?
References
Next steps
Acknowledgements Acknowledgements
Acknowledgements Text
Unit image
Acknowledgements Don't miss out
Introduction
Welcome to Energy measurements at home (T152), the OU's course for energy savers. You are reading T152's Welcome unit.
This open-access component is available both to registered students (on the course website) and to visitors. It is provided so that:
1. Visitors may gain an insight into the workings and material of the course.
2. Visitors may experience for themselves how a few simple measurements can identify energy savings in their homes.
3. Registered students can prepare on OpenLearn before the course website opens, in particular by starting their systematic monitoring of home energy usage.
If you are a visitor please ignore passages addressed to registered students.
What you can expect
T152 is about the principles, practice and understanding of energy usage in a domestic setting. We, the course team, created it because we believe that measuring your energy usage can give you more understanding and control of that usage, and hence of your living expenses, your impact on the planet and perhaps even the market value of your home.
You should expect to spend between eight and ten hours a week studying it. However, this will vary from person to person and with different parts of the unit, because there's quite a lot of practical activity and people do practical things at different speeds!
Why T152 works
Students who engage with the course often reduce their home's energy usage, and sometimes magnificently: a student in the pilot presentation reported a 60% year-on-year reduction in electricity bills. We believe that of the features of the unit that are involved in this process, the following are paramount:
• you gain knowledge about energy and how it behaves;
• you develop a deep understanding of your home's energy usage, derived from a programme of measurements;
• you conduct a systematic review of every relevant aspect of your home;
• a structured programme of study focuses your attention for the duration.
When we look in detail at the actions that gave students their savings, we often find that these are not the 'usual suspects', i.e. not actions you typically see in the media's 'Top 10 energy-saving tips'. This is a consequence of the knowledge, understanding and systematic review working together.
This unit is from our archive and it is an adapted extract from Energy measurements at home (T152) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this Environmental sciencecurriculum area.
Learning outcomes
By the end of this unit you should be able to:
- get an initial feeling for how energy measurements lead to energy savings;
- see how a simple measurement experiment is conducted;
- start to read your meters;
- embark on a search for the energy history of your home in past fuel bills;
- install and use the two types of energy monitor associated with the course;
- conduct measurement exercises in your home;
- possibly reduce your home's energy consumption.
1 Before the course starts
If you are a registered student of T152 then you are recommended to start collecting energy measurements before the course begins.
By the opening date of the spring–summer presentation, you may have turned off your space heating and will have to wait for next autumn before you can examine it in detail.
By the opening date of the autumn–winter presentation, your water heating may be concealed within your space heating, and you would have to spend periods with each of them turned off in order to isolate and measure the other.
An early start to data collection may avoid these annoyances.
If it was too late for you to follow this recommendation before the course began then you should start collecting measurements as soon as possible. This simply means that you need to act upon the sections on reading your meters, unmetered fuels and the home monitor as your top priority. Raise any difficulties that you may be having in the forum.
2 Measuring energy usage
2.1 Introduction to measuring energy usage
The following material is available to both registered students on the course website and visitors on OpenLearn.
Why measure?
You can't control what you can't measure. Control requires understanding, and measurements create understanding.
Your motives for taking control of your home's energy usage will be personal. Improvements in costs, property values, carbon emissions and resource depletion are typical, and T152 expands on each of these. But the most appealing reason I've come across is based on a past student's observation of her family. Children are scared by media clips about climate change: 'Is there a happy ending?'. It means a lot to them if their parents are clearly in control, as shown by actions and expert explanations of what the family is doing and what it still has to do. They know the difference between these and empty reassurance.
What to measure?
Many home energy measurements have one simple objective: to quantify the amount of energy used between points in time, and to translate this into an average over a set timescale. Here is an example in which the points in time are two widely separated meter readings and the average is per day.
Description
This shows a calculation of daily average usage from two meter readings. The first reading is 6734 units, taken on 31/10/2002; the second is 23 667 units, taken on 27/10/2008. This gives a total usage of 16 933 units over 2188 days. Dividing one figure by the other shows that the average number of units used per day was 7.739.
End of description
The other typical objective is to uncover patterns (such as a sudden change) in a series of measurements. This requires a sequence (rather than a pair as shown above), taken at more or less regular intervals.
You can obtain the measurements you need in several ways:
- read meters;
- measure unmetered fuel;
- analyse energy bills;
- monitor an individual appliance;
- monitor the whole home.
The example above was based on two energy bills. Meter readings, fuel measurements and monitor readings are used over much shorter time intervals.
You can read meters, measure fuels and analyse bills without using monitoring equipment. Therefore you can – and should – begin such measurements before receiving monitors in the course mailing.
2.2 Meters
Meters measure energy usage at the level of the whole house. They are standard in domestic electricity and mains gas supplies, being essential to the pricing mechanism. They are sometimes found in off-mains supplies of liquid petroleum gas, especially where one bulk storage unit supplies multiple homes.
An energy meter counts continuously from the moment it is activated. It has no concept of the discrete deliveries of liquid and solid fuels. Instead, fuel usage is measured between two arbitrary points in time – meter readings – and is the difference between the units counted at the second reading and those at the first. Figure 1 shows an image of an electricity meter reading.
Figure 1 Electricity meter reading
Description
This is a photograph of an electricity meter. At the top are six revolving digits, five black and one red, with the magnitude of each digit given underneath. The first five digits are currently 2, 4, 5, 6 and 0, with the sixth (red) digit sitting about halfway between 7 and 8. Their magnitudes are 10 000, 1000, 100, 10, 1 and 1/10 respectively, but the red digit also has a graduated scale to the right whose magnitude is 1/100. This means that the reading on this meter is 24 560, with the sixth digit giving precision to fractions of a unit. Below the digits are the letters kWh, showing that the meter is measuring usage in kilowatt-hours. At the bottom of the meter is a rotating disc that gives even greater precision than the six digits at the top.
End of description
The unit here is a measure of energy, the kilowatt-hour (kWh). Electricity meters are unique in measuring energy content directly. Gas or liquid meters measure a unit of volume, which must be translated into energy content.
T152 teaches what you need to know about measures of energy and their translation.
2.3 How to read your meter
T152's Monitor installation guide provides extensive guidance on locating and accessing energy meters.
The safety advice in the Monitor installation guide applies whether or not you have registered for the course, and whether you are installing a monitor or just want to read a meter. You must study the safety advice in full. Be careful, particularly if your meter is hard to reach without the risk of a trip, slip or fall. Care may include having someone with you.
If you have any kind of digital camera, you can with a little practice get an excellent image of virtually any meter. It stops motion (gas meters can whizz round), gives you all the time you need to interpret a reading, and increases your ability to take a reading at a regular time of day even if you are too busy to record it immediately.
Interpretation
The images in the Monitor installation guide reveal an immense variety of energy meters. They do, however, share certain features, so that general guidance for reading them is feasible. All the energy companies appear to provide such guidance on their websites, so look at your suppliers' sites. In case yours are unhelpful, here are links to two 'How to read your meter' pages.
British Gas
Southern Electric
Precision
Disregard just one part of the energy companies' guidance when you measure your own energy usage: the bit about ignoring the least significant digits, i.e. the precision of the reading. Energy suppliers bill you only for whole units used, so they don't need or want the part units. You do.
Look carefully at the earlier image of an electricity meter. The supplier would bill only for the whole units, in this case 24 560 kWh. The red digit to the right of that is precise to 0.1 kWh, i.e. 24 560.7 kWh. The graduated scale to the right of the red digit is precise to 0.01 kWh, i.e. 24 560.74 kWh. Two decimal places are normally sufficient for home electricity meter measurements. The moving disc gives even more precision, revealing the reading to be 24 560.7379 kWh – this level of precision is more of a nuisance than a help.
The next image (Figure 2) is of a gas meter. You can see that its unit is a cubic metre (m³) of gas. Some older gas meters measure cubic feet (ft³)) and you are billed in a unit of 100 ft³).
Figure 2 Gas meter reading
Description
This is a photograph of a gas meter. At the top is information about the meter's manufacturer and some technical details that aren't relevant to T152. Below these are eight revolving digits, with the notation m3 to the right showing that the meter is measuring usage in cubic metres. The last three digits are surrounded by a red box and separated from the first five digits by a comma; the final digit has a graduated scale on the right to provide even greater precision. The digits are currently 1, 0, 5, 4, 5, 5, 9 and 0.
End of description
In this case, the decimal places in the red box give enough precision for most purposes, i.e. 10 545.590. Three decimal places are normally sufficient for home gas meter measurements. However, it is sometimes possible to use a gas meter to investigate a single device, such as a cooker, and while doing that you might also be interested in greater precision, such as the graduated scale on the last digit in this image. Reading between the graduations, it gives 0.0001 m³) precision, and this reading is 10 545.5901 units.
Activity 1 Reading your meters
With due regard to your safety, as advised above, try to read each of the energy meters in your home. Write down the readings to (a) the maximum possible precision and (b) the precision recommended above. Also note the date and time of the reading as precisely as you can.
Remember the trick of taking meter readings with a digital camera.
Heed and act upon whatever lessons this activity teaches, such as:
- ease of access to the meters and their visibility;
- difficulties in interpreting the readings;
- difficulties in being precise enough;
- using a clock or watch at the same time as reading the meter.
Practise again in an hour's time, and again tomorrow. You want meter reading to become second nature to you. You will also start to gain an idea of how much energy or fuel is used by your home over these timescales.
When to read your meter
You need to read your meters (and measure other fuels) regularly before and during your study of the course. It is useful to have at least a fortnight of daily readings for later analysis of patterns. As enthusiasm wanes, you might miss out some days. When more specific measurements are needed, the course text says so.
At one point in T152 you will study how to analyse and exploit variations in measurements. A particularly useful example is the variation in heating demand in response to changes in outdoor temperatures. With this in mind, you should try to take at least seven consecutive daily readings of whatever fuel you use for space heating. Any seven days will do – whichever are most convenient for you – although a weather forecast that suggests a significant change in average temperature during the week ahead might be a good prompt.
This point is especially important if you have registered for the spring–summer presentation. Take the measurements described above before your heating season finishes. If it has already finished, you may be able to discuss other students' results in the course forum, then get your own when heating restarts next autumn.
Try to plan all meter readings so that you stick as closely as possible to the same time each day. If you can't keep to the same time it isn't a disaster, but it does mean that your calculations will have more uncertainties built into them. Include both the date and the time alongside the quantity when you record any reading. The next page describes how records are kept in T152.
3 Record your readings
T152 provides a workbook in which you record your data and which provides calculations and guidance for you. Essential reading to check that you can use the workbook is on the T152 web page entitled Before you register, to which the registration process directs you. If you have not looked at it, go there now.
3.1 The workbook
You can download the course workbook by clicking here: Workbook.
If you are reading this on OpenLearn, the link above will provide you with a much reduced version of the course workbook to enable you to record data. If you are a registered student waiting for the course to open, I strongly urge you to use this version in the meantime. It is designed so that data can be copied across when the full workbook becomes available.
When you need to use the workbook, the course text will direct you to the required worksheets.
The following activity gives you an opportunity to use the workbook and to save energy.
Activity 2 A Vampire experiment WORKSHEET: METERS, WEEK 1
'A Vampire experiment'?! The name comes from David MacKay's book Sustainable Energy – without the hot air. Vampires are gadgets that consume power while you aren't looking, sucking the energy lifeblood from your home.
First read chapter 22 from MacKay's book, which is about efficient energy use. Your goal is to reproduce his experiment in your home, substituting your meter readings. Here is a suggested approach:
- Read your electricity meter immediately before and after periods in which the home is properly at rest. 'At rest' means that nobody is in or everybody is asleep, and no appliances are on except the 24-hour background that you leave on, e.g. fridge-freezer, security alarm, fish tank, etc. Put a reminder to read the meter in a place where you are unlikely to miss it when you get up or return home.
- Some periods must reflect your normal household habits. Before other periods, you should systematically switch off and unplug every unnecessary gadget for the duration. 'Unnecessary' gadgets are any that are left on standby or inactive, such as kitchen and audiovisual equipment, chargers that have done their job, and most computers and stuff connected to them. 'Necessary' gadgets are those whose very purpose involves being left on and active, without which someone or something might be harmed or damaged, such as the fridge-freezer, security alarm and fish tank. Leave these on.
- It might be best to begin with all the normal periods, because embarrassment and the desire to save money can make you unwilling to switch some vampires back on to complete the activity!
- As you can see from the variability in MacKay's Figure 22.2, just one period of each type can give a reasonable impression, but several combined give a more representative view. This is very typical of home energy measurements.
- Enter each meter reading (both the start and the end of the period) with its exact date and time into the 'Meters' worksheet. Very precise readings are worthwhile in this instance, as periods may be short and energy levels low.
- To discover what the results tell you, copy the relevant readings to the 'Vampire experiment' calculator in the 'Week 1' worksheet.
The Vampire experiment does two things for you: