FAQ
About iMeasure
What are the benefits of using iMeasure?
How often do I need to enter my energy meter readings?
What carbon emissions factors are being used in iMeasure?
Does imeasure give me credit if I purchase a green (renewable energy) electricity tariff?
Why has Oxford University's Environmental Change Institute created iMeasure?
I want to know more about Internet-based energy and carbon measurement tools
Account administration
I am having trouble logging into my account
Which web browser versions are required to run imeasure?
How do I read my electricity meter?
How do I change the unit of my meter(s)?
Do I have to take meter readings on a Monday?
Error - week ending must be unique
When do I start getting results about my energy use, carbon emitted & money spent?
Can I back-date my building profile if I have old meter readings?
How has the amount of money I spend on energy been calculated?
Why is the floor area essential for the feedback on energy use?
Results and Analysis
What is the building base temperature?
How do I interpret my building's energy performance line?
What is the control chart telling me?
What are normalised and non-normalised consumption?
What is imeasure?
imeasure is an online tool to help you accurately monitor your home energy use and carbon emissions. It calculates your energy use based on the energy meter readings that you enter. Each time you enter your readings into imeasure your results will automatically update and give you immediate analysis on your household's energy use, spend and carbon dioxide (CO2) emissions.
imeasure uses innovative Degree Days analysis which reconciles weekly energy use with outside temperature. Our analysis will tell you how energy efficient your building is and where you can make improves to save money.
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What is the benefit of me using imeasure?
imeasure is a quick way to keep on top of how much energy you are using before your energy bill comes. With energy prices going up imeasure will help you spot opportunities for saving energy and therefore money! Also, most times your energy bill will only be an estimate of your energy use, therefore, you can use your imeasure meter readings to tell your energy suppliers your actual energy use so you will be billed correctly.
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How do I get started?
Simply click “Sign up now” and follow the instructions. You can monitor electricity, gas, heating and LPG meters. It is important to check the units on your meter when you set each one up.
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How often do I need to enter my energy readings?
We recommend taking readings on a weekly basis because as this will help make home energy management part of a routine. However, imeasure works just fine if you want to update your profile less frequently. In addition degree days data is provided on a weekly basis so entering your readings regularly will improve the accuracy of this analysis.
We will send you a weekly email on a Monday to remind you to record your meter readings (you may opt-out of this at any time). We also use the email to share relevant news about energy management, climate change research, policy and energy saving tips. And sometimes some news just for fun.
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What carbon emissions factors are being used in imeasure?
imeasure uses emission factor guidance from DEFRA. The most recent figures released by the department are used and currently these are the 2009 factors.
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Does imeasure give me credit if I purchase a green (renewable energy) electricity tariff?
imeasure does not reduce your carbon emission totals if you purchase a green tariff because the DEFRA carbon emissions factor for electricity takes into the amount of renewable energy inputted into the national grid. imeasure is about the opportunities to reduce demand for energy in the home rather than relying on supply-side carbon emission reductions.
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What is a community?
Formerly “Carbon Clubs”
imeasure communities let you group together with other users and work together to reduce energy use. For example a community may be set up for households in the same geographical area or in similar urban environments. Often communities run alongside wider low carbon initiatives. The community results page gives figures on the average energy use for homes in the community so that you can see you compare.
If you would like to set up an imeasure community please email alex@imeasure.org.uk
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<--I am having trouble logging into my account
Q: I forgot my password. Can you send me a new one? A: Click 'reset your password' on the sign-in page.
Q: I reset my password last week but I still can’t login this week
A: Make sure you are using your username to login and not your email address -->
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Which web browser versions are required to run imeasure?
imeasure will work with the latest Chrome and Firefox versions as well as Internet Explorer 8 & 9. This software does not support older versions of IE (7 and earlier) due to technical problems with these browser versions.
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How do I change the unit of my meter(s)?
You can change the unit of your meter by going to the meter tab and clicking edit for the meter you want to edit. Then there will be a drop down menu of the different unit options, select the one you want and click update.
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Do I have to take meter readings on a Monday?
No. You can take meter readings on any day of the week. However, imeasure will interpolate your readings to the Monday as this is the day heating degree days for the last week are imported into imeasure. Therefore, for the greater level of accuracy for assessing your building’s energy performance we recommend having the habit of taking your readings on a Monday. If you take your readings not on a Monday they will appear in italics to indicate it is an interpolated reading – the actual reading recorded is saved too.
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Error - week ending must be unique
The imeasure week runs from a Sunday midnight to the following Sunday midnight. Only 1 reading may be entered per week but it does not matter which day of the week the reading is entered.
imeasure expects readings to be entered on a Monday and if entered on a different day the system will interpolate what the reading would have been if taken on a Monday. These readings appear in blue. This is required becaues degree days data is produced for the week ending on a Sunday midnight. Not entering readings on a Monday is not any less accurate.
A reading entered on a Monday allows calculation of the consumption for the previous week ending on the Sunday midnight, this is why the week ending date is one day before the reading date.
If you take a reading and get the "week ending must be unique" error then you must wait until after the next Sunday midnight to enter your next reading.
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When do I start getting results about my energy use, carbon emitted & money spent?
You will start to get information about you weekly energy use spend and emissions after entering two sets of meter readings. After you have entered your thrid set of readings there will be enough data to produce degree days analysis for your home. The longer you use the system and the more readings you enter the better the analysis will be.
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Can I back-date my building profile if I have old meter readings?
You can back date a profile to August 2007, which is when we have the weather data from. However, unless you have a complete set of past weekly or monthly records for all your energy meters we recommend not backdating your imeasure and starting fresh. Most energy bills are estimated readings so these are not helpful as imeasure is based on actual energy use to give accurate feedback. imeasure will however do a linear interpolation between meter readings you enter to generate any missing weekly readings and consumption values, so this will give you a reasonable picture of your energy usage over time even if you have an incomplete set of readings.
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How has the amount of money I spend on energy been calculated?
imeasure gives you an indication of how much money you are spending on gas and electricity each week as well as your running total spend since starting to use imeasure. You can enter your own tariffs or imeasure applies a default tariff. imeasure uses the defaults of 3p/kWh for gas and 10p/kWh for electricity. imeasure simply multiples your energy use for each gas and electricity by the pence per kWh. These standard tariff rates do not include standing charges or VAT nor do they take into account of dual fuel rates (i.e. rates offered by utility companies providing you with both your electricity and gas) or a 2-rate system (i.e. one rate for the first x kWh you use and a second rate once exceeding x kWh).
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What is a sub-meter?
An electricity sub-meter is a meter that allows for the monitoring of usage on a portion of a distribution network past a main meter. I.e. the main meter records the total consumption and the sub-meter records the part consumption for the sub-metered area only. Thus the sub-meter's consumption is recorded in the main meter.
You should only use a sub-meter when you have setup a main meter that records the whole consumption (all sub-meters) and you wish to track the sub-meter consumption directly.
Note: All sub-meter consumption is not included in the building analysis, only main meters are included.
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What is a meter roll over?
Analogue meters have a set number of digits to record your consumption. When a meter reaches the maximum value it will reset to the first value and continue reading from this minimum value. Accordingly any direct comparison between the last maximum value and the new minimum value will result in a negative consumption value. imeasure understands when a roll over event occurs and recalculates the consumption based on input values and will return the positive value between these readings.
E.G. gas meter 1 has 5 digits starting at 00000 and reaching a maximum value of 99999. Any consumption after 99999 will result in the meter reading starting from 00000 again. So 100 consumption units past 99999 will read 00099 (99999 + 1 = 00000 + 99 = 00099), for a consumption unit value of 100 between these two readings.
The imeasure system checks for meter roll over events when you are entering readings. If you enter a reading value smaller than your last reading imeasure will notify you that it has detected a roll over event and ask you to confirm this is true. If you have know the roll over has occurred press ok, otherwise you may have entered your readings incorrectly. If you are unsure, you should take this opportunity to check your reading values are correct. If you do not check them the consumption value between these readings may not be correct. If you are unsure visit our help for reading electricity meters and gas meters.
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Why is the floor area essential for the feedback on energy use?
The floor area is not essential for plotting consumption, money spend and emissions against time or the performance line and control chart.
However the floor area is needed if you want imeasure to predict energy use/money spend or get an A-G energy efficiency rating.Back to top
What are degree days?
Heating degree days (HDD) are quantitative indices designed to reflect the demand for energy needed to heat a building. These indices are derived from daily temperature observations. The heating requirements for a given building are considered to be directly proportional to the number of HDD at that location. A similar index, cooling degree day' (CDD), reflects the amount of energy used to cool a building (these are not currently used in imeasure.)
Degree day data is required to isolate and discount the effects of outside temperature on your households energy use. Allowing you to focus on what is important. imeasure imports the weekly HDD for 77 weather stations around the country. In the building tab you will find a table listing the number of heating "degree days" for each week of energy monitoring. The greater the number the greater the integral between the building base temperature and the outside temperature.
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What is the building base temperature?
The building base heating temperature is the temperature below which your heating goes on. The default heating base temperature in imeasure is 15.5oC - this is the base temperature appropriate for most building types in the UK. Therefore, do not change the default setting unless you have additional information on what your base temperature should be set at in imeasure.
The imeasure energy-weather analysis compares the outside temperature to the energy needed to keep the building above base temperature and calculates your building’s efficiency.
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How do I interpret my building's energy performance line?
The energy performance graph plots energy use for heating against degree days. Degree days are a measure of outside temperature and a high value indicates a cold week. In a typical building you would expect the energy use to be higher during a cold week.
The slope of the best fit line tells you how much additional energy your building would use for an increase of 1 degree day. A high value (steep slope) indicates poor energy efficiency and a low value (shallow slope) indicates good efficiency. A negative slope is unphysical and probably indicates there is a error in your data.
R is the measure of the correlation between degree days and energy used. An R value of zero shows that external weather conditions do not affect the energy used in the building whilst an R of 1 shows that the energy used in the building perfectly follows the weather (and that all the data points lie on the best fit line). A high value of R is evidence of a good control system in a building and a low value can imply control problems. Recent work has shown that for an R value above 0.7, two months of data is sufficient to gain a yearly benchmark within 10% of actual annual energy use.
R < 0.87 below average R > 0.87 above average R > 0.93 well above average R > 0.97 excellent
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What is baseload?
Baseload is the amount of energy you building uses for heating irrespective of outside temperature. In most cases where the same fuel is used for space heating and heating water this corresponds to the energy use for hot water. This should stay approximately constant all year round.
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What is the control chart telling me?
The purpose of the control chart is to give you some feel for the fluctuations in your building energy performance. The chart helps you quickly detect if something might be amiss with your heating system or controls.
The control chart visually displays how your actual weekly energy consumption varies from your predicted energy consumption. Predicted energy use is calculated by imeasure using the equation from your performance chart line. The point on your control chart is then calculated by subtracting your predicted consumption from the actual consumption. The weekly point is given as a percentage above or below zero. The zero point is where actual energy use = predicted energy use. So when the percentage is positive, you have used more energy than predicted and when it is negative you have used less than predicted. If you have made a change to your building or heating controls and have saved energy this should show up as negative readings.
A control chart's line will naturally have a zig-zag appearance, i.e. fluctuate, because energy use in buildings changes and is difficult to predict exactly (for example because the weather changes, or someone leaves a light on or window open overnight by accident). However, you want to know when this fluctuation is more than expected as this suggests there may be a bigger or longer term problem (for example, the window is stuck open or the boiler is set incorrectly and over-heating). There are statistical methods for determining 'expected' levels of variation, however, at the moment in imeasure we have set the variation threshold as plus or minus 20% in the control chart. In the future we will be developing the functionality to let you set your own operating range and advise you what that range should be.
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What are normalised and non-normalised consumption?
On the results page for each of your buildings, under the “Report” tab is a table showing your annualised energy consumption, CO2 emission and cost. A normalised and non-normalised value is shown for each of these (with the non-normalised value displayed in brackets).
Normalised consumption has been standardised against weather data so that clear comparison can be made of total energy use between different years.
Non-normalised consumption is the actual consumption for a calendar or financial year where there is a full set of data for that year.
If there is missing data for this year then a warning will show. In this case the non-normalised result is interpolated from the year’s partial data.
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Why has Oxford University's Environmental Change Institute created imeasure?
The research of the Energy Group at the Environmental Change Institute is focused on developing a better understanding how the UK can significantly and rapidly reduce energy use and carbon emissions through behaviour change, technologies and policy interventions. There is very limited good household data to do this work well so we designed imeasure to help the energy research community. imeasure users will contributing to cutting edge research in energy issues. We will share our work with you as it progresses so you see the value of imeasure data. The more imeasure users there are the better our data can be so please do get involved and encourage your friends and colleagues to do the same.
All energy data from imeasure is anonymised and aggregated
for research purposes only. Please read the terms and conditions for
more details on how your imeasure data will be protected, stored and
used. Do contact us if you have any questions about imeasure.
alex@imeasure.org.uk.
imeasure
has been funded by the UK Energy Research Centre, which is an
interdisciplinary academic centre funded by the research councils to
examine how the UK transforms to an low carbon and secure energy system www.ukerc.ac.uk
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I want to know more about Internet-based energy and carbon measurement tools?
In preparation for creating imeasure the Environmental Change Institute did a detailed assessment of online carbon calculators. The findings of this assessment can be found by reading: “Internet-based carbon tools for behaviour change“
(http://www.eci.ox.ac.uk/research/energy/downloads/botrill07-calculators.pdf)
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What is next for imeasure?
The imeasure system is constantly under development. We would greatly appreciate hearing your ideas for
improving imeasure. Please email your feedback and comments to alex@imeasure.org.uk
We have a number of plans to expand the features of imeasure and these will be added in due course and we will keep you posted.
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