10 Downing Street

Since 1 October 2008 public buildings in the UK over 1,000m² have been required to display a Display Energy Certificate (DEC) prominently at all times. Display Energy Certificates were introduced by the Government in response to the EU Energy Performance of Buildings Directive which all EU member states were required to implement by January 2009.

DECs are designed to promote the improvement of the energy performance of buildings. They are based upon the actual energy performance of a building and increase transparency about the energy efficiency of public buildings. DECs use a scale from A to G with A being the most efficient and G the least. The Display Energy Certificate for 10 Downing Street is available through the link on the right.

no.10's historical resource use is available in these CSV files. We are deciding which other formats to provide data in, so if you would like to use the data for a purpose that requires another kind of file or feed, then let us know, and we'll see what we can do!

How do you calculate the CO₂ emissions from a unit of electricity, gas or district heating used?

Energy retailers and the government produces conversion factors that describe the typical carbon impact of different energy sources. These allow us to take the electricity use (in kWh) and gas use (in m³) and district heating use (in kWh) , and calculate the approximate carbon dioxide emissions, normally measured in kilograms of carbon dioxide equivalents (kgCO₂e). Defra's UK conversion factors may be found at Defra's 2011 Guidelines. The factors in use at each particular building are noted below in the Notes section.

Why is there no scale on the small real time graph?

We made a small, simple real time display graph (we call it a 'teaser') so that organisations can communicate about real-time energy use on their homepages. The intention of the teaser is to present very simple, somewhat intriguing information that attracts browsing users to the profile page (this page!). It has to work in a very small area, and it can't support detailed enquiry.

The building profile page where you are now is where the real information lives. This is where we provide much more detail for those who have the time and inclination to learn more.

How do you get this data from the buildings?

Getting this energy data out of some buildings is harder than others, but in general the buildings contain a small low-power computer which takes very frequent readings from the electricity, gas and district heating meters and stores the data. Every few seconds, this computer sends the information it has collected to a server. Your browser will then ask this server for the data it needs in order to draw the real-time detailed graphs and website teasers. The energy impact of this process is very low, and it gets lower with each additional site that uses the system.

What do the colours on the graph mean?

The colours in the graph show approximately how the current level of usage would lead to a given Operational Rating – as set out on a Display Energy Certificate (DEC) – if the performance for a given moment carried on for an entire year. This goes from dark green for ‘A’ to red for ‘G’. We calibrate this using input data used for generating the building’s DEC, together with information relating to 'normal' buildings of its type.

Why are you using these units and what do they mean?

We provide three different measures of the energy used: the amount of energy, its monetary cost, and the carbon impact of the energy used.

Energy use is measured in kilowatt hours (kWh), which are the standard units of a home energy bill (1kWh is the amount of electricity used by ten 100W light bulbs in one hour).
For electricity this number represents the amount of energy that flows into a building through the meter, and excludes distribution losses. For gas it is the amount of energy that is theoretically available by burning all the gas in an imaginary burner. For district heating it reflects a flow of temperature into the building over time (after the heat produced by burning the fuel has been transported to the meter, which involves other losses). So these numbers, while all being measured in kWh, mean very different things. This is one reason that we prefer to use 'units per hour' when combining them. In some ways it would be better not to combine them at all, because it implies that the measures are comparable. This is a global challenge though, and conventions have become established around combining kWh. So we'll have to fix it another day.

Monetary cost is calculated using the costs per 'unit' for each utility in every building. The figures used are noted below in the Notes section.

The carbon impact is measured in kg of CO₂e (the e stands for equivalent) which takes other climate-affecting gasses into account besides carbon dioxide.

How much does this organisation pay for its energy?

Prices come from the latest energy bills for Number 10, which are noted below in the Notes section. These are of course subject to change, and will be updated by the organisations themselves as tariffs are revised.

Can you show data from the transport emissions of this organisation/ building?

Data of CO₂ emissions created by transport used by organisations is very interesting and powerful data to show here. We are working on ways to display and reduce the transport impacts of different organisations, and you will see some of the products of this work on these pages very soon.

one

Carbon conversion factors of grid electricity, gas and district heating are based on Defra’s 2011 guidance. The factors in use are 0.18360 per kWh for gas and 0.2433 per kWh for district heating and 0.52462 per kWh for electricity.

two

Prices come from the latest Number 10 energy bills, which for Gas average out at 3.04p per unit and for district heating average out at 2.90p per unit (please note that we currently are using the net price as no bills for this year are available yet) and for electricity average out at 8.67p per unit. The gas volumetric measurement is converted to kWh using the meter correction factors and calorific values supplied by the utility company. These may be subject to change.

three

As far as the widget is concerned, there are 12 distinct 5-second periods in a minute. The real-time data is for the five second period just ended, which means that sometimes the widget could display values that are nearly 10 seconds old.

four

Because we have used the pulse-outputs of electrical and gas meters there are certain assumptions we need to make in order to generate a real-time value. The pulses from the meters actually signify a volume of gas or an amount of energy, and we need to determine a flow of gas or electrical power from the pulses. Since at any given moment you are always between one pulse and the next, you have to

guess, to a certain extent, when the next pulse will come in order to estimate the actual flow or power. The accuracy of the guess depends on how close together the pulses are, so at busy times you hardly need to guess at all. The pulses from the main electricity meter come every 100 watt-hours, which is enough to let us overcome the issue by counting the number of pulses in a five second period and applying a calculation to smooth successive readings into a rate, even at night. The main gas meter pulses once for each cubic metre consumed, which for properly variable loads could leave us guessing for quite a while before the next pulse comes.