100 Parliament Street, London

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About this building

100 Parliament Street is occupied by HM Revenue & Customs and Department of Culture, Media and Sport. (The division of energy consumption is approximately 86:14 between the two departments, see details below.) Meanwhile, HM Treasury occupies the 1 Horse Guards Road side of the building. The building was originally designed in 1898 by John McKean Brydon and completed by Sir Henry Tanner. Winston Churchill had a suite of offices on site during World War II and made his VE Day speech from the balcony of what’s now called the Churchill Room. The site was listed as Grade II in 1970. 100 Parliament Street currently provides work space for around 2000 members of staff and hosts around 4000 visitors a month.

Our energy use

100 Parliament Street, London

This graph allows everyone to access a range of data from our offices at 100 Parliament Street. It’s generated in real-time from data taken every 5 seconds from the on-site meters.

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Building Stats

Year Built
Number of floors
Total usable floor area
48965.0 m2
Heating Type
District heating
No. of Occupants

Display Energy Certificate

Since 9 January 2013 public buildings in the UK over 500m2 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 100 Parliament Street, London is available here or by clicking the plaque on the right.

Study our data

100 Parliament Street'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 , and we'll see what we can do!

Frequently asked questions

How do you calculate the CO2e emissions from a unit of energy used?

Energy retailers and the government produce conversion factors that describe the typical carbon impact of different energy sources. These allow us to take the energy uses (in their respective units), 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.

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 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. If we do not have data for all of the utilities noted in the DEC then the graph will appear in greyscale, to indicate that the usage displayed on the graph is not representative of the full energy use of this building.

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.

Why isn't the graph updating?

Occasionally the data connection goes down and the graph isn't automatically updated with the current information. This is nothing to worry about. During these periods, all of the data is saved and we will fill in the graphs with the backdated information as soon as possible.

How much does this organisation pay for its energy?

Prices come from the latest energy bills for HM Revenue & Customs, 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 CO2e 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.

What is HMRC doing to reduce energy consumption in 100 Parliament Street?

Our 100 Parliament Street building receives heat via the Whitehall district heating system, which serves other Government HQ Sites locally. The site has a mixture of naturally ventilated and mechanically cooled offices and rooms.

Display Energy Certificates (DECs) indicate the energy performance of a building. Each allocates a numerical indicator which relates to the annual CO2e emissions from the building - the lower the numerical indicator, the better the energy efficiency of that building. An energy performance operational rating of 100 would be typical for an historic building of 100 Parliament Street’s type so the current rating of 83 is good.

The rating was improved from 84 in 2008 by reducing the building’s core temperature from 23° C to 21° C.

What other measures is HMRC taking to reduce carbon emissions?

In addition to reducing carbon emissions from our offices, HMRC has also focused on reducing emissions from business travel. We have already exceeded our government target to reduce carbon emissions from road vehicles by 15% by 2010/11 (against a baseline of 2005/6) and current data for 2009/10 shows we have reduced emissions from road vehicles by a total of 36.43%. (These figures include both HMRC and its executive agency, the Valuation Office Agency).

What is HMRC doing to reduce energy consumption by 10% across the HMRC estate?

HMRC has a complex and disparate estate, from listed historical buildings to ‘60s office blocks and new builds. Surveys are taking place on a building by building basis to identify no-cost and low-cost ways to reduce our carbon emissions. These include voltage optimisation; temperature adjustments similar to 100 Parliament Street and replacing halogen lights with low energy LED alternatives.

How much energy does each department consume?

100 Parliament Street is occupied by both HM Revenue & Customs and Department of Culture, Media and Sport. Of the total consumption displayed in the energy graph, it is estimated that 86.45% is consumed by HMRC and 13.55% by DCMS.



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


Prices come from the latest energy bills, which 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.


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.


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. We use an ‘exponential moving average’ calculation to generate the real-time value, which allows us to display a value that is as close-to-right as possible; the values go up in time with increases in actual use, but lag behind sudden reductions. The downside of this is that if you added up all the real-time values that the teaser shows every five seconds, over time it would be shown to over-report slightly. This inaccuracy in the real-time data is strongest when high gas use drops quickly (as when the main boilers shut down, which happens several times a day). This distortion in the real-time data does not introduce any inaccuracies into the archive data, and we will report on the exact degree of error introduced if there is interest in this.