Reference and tools...


Heatmap display tool

Online calculators

Estimate combustion losses based on flue-gas measurements

U-value of simple layered structure. Define your structure by entering the material and thickness for each layer, inside to out. Includes condensation risk assessment.

Estimate steady-state heat loss from a building. Up to eight building element types (walls, windows, etc.) across five zone.

Free UK degree-day figures

Now available from the Energy Management Register web site. You need to join as a member (free of charge) to see them. Please visit

Download Energy management leaflet 7 (PDF format) for basic information about degree-day data and how to use them, or view frequently-asked questions.

Energy prices

Follow this link for UK Goverment quarterly energy price bulletins which includes comparisons of fuel prices in the EU and G7 countries

UK natural gas calorific values

Natural gas is metered by volume and its energy content varies with its pressure, temperature and calorific value. Higher supply pressure and lower temperature both increase the density of the gas, increasing the energy delivered per volume delivered (and vice versa). The illustration shows a corrector readout, piggy-backed on a gas gas meter.

The composition of the gas also changes slightly from time to time, which means that the calorific value (energy content per unit mass) will also vary. The CV is reported on invoices. There is no in-line equipment which can be used to measure the CV between bills; however, the UK is split into 33 local delivery zones (LDZ) and daily reports of CV for each LDZ are posted here by National Grid. This information enables you to convert pressure-and-temperature-corrected volumetric readings into energy terms more accurately in between invoices if, for example, you are trying to monitor on a weekly basis.

Going equipped

If you are doing your own energy surveys (or doing them for clients) have a look at the list of
recommended equipment

Reference data

Physical constants, calorific values, units of measurement and other authoritative reference data are available free in the on-line version of Kaye & Laby 16th edition. (V.V. 27 Oct 05)

Conversion factors

Energy content of fuels typical conversions from metered units (eg litres of oil) to kWh.
View short table. See also UK government spreadsheet with more extensive range of fuels, including estimated historical averages by industry for those fuels with variable properties.

Transport CO2 emission factors: UK government guidance

Neat units-conversion program: download free from (V.V. 14/10/05)