Magnets
Sometimes misleadingly claimed to improve combustion efficiency: read full article.
MCS
(UK) Microgeneration Certification Scheme
Meter reading, automatic
Click here for an article.
Meter reading, manual
Click here for an article on the subject.
Meters, flow
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Meters, small appliance, plug-in
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Meters, justifying extra
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MEUC
(UK) Major Energy Users' Council
MID
Measuring Instruments Directive 2006. Applies to meters used for resale of energy and water. An excellent explanation can be downloaded from SHM Communications, one of the largest European stock holders and distributors of metering products.
Monitoring and targeting
Systematic process of periodic (typically weekly) assessment of actual consumption against the minimum expected quantity given the prevailing conditions; and various related analyses. More..
Motors and drives
Electric motors account for substantial proportion of consumption in manay organisations and this article gives some outline guidance on reduction opportunities.
M&V
Measurement and Verification: the process of objectively and fairly quantifying the effect of an energy conservation measure.

Motor fitted with auxiliary cooling fan, enabling it to be run at variable speed