magnetic ballast
mantle protector
manure
masonry heater or stove
masonry oven
mass burn facility
MATERIALS AND MATERIALS SCIENCE
maximum power point (MPP)
maximum power point tracker (MPPT)
measuring tape
mercury vapor lamp
metal halide lamp
methane
methanol (CH3OH)
micro wind turbine
microhydropower
microturbine
mineral wool insulation
miter saw
mixing ratio
moisture control
moisture control in basements
moisture control in walls
molten carbonate fuel cell
monoculture
mortar
mortiser
motion sensor lighting control
motor
multifuel firelighting pellets
multifuel pellet stove
multifunction inverter
multijunction device
municipal waste