(1) While start-up and electricity costs mean the farming method is still more expensive than relying on the sun ... (2) 'In terms of land use, this is 4,000 times more efficient than regular farming ... (3) The invention is billed as a way to develop purely organic vegetables with less labour ... (4) Red LEDs require less power, cutting the electricity bill by 60 per cent ...
When making comparisons, we generally compare (a) the degree of a condition, in which case we modify the adjective, using '-er' (cleverer), 'more' (see 1 and 2) or 'less' (less expensive, less clever); or (b) the amount of something, in which case we modify the noun, using 'more' (for both countable and uncountable nouns - more men, more water), 'less' (for uncountable nouns - see 3 and 4) or 'fewer' (for countable nouns - fewer men. In conversations, people sometimes say 'less men'; try to stick to 'fewer' in writing). Note that we don't use 'fewer' to compare adjectives but nouns, i.e. we never say 'fewer expensive' but 'less expensive'.