# 'Less' or 'lower'

I am struggeling with deciding between 'less' or 'lower'. For example I have the three sentences:

1. Method A leads, on average, to 50 kWh less/lower surplus energy per day.
2. The results show that the developed methods, on average, lead to 10% less/lower costs.
3. In periods with less/low PV generation, the electrical load is strongly reduced.

Is there any general rule regarding this or can you give me a general advice? I'd appreciate every comment.

A simple but unhelpful answer is that it's idiomatic for each noun and you just have to learn them by exposure to lots of numbers, then you get a feeling for which one is right.

For a more complex and hopefully helpful answer, let's start with a concrete example. If you have a glass with some water in it, the water is a measurable quantity (less/more), and the height of the top surface is a level (high/low). You would ask, "How much water is there?", and, "How high is the water?"

For each abstract idea like "energy", "cost", and "generation", we have a mental concept of whether it's a quantity or a level. If we think of it as a quantity, we use "less/more". If we think of it as a level, we use "higher/lower".

Generally, we see "energy" as something measurable, we see "cost" as a level, and we see "generation" (and noun forms of verbs generally) as measurable. So,

1. less surplus energy
2. lower costs
3. less PV generation

Now, you may see things like "low energy", "less costs" and "low PV generation". Understand that these are informal ways of saying, "low energy level", "fewer costs (in the countable sense of 'cost')", and "low PV generation levels".

• Thanks gotube for your answer. For me costs are definetely measurable. Commented Apr 18, 2020 at 19:48
• What about the word 'share'? Would you use 'less than 10%' or 'lower than 10 %'. And again for me 'costs' are definitely measurable. Because of this I don't know how apply the rule posted by gotube Commented Apr 19, 2020 at 7:02
• Would you say, a) "How much cost is there?" or b) "How high are the costs"? If you say b), then you understand the concept of levels. If not, then yeah, you're back to the first paragraph of my answer :/ Commented Apr 20, 2020 at 8:14
• "Less than 10% share" feels better to me. "Lower than 10% share" is... okay... but it sounds like the level is important, like there's a trigger at 10%, so the level relative to 10% is important, whereas "less than 10% share" sounds neutral Commented Apr 20, 2020 at 8:17
• Thanks gotube for your answers and help (I accepted it). Commented Apr 20, 2020 at 8:28