E stands for ....?

Since it snowed here on Friday night, the temperature has barely been above freezing and we've needed the central heating on quite a bit except for when we get the wood burner going in the evenings. Last night was the coldest of the winter so far and its been feeling decidedly frosty in the house all morning. The central heating didn't seem to be coping, we were still feeling chilly after it had been on for a couple of hours. 

DH set off in investigation mode and started going from room to room bleeding all the radiators as they didn't seem to be getting very hot, turning all the individual thermostats up, shaking his head and looking puzzled.  

Then we looked at the boiler settings and it's on E ... who put it on that (not me!!) So I ask DH, had he been fiddling with the boiler settings and he admitted he had "turned it up" yesterday afternoon. "So what do you think E stands for darling?" "Um .... excellent? Excessively hot ..." he flounders. It stands for ECONOMY Mr Numpty! 

I think he does have a point in thinking that E is hotter than 5 as it is inbetween 5 and Max but there's a reason we keep the manual right beside the boiler ...