Interesting if you're hosting at home - ok I should perhaps narrow it down further to hosting at home in the UK - and were considering power factor correction capacitors to knock down the electricity costs:
"In a domestic single phase power supply, unlike commerce and industry, you do not pay reactive power charges and you do not have a kVA limit so the only one who would benefit from fitting Power Factor Correction would be the supply company since they would need to supply less "kVA" for a given killowatt consumption.
kW = kVA x pf.
Killowatts are killowatts and the simplest way to save them is to turn things off.
If your machinery is using motors, you may find reducing the voltage to these will save energy especially if they are not fully loaded.
I hope this helps.
Regards"
Really? Running air conditioning or the refrigerator at 120VAC is more energy efficient than running at 126VAC? I suspect not.
Well, I'm only quoting the electricity guy's message to me. England moved from 240v to 230v for residential supplies a few years ago and everything still works just as well on 230 as it did on 240 but just used less electricity doing it. I'm guessing he's alluding to this. Most people here still think it's 240 because that's what they grew up with and they haven't noticed anything different plus the devices invariably say 220-240v on them
Ah, the British Isles. Lots of rain, fog, clouds, and at that time likely, mostly incandescent bulbs. Resistive loads will use less power with lower voltage but motors get more efficient with higher voltages. You would have been turning on lamps earlier than in brighter climes. A few short years ago what was then the largest natural gas electric generating facility in the world came online not far from here. It provides power for a lot of the southeast, Florida, Georgia, South Carolina, Tenn., Alabama. Before it went online I could measure voltage at the wall to be between 126 & 128VAC. Surprised me as it was lower on Long Island where I'm from. Lots of rural homes out here, long lines. The the new electric facility had a different policy. Voltage at the wall went bam smack on 120VAC, maybe up to 122 VAC at times. Overall there had been a trickle up effect, the northern states getting some free power. That stopped. They hustled adjusting voltages mid-summer. Suddenly power lines were falling all over the northeast, particularly Pennsylvania. Up north there they must have seen it was going to be reflected in profits and had no reasonable way to explain it. They must have started lowering their own voltages relative to one another. Lines got hot, stretched, broke and fell. Things that use to work well started drawing more current. Global warming, lots more AC use in the south, think they'd lower their voltages if the AC were going to be costing the customers less? Don't know for sure, this is just my theory.
Perhaps the UK power utility saw what a large fraction of electric usage they had of incandescent lamps and with the low power bulbs coming on the market decided to fudge profits by making electric motors less efficient.