I make it a habit, to not leave an electric kettle on their base/socket thingummy, after use - that forces me to lift the kettle, and in the process notice how much/little water there is in it, before turning it on.
Neither of my kettles require me to lift them to get water into the cups
I can lift them to fill them, but normally use a jug, the one on left is not as economic as one on right, as it has a bleed back control so it can give a variable amount of water, where one on right is fixed amount, one on left slightly more expensive and I can manually also stop the flow.
I try to keep them reasonably full, I can see no benefit at all in not filling kettles of that type. It does mean to fill my flask I have to boil water into a cup then pour into the flask, but for tea it means water is on the boil when it hits the bag, no need to re-boil.
The other option is these
with a insulated kettle that will keep water warm for 4 hours, they have the advantage when making multi cups of coffee/tea, wall mounted versions go back as far as I can remember, early ones were glass with a whistle and a hose to put on tap to fill them, these progressed to auto fill types with baffles inside to stop water circulating so boiling water remained at the bottom, and they were insulated to keep the water at near boiling temperature, there was also a version which did not water so hot, often a 7 litre tank of water hot enough to wash ones hands.
In last few years I have seen a combination type, which can deliver both hot and boiling water, can't say I trust them.
However in the winter non of them really save energy, they may save money, but we heat our homes, so any heat from ovens, lights, and kettles reduces the amount needs from the central heating, so the heat is not wasted. Only in the summer do we need to reduce the heat which gets into the home, this is when the induction hob comes into its own, but for me in winter it is guess work, as don't know how much energy the central heating is using day to day, the thermostat records how long it runs for to heat the home, but not how much to heat DHW, and smart meters will not help they only do the electric, the oil needs me to open top of tank and look in.