A 21 kWh/month it's 252 kwh/annum (I guess?), which is around energy label E in the new EU energy labels.
If you go for energy label A, some fridges have 101 kWh/annum, which is more than half less! I haven't seen many, and they are usually very tall, but hopefully we can see more and more in the future.
They're freaking expensive, though. I just replaced a (probably) 25 year old fridge by one with a D label. The difference with a C or E label is small in energy use. I do notice that the exterior gets really less warm than the old model. I don't think it would have qualified as an E.
BTW, if I'm not mistaken, the energy label depends on the function. So 250kWh/yr could be (much) lower than E when the volume is smaller.
If you go for energy label A, some fridges have 101 kWh/annum, which is more than half less! I haven't seen many, and they are usually very tall, but hopefully we can see more and more in the future.