The power or meter box as well as the circuit breaker panel is only a problem if you get magnetic fields of it. Those you CANNOT shield against with shielding paint. If the power/meter box has a smart meter in it, then you can shield against that with shielding paint, but you want to cover a decent area like 4 square meters / 40 sqft behind the smart meter.
To know if your electrical box makes a magnetic field, you need a triple axis gauss meter and I’d recommend the TF2 you find in our store. It’s a reliable unit in a strong housing which also covers RF radiation up to a wide range including 5G Tower-to-phone frequencies. When you have your gauss meter you want to measure at a distance from the electrical box where someone might sit or sleep. If readings are higher than 0.3mG (or 30nT) then they are not ideal. At 1mG (100nT) research shows links to health issues and so this should be avoided with a nice margin.
Magnetic fields vary in strength depending on the usage of electricity, so ask someone to start a hair drying somewhere in the house and this will increase usage and possible magnetic fields… then you take your measurements.
You may find that the wall the power/meter box is on, is unusable to park a bed or chair against, but the other side of the room can be perfectly acceptable. If there is a smart meter, you should shield against that, BUY NEVER shield just one wall in a bedroom as it will reduce RF from the smart meter, but will also reflect back to you the RF hitting it from your side of the wall (phone towers, wifi from neighbours, other smart meters) so you’d get them twice. Always shield bedrooms completely with T98 Shielding Paint, including walls, ceiling and the floor should ideally be done as well if it is not on ground floor or you have wiring running underneath.
Of course the shielding of a room is not complete without taking care of the windows. For that you use NOVA shielding paint.