[tl;dr]
Minting on a RaspberryPi is required to increase/keep the level of decentralization!
[/tl;dr]
A RaspberryPi consumes only little energy (typically below 2 Watts), doesn’t heat up your flat and makes no noise. It can be run unattended for months (installation of updates from time to time recommended…).
While the latter arguments are in favour of your comfort (heat, noise), the energy consumption is of economical importance.
There’s a break-even point at which NSR holders have to pay as much money for the electricity to operate a minting device as they earn from minting rewards.
This depends on the price per kWh, the energy consumption of the minting device and the amount of NSR.
Holding a number of NSR at or below that break-even point inhibits minting (bad for the security) and participation (bad for community and development).
While one might be able to change the amount of NSR, the change of price per kWh is limited.
Changing the energy consumption of the minter is an option, though.
A RaspberryPi might change the energy consumption dramatically, because it typically runs at (or below) 2 Watts.
Compare this to a Laptop or a PC.
Arithmetic example:
at 2 Watts a RaspberryPi consumes 17.5 kWh per year. That is a few USD per year even if the electricity is quite expensive (say 0.30 USD/kWh), it’s not much more than 5 USD.
At the current NSR price level you need to mint approximately 60 blocks (at average 5 per month) to cover the electricity costs.
I don’t know how many NSR you need to hold to mint at average 5 blocks per month, but I’m sure it’s way less than you require to cover electricity costs of a PC 
And if you live in an area where electricity is cheaper, you need even less blocks to cover the costs.
In the US prices below 0.10 USD/kWh are no exceptional case.
10 cents per kWh reduces the break-even point (at current NSR price level) to 20 minted blocks per year, or approximately 1.5 per month.
This calculation doesn’t include tha hardare invest of 40 USD for a RaspberryPi.
