Currently, I have one graphics card doing mining.
If I add a second graphics card, is there much of an electricity savings?
Your electricity consumption will increase, however this can be a misleading indicator of profitability since you
can still make more profit with 2 GPUs.
Lets simplify it a bit. The electricity consumption can be represented as a result from 2 different sources,
Let's say that the GPU uses 100W and the rest of the system 250W, summing at 350W. Now, if you add a second GPU, the system will still use 250W, however you will have 2x100W for the 2 GPUs. Hence the overall power consumption is 250+(2x100)=450W. So you have increased your power consumption by 100W, however, if you look at the "useless" consumption - everything apart from the GPUs can be considered useless, as you are only running them so that the GPU runs and mines you coins - percentage wise it only makes up 56% compared to 71% before. Hence you are wasting less power with 2 cards than with one.
Looking at the overall increase in power consumption, using a second (identical) GPU doubles your income, but your electricity consumption has only increased by ~30%.
Please note that this was only a simplified example to explain how your profit and electricity consumption would change. In order to calculate this for your own situation, you have to know
exactly the power consumption of your system and that of your GPUs. Please calculate it accurately before investing.
