210W seems very low, is this calculated or measured at the wall? PSUs have losses, so a 150 Watt video card would be pulling 180 Watts from the wall with an 80% efficient PSU.
If you're using the PC at the same time, are you sure your getting 94.5 MH/s out of it?
If you're not using the PC, do you usually leave it on 24/7 or are you only mining when you turn the PC on? If it's the latter, then your BTC rates per day will be less, if it's the former, then you were pouring money down the drain before you started mining. If the PC is running other services 24/7 then the costs are already incurred, but do these services affect the hash rate. i.e. what is the true cost of mining vs the true profit.
Difficulty is going up by 30% tomorrow, I believe, so your amount of bitcoins will reduce.
Not trying to be negative, but a lot of people are throwing money away in the false illusion that they are making money through mining.
All numbers are measure at the wall socket, and remember that I've underclocked the memory, which removed 30w measured at the wall.
Also, I've got a Core i5, and it underclocks itself when not being used. In addition, I have SSDs as main drives, and only one HDD for storage. So the main energy eater is the card.
And I'm sitting at the computer most of the hours it's on, which is roughly 17-18 hours a day, which I've now complemented with mining during that time. I can't sleep with on anyway as it makes too much noise.
And since it's not on 24/7, I don't run any kind of services on it. Even if I did, they'd be using CPU and not GPU.
When I browse the web, which is what I do the most, the hashrate lowers to 84-87 MH/s when jumping pages or reloading.
The way I see it is, is that as long as I'm doing other stuff on the computer, and I get more bitcoins worth than the electricity costs, I'm doing something useful with my spare processing power.
I do have two 5870 coming that I'm going to mine with. But I didn't buy them just for that though, as I want to upgrade for BF3 etc. Mining only accelerated the purchase.
That I can possible get my money back by mining is icing on the cake that is running the latest games.