I'm pretty sure this JavaScript mining executes the Cryptonight algorithm, which is used for Monero mining. I tested it with a 4-th gen Intel Core i5 and it achieves about
60 H/s, which leads to roughly earning 1 satoshi per minute in your FreeBitco account, so unless you have very cheap electricity you will mine at a loss.
This was to be expected from a JavaScript implementation. A native CPU miner is much faster, for example the same processor achieves
130 H/s (i.e. 2 times more) with the
Nicehash miner and currently they pay roughly 2 times more for mining Monero, so currently you will get
4 times more bitcoins mining Monero with
Nicehash using your CPU. If you have a modern graphics card you can earn even more. That's why currently it's better to use
Nicehash for earning Bitcoins and then if you want you can easily deposit them to your FreeBitco.in account for the interest.
The only disadvantage is that Nicehash has a 0.001 BTC minimum payout compared to freebitco.in 0.0003 and if you're already claiming the faucet and have referral income that does not really take long.
On the question of electricity consumption is there any way to calculate how much extra power is being used if you set the mining to use only 10% or 20% etc.? If the computer is being used all day how much extra cost am i incurring by having this in the background?