Yup - you are 100% correct. Power costs about NZD$0.22 per kWh when weight averaging the day and night rates. This means I use:

18KW * 24h/day * NZD$0.22 = NZD$95/day

Meanwhile, I could sell the Gridcoin for about NZD$0.04 per coin, so I earn about:

800 GRC/day * NZD$0.04/GRC = NZD$32/day

That being said, recently GRC traded for almost NZD$0.15 at one point, which would have yielded NZD$120/day.

In reality, there are still several reason I continue doing this:

• I need the hardware for my research anyway, and this is running on idle cycles. The power bill of using those cycles is only a fraction of the total compute powerbill.

• The price of GRC will go up, so I will see a good return in future if I were to sell

• I have plans to use the GRC I mine on idle cycles to commission compute in the future through the BOINC and GRC network, if I can overcome the technical hurdles of the models I work with.