Welp, that depends on where you live and how much you pay for electricity.
Anyhow, here is the power consumption for my tank (300L):
Filter (1400L/H): 35W
Lighting (91cm Glopower bulbs): 2x30W
Wavemaker: 6W
Heater: 75W (It is recommended to use 2 heaters in bigger tanks, but mine does fine with one.)
All together: 176W
And that would be it for power. If you buy something like the Juwel RIO 240, which comes with all the gear,
here is your power consumption:
Bioflow 3 filter: 6.5W
Light Unit: 2x High-Lite 120 cm 54 W
Heater: 200W
Pump: Juwel Ecoflow 6.5W
All together: 321W
Now, for water. (If you change about 25% of water every third weak)
Lets take a tank with the size 100*50*50 cm's (250L). The gravel is 3 cm's thick. There are ornaments at the size of 12 dm[sup]3. [/sup](about the size of 20cm*30cm*20cm, like a solid block)
Now. With this setup, there is about 233 liters of water in the tank. 25% of that is 58.25 liters.
For water changes, that would give you: ~1010 liters of water every year, if we change the water every three weeks.
Calculate from there, my friend. It all depends on how much you pay for electricity and other.
Snoop around, and see what you can find. As you can see, my power consumption is 54% lower that the Juwel RIO 240. So there is a chance that you can skimp out on the price of stuff if you choose your equipment.