Well, your electric bill will definitely go up depending on how big your tank is and the types of pumps and filters that you have. And lights. If you know what you're paying for electricity now, usually you're billed per kilowatt, you can figure out the watts of your tank by just adding up all the parts of your aquarium.
Just make a graph. List all the parts. On the parts themselves they'll tell you the consumption. They'll tell you the volts, the amps, the watts, and with a little bit of math you can figure out how many total watts you're using during the day and how many total watts you're using at night when the lights shut off. And then it's a simple calculation. You have 1,000 watts in a kilowatt, and if you know what you're paying per kilowatt you can figure out what that tank will cost to run.
When I size aquariums for people a lot of times I tell them how many amps or how many watts they're going to be using. We'll spend a little bit more money on more efficient protein skimmers and return pumps so that in end, in the long run, the tank will cost less to operate. Going with LED lights versus T5's or versus metal halides will save you money in the long term because they use less wattage and give you more output per watt. So, spending a little bit more money up front will save you money every month.
Another big contributor to your electric bill is heat. Large tanks need large pumps. They produce a lot of heat, so most people buy chillers for these large tanks. And especially tanks that are not plumbed correctly or use pumps that are not efficient will have to rely on the chiller to keep the water in the proper temperature range or from getting too hot. Chillers are rated by horsepower, third horsepower, half horsepower, and any time you hear horsepower you know it's going to cost you a lot of money on your electric bill.
I've seen tanks cost three or four hundred dollars a month to maintain for large five, six, seven hundred gallon tanks. But a typical tank, ninety to a hundred gallons, should cost no more than thirty to fifty dollars a month if set up correctly.