1. Limit heat generating sources. This one applies to the kettle, shower, hairdryer, oven, heater and any other appliances that involve heating. Up to 80% of your electricity bill can be attributed to appliances that generate heat. So next time you think a 20 minute shower sounds blissfully amazing or leave you hair iron on for 30 minutes before you even use it, be prepared to see an increase in your bill for this indulgence.