Combine circulating fans with room air conditioners for best air distribution throughout the house. Use fluorescent lights where possible. A dripping hot water faucet makes a hot water heater keep working. Utilize working shutters, interior or exterior, to control heat gain or loss. Close off unused rooms.
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Clean the heat reflector below the hot water heating element. It will reflect heat better. Install a flow-restrictor pipe to the shower head. It's inexpensive, threads into the pipe and restricts the flow of water by several gallons of water per minute. Don't overload appliances that use hot water, such as clothes and dishwashers.