Use wisely! How you choose to operate your home has the greatest impact on energy consumption and costs. While these measures may be obvious, they are often overlooked. Sometimes the simplest things are the most effective and can immediately improve energy conservation and lower utility bills.

Curtains, Blinds and Shades

Curtains, blinds and shades can usually be added to the interior of a building without damaging its historic integrity. When properly used, these features can assist historic window systems in providing comfort to the interior. By providing shade from summer heat, these features help further reduce the cooling load, while still permitting daylight. They also diminish heating loads in the winter by acting as partial insulation on the north and northeast sides where the building receives little direct sunlight. To be most effective, interior shades should carefully be fitted to individual windows.
U.S. Department of Energy: Energy Savers: Window Treatments & Coverings

Dennis Knight's "Effective Use of Window Treatments to Help Reduce Your Energy Bill"

How to operate shutters and shades to maximize their benefits:

Summer:
Shutters or shades should be closed on all windows exposed to direct sunlight during the day to shade the window from direct solar heat gain. This typically is the east, south and west facing windows. Once the sun angle has passed the point where the window(s) is no longer exposed to direct sunlight the shutters or shades may be opened to take advantage of indirect daylighting to reduce the need for artificial lighting. North facing windows do not need to be closed during the summer to control solar heat gain and are primarily used for the other features mentioned above. Using shades and shutters in combination will not increase the effectiveness of either device much, if at all.

Winter:
Shutters or shades facing east, south and west should be open during the part of the day when they are exposed to direct sunlight. After the sun has passed an angle where the window no longer receives direct sun the shutters or shades may be closed to help reduce winter heat loss, especially when the daytime temperature is really cold most of the day. Shutters and shades throughout the house on all sides should be closed at night to help to reduce heat loss through the windows.

Artificial Lighting

Designed before the use of artificial lighting, historic buildings relied on windows to provide natural daylighting. Making use of these windows and lessening reliance on artificial light during the day can not only save on electricity, but also help cool the house. Artificial light only generates heat, and thus can unecessarily warm interior spaces and cause an increase in cooling loads. Coal-fired plants power electricity in the U.S. and are responsible for 30 percent of the country's total greenhouse gas emissions. Thus, reducing use of electricity is a priority.
U.S. Department of Energy: Energy Savers: Lighting and Daylighting

Thermostat Settings

Perhaps the most obvious measure to reduce energy consumption in an historic house it to show restraint when it comes to adjusting the thermostat. No historic building will ever be able to provide the consistent level of low temperature that one might find in a modern building. In order to enjoy the beneifts of living in an historic homes, occupants must be prepared to make adjustments to the changing weather as well.

In colder months, humidifiers can be very helpful in reducing heating costs. Particularly when added to a frequently inhabitated room, humidifiers help provide comfort when the thermostat is set at a lower level. Dehumidifiers can also be used to reduce the level of cooling required. When trying to lower energy use, air conditioning should be used at a minimum. Of course, comfort is important, but cheaper alternatives should be put in place first. Attic or windows fans can help with cooling. In warmer months it is most effective to use these in an exhaust capacity. See how you can maximize the features in your house and save on air conditioning costs!

Service Mechanical Equipment

Before jumping to upgrade, improve your existing systems by servicing all mechanical equipment regularly and thoroughly. Change dirty air filters in air-conditioning units and furnaces. Be sure to wrap the distribution lines (ductwork, pipes, etc). with insulation so that the heat and air actually makes it to the living areas and does not simply escape from the pipes on the ride. These things may seem obvious, but if overlooked, they can diminish the energy efficiency of the equipment and cost the owner more energy-related dollars for less output.