Datalizer Energy Operating Cost Calculator for TVA

<< >>
This rectangular white cardboard rule has four slides and is held together with ten metal rivets. The top two slides are used to calculate the annual operating cost of a natural gas furnace, while the bottom two slides perform the same calculation for an electric heat pump. Tables on the back of the instrument give values for building heat loss, typical heating system efficiencies, and heating load hours for the states covered by the Tennessee Valley Authority: Alabama, Georgia, Kentucky, Mississippi, North Carolina, and Tennessee. A sample calculation is also provided on the back.
The front and back are both marked: Electricity (/) THE POWER (/) OF CHOICE. Both sides are also marked: TVA. The rule thus advertised TVA's ability to supply inexpensive public electric power and promote energy conservation. The back bottom left corner is marked: © 1990 Datalizer Slide Charts, Inc., Addison, IL 60101. A former employee of the Perrygraf (or Perry Graf) Corporation (see 1979.3074.03) established Datalizer around 1960, and the company remained in business as of 2012.
References: "From the New Deal to a New Century," Tennessee Valley Authority,; "Slide Chart Specialists," Datalizer Slide Charts,
Currently not on view
date made
Datalizer Slide Charts, Incorporated
place made
United States: Illinois, Addison
Physical Description
paper (overall material)
metal (part material)
overall: .2 cm x 23.9 cm x 12.5 cm; 3/32 in x 9 13/32 in x 4 29/32 in
ID Number
nonaccession number
catalog number
Credit Line
Gift of Jack Warner
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History


Add a comment about this object