Window U-Value Calculator

Compare the energy performance of different window glass types. Enter your climate data and energy rates to see annual heat loss and estimated energy costs for single pane, double pane, low-E, and triple pane windows.

Glass Type

Number of Windows

Avg Window Area (sq ft)

Heating Degree Days

Cooling Degree Days

Energy Pricing (edit to match local rates)

Heating ($/therm)

Cooling ($/kWh)

Best U-Value Option

Triple Pane

U=0.18 / R=5.6

Annual Savings vs Single

$231.06

Single pane costs $279.42/yr

Selected Type Annual Cost

$126.28

$12.63/window across 10 windows

Glass Type	U-Value / R-Value	Annual Energy Cost
Single Pane	U=1.04 / R=1.0	$279.42
Double Pane	U=0.47 / R=2.1	$126.28
Double Pane Low-E	U=0.30 / R=3.3	$80.60
Triple PaneBest value	U=0.18 / R=5.6	$48.36

Most efficient: Triple Pane at $48.36/yrTriple-pane and double-pane Low-E windows dramatically reduce heat transfer compared to single-pane glass. In cold climates (HDD > 6,000), upgrading from single to double Low-E typically pays for itself in 5-10 years through energy savings alone, with additional comfort benefits from reduced drafts and condensation.

This is an estimate based on typical NFRC U-values and simplified degree-day calculations. Actual energy performance depends on window frame material, installation quality, air leakage, solar heat gain coefficient (SHGC), and local climate. Consult a certified energy auditor for precise savings.