# K-factor

By Nick Bruzzi · Published 2026-07-08 · https://heatprice.com/glossary/k-factor

A home's fuel-efficiency constant used to run automatic delivery: the number of heating degree days that pass per gallon of oil it burns (degree days ÷ gallons used), typically ~3 to 30+ depending on size, insulation, and system efficiency.

It's the "miles per gallon" of your heat — a dealer multiplies your k-factor by your usable tank gallons to predict how many accumulated degree days mean you're due for a refill, so a lower k-factor (more oil per degree day) means more frequent deliveries.

Source: standard heating-oil-industry operational practice (HDD-per-gallon consumption constant).

## See also

- [best time to buy](https://heatprice.com/guides/best-time-to-buy-heating-oil)
- [Heating degree day (HDD)](https://heatprice.com/glossary/heating-degree-day)
- [Automatic delivery](https://heatprice.com/glossary/automatic-delivery)

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