A heating-season log: heating input, indoor temperature and degree days on one timeline

Goal

Produce a season-long record in which the heating input sits next to indoor temperature, setpoint changes and outdoor temperature, so that a change in consumption can be matched to weather or to a logged event.

Prerequisites

One heating input quantity the household can read without touching the installation: a heat meter, a gas or oil meter, the electricity meter of a heating circuit, or the runtime hours a thermostat displays. State which one, its unit (NIST SP 811 lists the kilowatt hour among the energy units) and whether it is cumulative. One indoor thermometer at a fixed position, as in the indoor temperature and humidity protocol. A source of daily outdoor high and low: a shaded home sensor or the nearest official station.

Steps

1. Write a header: input quantity, unit, resolution, cumulative or per-interval, indoor sensor position, outdoor source, and the degree-day base of step 4.
2. Read the heating input daily or weekly at one fixed time (for example 07:00) and log date, time and the reading as displayed. Consumption is the difference between consecutive readings, kept in a separate column.
3. Log the indoor temperature from the fixed sensor at the same time. Whenever the thermostat setpoint or schedule changes, log the new value with the time of change.
4. Log the outdoor daily high and low. The National Weather Service defines degree days from the daily mean (high plus low divided by two) and a base of 65 °F; when the mean is below the base, heating degree days are the base minus the mean. A household may use the same construction with a base in °C, but must state it. Store high, low and heating degree days as three columns.
5. Keep a conditions column: days away, guests, airing, a boiler service, a moved or replaced sensor.
6. At month end, write one summary row: consumption, sum of heating degree days, mean indoor temperature, and consumption divided by degree days. Keep the daily rows.

Expected result

A table in which a month with higher consumption can be checked against its degree days and setpoint changes before anything is concluded, and in which two seasons or two dwellings can be compared per degree day once both use the same base.

Limits and test basis

Proposed protocol; the 65 °F base is a convention of the cited page, not a physical constant, and ratios computed with different bases are not comparable. A whole-house gas or electricity meter includes hot water and cooking unless a separate circuit is metered. The protocol is reading and writing only; no adjustment to the installation and no comfort or saving target is part of it.

Base load and the degree-day ratio

A whole-house meter includes hot water and cooking, which do not follow the weather. Consumption divided by degree days therefore rises in mild months, when the base load dominates the small denominator, and falls in cold months, so the ratio is not comparable between months or dwellings. Use the ratio only for a separately metered heating circuit. For a shared meter, plot weekly consumption against weekly heating degree days for the season and fit a straight line: the slope is the response to weather and the intercept is the weekly base load, and each can be compared between seasons or dwellings that use the same degree-day base. Weekly sums also remove the day-boundary mismatch between a 07:00 meter reading and a station's climatological day.