Heating and cooling were 52% of home energy in 2020, so start there

Start with heating and cooling. Space heating and air conditioning were 52% of household energy use in 2020, according to EIA's page on energy use in homes, which draws on its Residential Energy Consumption Survey (RECS 2020); water heating, lighting and refrigeration took 25%, and all other devices 23%. One climate changes the order: in the region RECS 2020 calls hot-humid, air conditioning used 299 trillion Btu and space heating 219, so cooling comes first there (EIA, RECS 2020 table CE3.1). Reading the order costs nothing, and renters and owners can both act on it.

Heating and cooling lead, then hot water, lighting and the fridge

The three shares measure energy, not dollars. Heating and cooling are mostly seasonal and vary with location, home size and the equipment and fuels used, the same EIA page says, while water heating, lighting and refrigeration run all year. RECS 2020 is still the newest end-use data: EIA's RECS page says the full 2024 data set comes out in spring 2027.

On the bill, the gap narrows. Households spent $232.76 billion on home energy in 2020, by RECS 2020 table CE3.6; space heating and air conditioning took $93.55 billion of it, or 40.2%, and appliances, electronics, lighting and other uses $89.61 billion, or 38.5%.

When electricity is your only energy bill, EIA's electricity breakdown gives the order: air conditioning was 19% of residential site electricity in 2020, space heating 12% and water heating 12%, with lighting and refrigerators next.

Space heating alone tops half in the Northeast and Midwest

Where you live moves the order. RECS 2020 table CE3.1 lists each census region's household energy by end use in trillion Btu; each share below is that column divided by the region's total.

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In the Northeast and Midwest, winter heating is where the energy goes; air conditioning was about 5%. In the South, space heating still led every single end use, but the appliances, electronics and lighting grouped as other uses added up to more, 32.4% against 29.1%. The West put the largest share of any region into water heating, 24.5%.

In a hot-humid climate, air conditioning comes first

Of the five climate groups in RECS 2020 table CE3.1, only the hot-humid one used more energy for cooling than for heating.

Example, from EIA's published table. The hot-humid row of table CE3.1 lists 1,306 trillion Btu of household energy for 2020. Air conditioning used 299 trillion Btu: 299 ÷ 1,306 = 22.9%. Space heating used 219: 219 ÷ 1,306 = 16.8%. Together they come to 518 ÷ 1,306 = 39.7%, against 52% nationally, and the table's other column, the appliances, electronics and lighting, took 482 ÷ 1,306 = 36.9%. In dollars the lead is wider: $10.12 billion for air conditioning against $5.02 billion for space heating in table CE3.6.

There, the cooling setting comes first. The devices in the other column also used more than space heating did.

In an apartment, hot water rivals the heat

Apartments flip a different pair. In apartments in buildings with five or more units, RECS 2020 table CE3.1 shows water heating at 230 trillion Btu in 2020 and space heating at 187, out of 769: 29.9% against 24.3%. Across all rented apartments the two were nearly even, 306 and 300 trillion Btu. EIA's homes page gives the reason heating shrinks: apartments are generally smaller than single-family homes and often partly insulated from the weather by the apartments next door.

If the water heater sits in your unit, its setting is the second free change after the thermostat. If one heater serves the whole building, the setting is the landlord's.

Work down the list: thermostat, leaks, hot water, then devices

1. The thermostat, free. DOE's Energy Saver guide (2022) says you can save as much as 10% per year on heating and cooling by turning the thermostat down 7 to 10°F for 8 hours a day in fall and winter, and up in spring and summer; with a heat pump, not without a smart or programmable thermostat designed for heat pumps. The method is in setting back a furnace thermostat.
2. Air leaks, a small buy. The same DOE guide calls caulking, sealing and weatherstripping the openings to the outside one of the quickest money- and energy-saving tasks, and says that by sealing uncontrolled air leaks you can save 10% to 20% on your heating and cooling bills; seal the air leaks first, before any insulation. Renters ask the landlord before caulking.
3. The water heater, free. DOE's guide says to set it to 120°F; check that setting at the tap. On a gas unit, anything past the temperature dial is work for a licensed plumber or gas fitter.
4. Devices, last. The 23% is spread over many devices, so price one by its watts before you replace it.