How many months of bills do I need to build an energy baseline?

Twelve is ideal because a full year captures both the heating season and the cooling season, which is where most household energy variation lives. If you do not have twelve months, start with what you have. Even three to six months shows patterns. The key is tracking kilowatt-hours and therms, not just dollar amounts, because rates change and billing periods vary. Once you have a year, you can compare any month to the same month last year and spot real changes in consumption.

What uses the most energy in a typical U.S. home?

According to the EIA, heating and cooling account for roughly half of residential energy use. Water heating is the second largest category, followed by appliances (refrigerator, washer, dryer, dishwasher), lighting, and electronics. However, the honest answer is that national averages may not match your home. A household in the South with electric heating and air conditioning will have a different profile than a home in the Northeast with a gas furnace and no central air. The baseline exercise shows you your own breakdown, which is more useful than any average.

What is a phantom load and how much does it cost?

A phantom load, also called standby power or vampire draw, is electricity consumed by devices that are plugged in but not actively in use. Cable boxes, game consoles, phone chargers, printers, and smart speakers all draw small amounts of power continuously. The DOE estimates that phantom loads can account for 5 to 10 percent of a household's electricity use. A plug-in energy meter like the Kill A Watt can measure the draw of any individual device. Smart power strips that cut power to idle devices can reduce phantom loads without unplugging everything manually.

My bill went up but I did not change anything. What happened?

There are three common causes. First, the rate changed. Electricity rates in the U.S. have risen roughly 30 percent since 2019, so the same kilowatt-hours cost more. Compare kWh, not dollars, to see whether you actually used more energy. Second, the weather was more extreme. A hotter summer or colder winter drives heating and cooling loads higher. Compare your usage to the same month in a previous year. Third, something changed in the house without your noticing: a failing appliance running longer cycles, a stuck HVAC damper, a water heater element degrading, or a new device drawing more than expected.

Should I hire a professional energy auditor?

A professional energy audit is worth it if your baseline shows consistently high usage that you cannot explain, if you are planning major improvements like insulation, windows, or HVAC replacement, or if you want to qualify for utility rebates or tax credits that require an audit. A professional audit typically includes a blower door test to measure air leakage, an infrared camera scan to find insulation gaps, and duct leakage testing. Costs range from $200 to $600 depending on home size. Many utilities offer subsidized or free audits. Check with your utility before paying full price.

Building an Energy-Use Baseline: Know Where Your Energy Goes

The Concept

A year of use, in one view

A baseline is your own energy consumption recorded month by month for a full year. It is not a budget, a goal, or a plan. It is a measurement. Once it exists, you stop reacting to a single high bill and start seeing the pattern underneath it: which months cost the most, why, and whether anything changed from one year to the next.

Most households have two energy streams: electricity (measured in kilowatt-hours, kWh) and a heating fuel (natural gas measured in therms or CCF, propane in gallons, heating oil in gallons). Some homes are all-electric. A complete baseline tracks every energy source your home uses.

The average U.S. home uses about 865 kWh of electricity per month, roughly 10,400 kWh per year.^[1] But that national average folds together a 500 kWh apartment in Maine and a 1,400 kWh house in Louisiana. Your number is what matters, and you find it by building the baseline.

Why this matters for preparedness

Knowing your baseline means knowing your loads. Knowing your loads means knowing what size generator you need, how long a battery backup will last, and which circuits matter most during an outage. The baseline is the first step toward both conservation and backup power planning.

Before You Start

How to read your utility bill

The baseline starts with your bills, but you need to know what to pull from them. The dollar amount is the least useful number on the page. The energy consumed is what matters.

Kilowatt-hours (kWh), not dollars

Track kWh consumed, not the dollar total. Electricity rates have risen roughly 30 percent since 2019, from about 13.7 cents per kWh in 2019 to over 17 cents in 2025.^[2] If your bill went up but your kWh stayed flat, the rate did the work, not your usage. Comparing dollars year-over-year will fool you. Comparing kWh will not.

Billing period dates and days

Billing periods are rarely exactly 30 days. A 35-day billing period will show higher usage than a 28-day period even if your daily consumption is identical. Some bills include "average daily usage" which normalizes this for you. If yours does not, divide kWh by the number of days in the billing period to get your daily average for that month.

Rate tiers and time-of-use

Some utilities charge a flat rate per kWh. Others use tiered pricing (a lower rate for the first block of kWh, a higher rate above that) or time-of-use rates (higher during peak afternoon hours, lower at night). Know which structure your utility uses because it affects both your bill and your conservation strategy.

Our reading your utility bill guide covers rate structures, fees, and charges in detail.

Gas bills: therms or CCF

If your home uses natural gas, your gas bill reports usage in therms (100,000 BTUs) or CCF (100 cubic feet). Track whichever unit your utility uses. One therm is roughly equivalent to 1.037 CCF. Gas usage is almost entirely seasonal: heating, water heating, and cooking. A home with gas heat will show a dramatic difference between summer and winter gas bills.

Build It

Twelve rows, one page

Gather twelve months of utility bills (check your utility's online portal for historical data if you do not have paper copies). Fill one row per month. A notebook, a spreadsheet, or a printed worksheet all work.

Month	Electric kWh	Electric $	Gas therms	Gas $	Days	Notes
Jan	1,120	$178	95	$112	31	Cold snap week 2
Feb	980	$156	82	$97	28
Mar	780	$124	55	$68	32	Shoulder month
Apr through Nov: fill from your bills
Dec	1,050	$167	88	$104	30	Guests week 4

What to record

Electric kWh. The number consumed, not the dollar amount. This is the core metric.
Gas therms or CCF. If you use natural gas. Skip this column if you are all-electric.
Dollar amounts for each. Useful for cost tracking but secondary to consumption.
Billing days. Normalizes the comparison between months.
Notes. This is the column that makes the baseline useful. Record anything that changed: a heat wave, a week of guests, a new appliance, a vacation, a rate change. When you look at the baseline six months later, the notes tell you why a number is higher or lower than expected.

If you use propane or heating oil

Add a column for gallons delivered and cost. Propane and oil are delivered in bulk, not continuously metered, so your "monthly" usage is an estimate between deliveries. Track delivery dates, gallons, and price per gallon. Over a year, the total gallons divided by 12 gives you a monthly average. The heating months will be well above that average and the summer months well below.

Reading the Pattern

What the seasonal pattern tells you

Once you have twelve months, a shape appears. Most homes show a U-shape or a W-shape: high in winter (heating), low in shoulder months (spring, fall), and high again in summer (cooling). The depth of the valley and the height of the peaks tell you how much of your energy use is weather-driven versus constant.

The base load

Your lowest month is close to your base load: the energy your home uses regardless of weather. Refrigerator, water heater, lighting, electronics, and phantom loads. This floor is the most consistent part of your usage and the easiest to compare year-over-year.

The heating bump

The difference between your lowest month and your highest winter month is mostly heating. If you heat with gas, the bump shows on the gas bill. If you heat with a heat pump or electric furnace, it shows on the electric bill. This is typically the largest single energy cost in a home.

The cooling bump

The difference between your lowest month and your highest summer month is mostly cooling. In the Southeast and Southwest, this bump can exceed the heating bump. Air conditioning is always electric, so the summer peak always shows on the electric bill regardless of heating fuel.

If your lowest month is still high compared to similar homes, the base load is where the waste is. If the peaks are extreme but the valleys are low, the waste is in heating, cooling, or the building envelope (insulation, air sealing, windows). The pattern tells you where to look.

Major Loads

Where the energy actually goes

The EIA breaks residential energy use into categories. Knowing these helps you interpret your baseline and decide where to focus.^[1]

~50%

Heating and cooling

The largest category in most homes. Driven by climate, building envelope quality, thermostat settings, and equipment efficiency. This is where insulation, air sealing, and thermostat management have the biggest impact.

~15%

Water heating

The second largest category. A conventional tank water heater runs 24 hours a day to keep 40 to 80 gallons hot. Reducing hot water temperature from 140 to 120 degrees saves energy and reduces scald risk without affecting comfort for most households.

~15%

Appliances

Refrigerator, clothes dryer, washer, dishwasher, and oven. The refrigerator runs continuously and is typically the largest single appliance load. An older refrigerator (15+ years) may use twice the electricity of a current model.

~10%

Lighting

LED bulbs use 75 percent less energy than incandescent bulbs and last 25 times longer. If your home still has incandescent or halogen bulbs, replacing them is the single fastest return-on-investment energy improvement. One bulb at a time is fine.

~5-10%

Electronics and phantom loads

TVs, computers, game consoles, cable boxes, routers, chargers, and smart devices. Many draw power even when "off." The DOE estimates phantom loads account for 5 to 10 percent of residential electricity use. A plug-in energy meter (like the Kill A Watt) reveals exactly how much each device draws.

Varies

Envelope losses

Air leaks, thin insulation, and single-pane windows do not show up as a separate line item. They amplify the heating and cooling load. A home with poor air sealing forces the HVAC system to work harder to maintain temperature, increasing the seasonal peaks on your baseline.

Going Deeper

Smart-meter data and plug-in monitors

Many modern electric meters record usage in 15-minute or hourly intervals. If your utility makes this data available through its web portal or app, it turns the monthly baseline into a daily or even hourly picture. You can see exactly when your usage spikes and correlate it with what was running at that time.

What smart-meter data shows you

A daily view reveals patterns that monthly totals hide. You might find that your usage is flat on workdays but spikes on weekends (when you are home). Or that a spike happens at 3 AM every night (a failing appliance, a pool pump, or an electric water heater recovering). These patterns are invisible in monthly data.

Check your utility's website for "green button data," "my usage," or "energy usage history." Some utilities offer downloadable CSV files that you can chart in a spreadsheet.

Plug-in energy monitors

A plug-in energy meter like the Kill A Watt measures the actual draw of any device plugged into a standard outlet. Plug it between the wall and the device, and it displays watts, kWh over time, and cost at your rate. Use it to measure:

The actual draw of your refrigerator over 24 hours (typically 1 to 2 kWh per day for a modern unit, 3 to 5 for an older one).
Phantom loads from entertainment systems, cable boxes, and chargers left plugged in.
Whether a dehumidifier, space heater, or window AC is costing more than you expected.

Whole-house energy monitors

Devices like the Emporia Vue or Sense attach to your electrical panel and monitor every circuit in real time. They can identify individual appliances by their electrical signature and show you exactly what is drawing power at any moment. These are more expensive ($100 to $300) and require installation at the breaker panel, but they provide the most complete picture of household energy use.

Action Steps

Cheapest moves come first

The instinct after building a baseline is to buy something more efficient. Resist that until you have done the cheaper work. The order of operations matters because the free and low-cost steps often reduce usage enough to change the math on the bigger purchases.

01

Find and fix the abnormal

Look for months that are significantly higher than the same month last year without a clear reason. A sudden jump with no weather explanation often points to a failing appliance, a stuck relay, or a running toilet (water heater working harder). Investigate before optimizing.

02

Eliminate phantom loads

Use a plug-in meter to identify devices drawing power when idle. A cable box can draw 20 to 35 watts continuously. A game console in standby draws 10 to 15 watts. Put entertainment systems on a smart power strip that cuts power when the TV is off. Unplug chargers not in use.

03

Maintain what you have

Change HVAC filters monthly during heavy-use seasons. Clear the outdoor condenser unit. Clean refrigerator coils. These maintenance tasks cost nothing and prevent the gradual efficiency loss that inflates your baseline over time. Our heating and cooling systems guide covers the full maintenance schedule.

04

Adjust thermostat settings

ENERGY STAR recommends setting your thermostat to 68 degrees in winter when you are home and lower when you are away or asleep, and 78 degrees in summer when you are home and higher when you are away. Each degree of adjustment saves roughly 1 to 3 percent on heating and cooling costs. A programmable or smart thermostat automates this without requiring daily attention.

05

Seal obvious air leaks

Weatherstripping around doors, caulk around windows, and foam sealant around pipe and wire penetrations. These are inexpensive materials with immediate impact on heating and cooling efficiency. On a windy day, hold your hand near door and window edges to feel drafts. That is conditioned air leaving your house and unconditioned air entering.

06

Then consider equipment upgrades

After the free and low-cost steps, the baseline will look different. Now evaluate whether a new appliance, insulation upgrade, or HVAC replacement makes financial sense. The payback period calculation is more accurate when you have already captured the easy savings.

Going Further

When to call a professional auditor

A professional energy audit goes beyond what you can do with bills and a plug-in meter. An auditor brings diagnostic tools that reveal problems invisible to the homeowner.

Blower door test

A calibrated fan mounted in an exterior door depressurizes the house and measures the total air leakage. The result, expressed in air changes per hour (ACH50), tells you how leaky your building envelope is and whether air sealing will make a meaningful difference.

Infrared camera scan

A thermal imaging camera shows temperature differences on walls, ceilings, and floors. Missing insulation, air leaks around windows, and thermal bridging through framing are clearly visible. This is the fastest way to find the specific locations where heat is escaping.

Duct leakage testing

If your home has forced-air heating and cooling, the auditor may test the ductwork for leaks. Leaky ducts in unconditioned spaces (attics, crawl spaces) can waste 20 to 30 percent of the air the system moves, according to ENERGY STAR.

A professional audit typically costs $200 to $600 depending on home size. Many utilities offer subsidized or free audits as part of their efficiency programs. Some rebate and tax credit programs require a professional audit before you can qualify. Check with your utility before paying full price.

Look for auditors certified by the Building Performance Institute (BPI) or RESNET. Certification means the auditor has been trained and tested on diagnostic procedures and building science.

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