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Safety note: This is general information, not professional advice. Any connection to your home’s wiring must be made by a licensed electrician using a transfer switch or interlock; never backfeed through an outlet. Run generators outdoors only, at least 20 feet from the house, and keep working CO alarms inside. See our disclaimer.
The average US home uses roughly 28 to 30 kWh of electricity per day, or about 10,400 to 10,800 kWh per year, based on recent US Energy Information Administration (EIA) residential averages (the figure shifts slightly year to year and counts electricity purchased from the utility). Your own number can be far lower or higher: climate, home size, and whether you heat and cook with electricity or gas can swing daily use from under 15 kWh to well over 60 kWh. For outage planning, the more useful figure is usually much smaller, because running only the essentials (fridge, furnace blower, sump pump, lights, internet) often lands somewhere around 5 to 12 kWh per day.
Below: how to find and measure your real usage, a worked essentials example, and how it translates into battery capacity or generator fuel. Product details are based on manufacturer specifications from each Amazon listing.
Watts vs kWh: The Two Numbers That Matter
- Watts (W) are power, the rate of use at a given moment. They decide whether a battery’s inverter or a generator can run a load at all.
- Kilowatt-hours (kWh) are energy, power multiplied by time. A 100-watt load running for 10 hours uses 1,000 watt-hours, or 1 kWh. Energy decides how long a battery lasts or how much fuel a generator burns.
Battery capacity is rated in watt-hours (Wh) or kWh, and output in watts. A power station can have plenty of capacity but not enough output to start a well pump, or plenty of output but not enough capacity to last the night.
How Many kWh a House Uses
Typical ranges
| Scenario | Approximate daily use | What drives it |
|---|---|---|
| US average home (EIA, approximate) | 28 to 30 kWh | All loads, averaged across climates and seasons |
| Smaller home or apartment, gas heat | Often 10 to 20 kWh | Lighting, appliances, electronics |
| Larger home with central air in summer | Often 40 to 60+ kWh | Air conditioning runtime |
| All-electric home in a cold climate, winter | Can exceed 60 to 100 kWh | Electric resistance heat or heat pump, electric water heating |
| Essentials-only during an outage, gas heat | Roughly 5 to 12 kWh | Fridge, furnace blower, pumps, lights, internet |
These are broad estimates; plan from your own numbers.
Why essentials-only is so much smaller
The biggest everyday loads are heating, cooling, water heating, clothes drying and cooking. During an outage most households can do without the dryer, oven, and air conditioning, and a gas furnace or gas water heater needs only a small amount of electricity for controls and fans. Electric heat is the exception: if your home heats with electric baseboards, an electric furnace or a heat pump, covering heat in winter takes far more energy than a portable battery can store.
How to Find Your Own Usage
Read your bill
Your electric bill lists the kWh used during the billing period. Divide by the number of days in the period to get kWh per day. Check a full year of history, since winter and summer can differ by two to three times. Plan your backup around the season when outages are most likely and loads are highest; for cold-climate homes that is usually winter.
Use your utility’s smart-meter data
Many US and Canadian utilities with smart meters let you download hourly or 15-minute interval data from your online account, often through a “Green Button” download. Hourly data shows two useful things: your overnight baseline (the always-on loads like the fridge, internet equipment and standby electronics) and your peak hours. The baseline is a good starting point for an essentials estimate, since it is close to what keeps running during an outage.
Measure individual plug-in appliances
For anything that plugs into a standard 120V outlet, a plug-in meter gives a direct kWh reading. Plug the meter into the wall, plug the appliance into the meter, and leave it for at least 24 hours (longer for a fridge or freezer, whose compressor cycles). Divide the kWh reading by the hours metered and multiply by 24 for a daily estimate.
Measure whole-home and circuit loads
Hardwired loads like a furnace blower, a 240V well pump or a sump pump on its own circuit cannot be measured with a plug-in meter. A panel-mounted energy monitor uses clamp-on current sensors around the main feeds and individual circuit wires to track usage by circuit. Installing sensors inside an electrical panel means working near energized conductors, so have a licensed electrician do it.
Measuring Tools Compared
| Tool | What it measures | Key listed specs | Installation |
|---|---|---|---|
| P3 Kill A Watt P4400 | One plug-in appliance | Cumulative kWh on LCD; designed for 115V AC appliances | Plugs into an outlet |
| Emporia Vue 3 | Whole home plus circuits, solar/net metering | ±2% accuracy; minute data kept 7 days, hourly data kept indefinitely; 2.4 GHz Wi-Fi | Inside the panel; licensed electrician |
| Refoss EM16P | Whole home (2 mains) plus 16 circuits | ±1% accuracy (±2% at low current); local data, Home Assistant, MQTT; daily data stored up to 5 years | Inside the panel; licensed electrician |
The Measuring Tools
P3 Kill A Watt P4400: Simplest single-appliance meter
- Choose from the Kill-a-Watt's four settings to monitor your electrical usage
- Monitor your electrical usage by day, week, month, or year
- Electricity usage monitor connects to appliances and assesses efficiency
The Kill A Watt sits between an outlet and an appliance and counts consumption in kilowatt-hours on a large LCD. It can project usage by day, week, month or year. It is designed for 115V AC plug-in appliances and the listing notes it is compatible with inverters, so it can also be used on a power station’s AC outlet to see what a load actually draws from the battery. It cannot measure 240V or hardwired equipment. Check the manufacturer’s maximum current rating (meters of this type are commonly rated 15A, about 1,800W) and keep loads below it. Use it on the fridge, freezer, internet equipment and CPAP.
Emporia Vue 3: Whole-home monitor with cloud app
- SAFETY YOU CAN TRUST WITH UL CERTIFICATION: With Emporia Energy, your home energy monitoring is safe, reliable, and certified. The…
- INSTALLS IN CIRCUIT PANEL of most homes with clamp-on sensors. Supports Single phase, Single-split phase, and 2-wire systems. 3-wi…
- 24/7 ENERGY MANAGEMENT AND MONITORING: Automate, manage and control your home's real power anywhere, anytime to prevent costly rep…
The Vue 3 installs in the circuit panel with clamp-on sensors and reports real-time and historical usage through the Emporia app. The listing gives ±2% accuracy and describes support for single-phase and split-phase systems, which covers most North American homes. It needs 2.4 GHz Wi-Fi with internet. One-second data is shown live in the app, one-minute data is kept for 7 days, and hourly data is kept indefinitely and can be exported. It is UL Listed per the listing. Panel installation should be done by a licensed electrician.
Refoss EM16P: Local-data monitor with 16 circuit sensors
- EM16P MODEL & LOCAL CONTROL & DATA PRIVACY: Access your home energy monitor data locally via Built-in Web UI, Open API, and MQTT w…
- NATIVE HOME ASSISTANT & OPENCLAW AI: Experience seamless Native Home Assistant integration right out of the box—no firmware flashi…
- MAXIMIZE SOLAR & ZERO FEED-IN AUTOMATION: Designed for solar homes, the power monitor works with the Refoss app and Home Assistant…
The EM16P supports two main sensors (2 to 200A each) and sixteen branch sensors (1 to 60A each), which lets you see usage for individual circuits such as the furnace, well pump and sump pump. The listing gives ±1% accuracy (±2% at low current) and stores daily data for up to 5 years with export. Its main difference is local access: a built-in web interface, open API, MQTT and native Home Assistant integration, without relying on cloud services. It is listed as ETL certified to UL 61010 safety standards. Clamp-on installation still happens inside the panel, so use a licensed electrician.
Running Watts vs Starting Watts
Motors draw a surge for a fraction of a second to a few seconds when they start, often two to three times their running watts. Refrigerator compressors, furnace blowers, sump pumps and well pumps all do this. Your battery inverter or generator must handle the largest starting surge on top of whatever else is already running.
Because the surge is brief, it barely changes your kWh total; it matters for output capacity: a 3,600W power station may run a well pump’s 1,000 running watts easily but trip on a 3,000W start if the fridge and furnace are running at the same moment. Check the appliance nameplate or manual for locked-rotor or starting current, and ask your electrician or pump installer if the figure is not listed.
Worked Example: Essentials for One Winter Day
The figures below are illustrative estimates for a gas-heated home on a well in a cold climate. Your appliances will differ, so replace each line with your own measured or nameplate numbers.
| Load (estimate) | Running watts (estimate) | Hours per day (estimate) | kWh per day (estimate) |
|---|---|---|---|
| Refrigerator (compressor cycling) | about 60 average over the day (roughly 150 while the compressor runs) | 24 (cycling) | about 1.5 |
| Gas furnace blower and controls | about 400 | 10 (cold day) | about 4.0 |
| Sump pump (1/2 hp) | about 800 | 1 (total run time) | about 0.8 |
| LED lighting (10 bulbs at 10W) | 100 | 5 | about 0.5 |
| Modem and router | about 20 | 24 | about 0.5 |
| Phones, laptop charging | varies | varies | about 0.3 |
| Well pump (240V) | about 1,000 | 1 (total run time) | about 1.0 |
| Total | about 8.6 kWh |
Two takeaways. First, the furnace blower is the biggest essential load in winter, so a high-efficiency ECM blower or a milder day can change the total a lot; measuring it on its circuit with a panel monitor is worth it. Second, peak output still matters: if the well pump starts while the furnace and fridge are running, the backup source needs to cover roughly 400 + 150 + a well-pump start of perhaps 2,000 to 3,000 watts. Our guide to running a gas furnace on a power station covers the furnace side in more detail.
Turning kWh Into Battery Capacity
A battery’s rated capacity is not all usable. Converting stored DC energy to household AC through the inverter loses some energy, and power stations draw a little to run themselves. As a rule of thumb, plan on roughly 85 to 90 percent of rated capacity being available as AC power. Cold batteries also deliver less, and lithium iron phosphate (LFP) batteries generally should not be charged below freezing, so keep a power station in a heated space.
Jackery HomePower 3600 Plus: 3,584 Wh, 240V in parallel
- Essential Home Backup: The Jackery HomePower 3600 Plus delivers 3600W output (7200W in parallel) to run pumps, heaters, and dryers…
- Safe Power That Lasts: Built with high-temp resistant ceramic membrane battery cells tested at 302 °F, the Jackery HomePower 3600 …
- Plug-and-Play: With its easy plug-and-play design, the Jackery HomePower 3600 Plus, paired with MTS, powers your home effortlessly…
The listing gives 3,584 Wh of capacity and 3,600W of output, with 7,200W and 120V/240V when two units run in parallel. Capacity expands to 21 kWh per unit with extra batteries, or 43 kWh with multiple units. At 85 to 90 percent usable, one unit delivers roughly 3.0 to 3.2 kWh of AC power, a little over a third of the 8.6 kWh example day. It also cites 6,000 cycles, operation in -4°F conditions, and a full recharge in about 2 hours on combined AC and DC input, 2.5 hours from AC or a gas generator, or 4 hours from solar. The listing calls it plug-and-play with its manual transfer switch (MTS) and says no complex installation is required; regardless, connecting any battery to home circuits still requires a licensed electrician and code-compliant transfer equipment.
EcoFlow DELTA Pro: 3,600 Wh, expandable to 25 kWh
- Large Capacity. Featuring a 3600Wh LFP battery capacity, DELTA Pro provides strong electrical storage for home battery backup powe…
- Maximum Output Flexibility. A single DELTA Pro unit packs a 3600W AC output, which can be expanded up to 4500W with X-Boost techno…
- X-Stream Fast Charging. Fully recharge the lifepo4 battery in 1.8 hrs with 240V outlets(3000W), 2.7 hrs with 1800W wall outlets or…
The DELTA Pro lists a 3,600 Wh LFP battery with 3,600W of 120V AC output, or 4,500W with X-Boost, and 7,200W when two units are paired. Usable AC energy at 85 to 90 percent is again roughly 3.1 to 3.2 kWh. Capacity expands to 25 kWh with extra batteries or EcoFlow’s smart generators. The listing gives recharge times of 1.8 hours from a 240V outlet, 2.7 hours from a standard wall outlet, and 2.8 hours from four 400W solar panels, plus EV-station and car charging. X-Boost-style modes typically work by lowering voltage for resistive loads, so do not count on that figure for motors like a well pump. The listing describes 120V output for a single unit; for a 240V well pump, confirm with EcoFlow’s spec sheet and your electrician what setup is needed. Home-circuit connections require a licensed electrician.
What the example day means for battery sizing
| Goal (using the 8.6 kWh estimate) | Usable kWh needed | Rated capacity at about 87% usable |
|---|---|---|
| Overnight (about 12 hours) | about 4.3 | about 5 kWh |
| One full day | about 8.6 | about 10 kWh |
| Three days, no recharging | about 25.8 | about 30 kWh |
A single 3.6 kWh power station covers the example day for around 8 to 9 hours, or nearly a full day if you drop the furnace and well pump (a summer outage), where the example total falls to about 3.6 kWh. Covering multi-day winter outages on battery alone means expansion batteries, or recharging from solar or a generator. For solar recharging math, see how many solar panels it takes to recharge a home battery; winter solar output is much lower than summer. For the trade-offs between portable units and installed systems, see our power station vs home battery comparison.
Turning kWh Into Generator Fuel
A generator does not store energy; it converts fuel as you go. As a very rough rule of thumb, portable gasoline generators produce somewhere around 3 to 6 kWh of electricity per gallon, with the lower end at light loads, where open-frame generators running at fixed speed waste the most fuel. Inverter generators throttle down and do better at light loads. A 20 lb propane cylinder holds about 4.7 gallons and may deliver very roughly 15 to 25 kWh of electricity depending on the generator and load. Check your generator manual’s fuel consumption table for real figures.
Applied to the 8.6 kWh example, a mid-size generator might use around 1.5 to 3 gallons of gasoline per day if it runs only as needed, more if it idles at light load around the clock. A common strategy is a hybrid: run the generator a few hours a day to cover heavy loads and recharge a power station, which then runs the fridge, internet and furnace quietly overnight. Generators run outdoors only, at least 20 feet from the house with exhaust pointed away, with CO alarms inside, and any connection to home circuits must go through a transfer switch or interlock installed by a licensed electrician. Never backfeed through an outlet. Our best backup power for a 3-day outage guide compares these setups.
How to Choose a Backup Size
1. Find your baseline and measure essentials
Start from your winter bill and smart-meter overnight data, then measure plug-in loads with a plug-in meter and hardwired circuits with a panel monitor (installed by a licensed electrician). Build a table like the example above.
2. Check the largest starting surge
Make sure the inverter or generator output covers the biggest motor start plus everything else running.
3. Pick a duration and convert to capacity
Multiply daily essentials by the days you want to cover, then divide by about 0.85 to 0.90 for battery losses. Or estimate generator fuel from the manual’s consumption table.
4. Plan recharging and connection
Decide how a battery gets recharged during a long outage, and book a licensed electrician for the transfer switch, interlock or manufacturer’s home panel before storm season.
FAQ
How many kWh does a house use per day?
The US average is roughly 28 to 30 kWh per day (about 10,400 to 10,800 kWh per year, per recent EIA residential figures), but it varies widely with climate, home size, and electric versus gas heating.
How many kWh do essentials use during an outage?
For a gas-heated home, essentials often total roughly 5 to 12 kWh per day. Homes with electric heat or a large well pump need more. Measure your own loads to be sure.
Can a 3,600 Wh power station run a house?
Not a whole house for long. With roughly 3.0 to 3.2 kWh usable, it can run a fridge, internet, lights and a gas furnace blower for many hours, or longer on expansion batteries.
Why is usable battery capacity less than rated?
Inverter conversion losses and the unit’s own consumption mean roughly 85 to 90 percent of rated capacity is available as AC power, and cold temperatures reduce it further.
Bottom Line
A typical US home uses around 28 to 30 kWh a day, but outage essentials in a gas-heated home are more like 5 to 12 kWh. Find your real numbers from your bill, smart-meter data, a Kill A Watt for plug-in loads and a panel monitor like the Emporia Vue 3 or Refoss EM16P for circuits. Then size battery capacity at about 85 to 90 percent usable, or plan generator fuel from the manual, and leave the home connection to a licensed electrician.
If a generator fits your plan better, compare the best dual-fuel generators.
General information only, not professional advice. Details can change or contain errors, so check with the manufacturer or an official source before you rely on them. Use of this site is subject to our Disclaimer and Terms of Service.