When the grid fails and you switch to backup power, everything changes: your electricity is no longer effectively unlimited. A battery or generator has a fixed budget of watt-hours, and every device you run spends it. The most powerful thing you can do to make backup power last is not to buy a bigger battery — it is to need less power in the first place.
This guide is the outage-time application of everyday efficiency. It assumes you have a backup source and want it to last as long as possible. If you are still deciding what to buy or how big it should be, start with the backup power planning hub and the load worksheet. Here, the power is already out and the clock is running.
The one rule: reduce before you replace
The backup power hub opens with it and it is worth repeating: reduce the load before increasing the power source. A 100-watt load saved for 10 hours is a full kilowatt-hour you did not have to store. Shedding load is instant, free, and reversible — the opposite of buying more capacity.
Sort your loads under pressure
Before an outage, and again the moment one starts, sort every device into three tiers. This mirrors the load categories in the load worksheet but here the goal is triage, not sizing.
Critical — never shed
- Prescribed medical equipment (set by your care plan, not by this guide)
- Well or sump pumps where loss threatens health or the building
- One communication device kept charged for emergencies
- Carbon monoxide and smoke alarms
Essential — run in planned cycles
- Refrigerator and freezer (run intermittently if the appliance and food-safety plan allow)
- Limited task lighting
- Phone and radio charging
- Minimal heating or cooling within a safe-room strategy
Deferrable — shed immediately
- Entertainment beyond one small device, most electronics
- Electric cooking, kettles, toasters, and other high-wattage heat
- Laundry, dishwashers, and convenience appliances
- Anything already on your everyday standby-power cut list
High-wattage heat is the budget killer
The fastest way to drain a backup system is to make heat with electricity. A 1,500-watt space heater or kettle can consume 1.5 kWh in a single hour of continuous running — often more than a small power station holds in total. Electric resistance heat, hair dryers, toasters, and stovetops are the biggest single line items you can cut.
During an outage, meet heat needs with insulation, layers, bedding, safe non-electric cooking, and a warm safe room rather than electric heat. This is where your everyday weatherization pays off directly: a well-sealed home holds temperature far longer, so you spend fewer watt-hours fighting the cold or the heat. The weatherization priorities guide explains that thermal coasting.
Run the refrigerator, do not babysit it
The refrigerator is usually the load people most want to keep, and it is manageable because it cycles. Rather than powering it continuously:
- Keep the door closed as much as possible. A full fridge holds cold longer.
- Run the appliance for planned intervals to bring temperature back down, then let it coast.
- Judge food by temperature, not by whether the fridge “was on.” Follow the power outage food safety guide and FoodSafety.gov thresholds. (Source: FoodSafety.gov, Food Safety During a Power Outage.)
The power a refrigerator during an outage guide covers this cycling in detail, including how to size the load honestly.
Measure so you shed the right things
Guessing which devices are expensive wastes effort. Before an outage season, use a plug-in watt meter to record the running and standby watts of the devices you might keep on backup. DOE guidance notes that nameplate ratings can overstate normal use, so measured values give you a realistic load list. (Source: U.S. Department of Energy, Estimating Appliance and Home Electronic Energy Use.) A short worksheet of measured watts is worth more in an outage than any spec sheet.
Load-shedding sequence when the power drops
- Turn off everything, then add back only what you need. Starting from zero is easier than trimming from a full house.
- Kill all standby and deferrable loads first. Strips off, chargers out, entertainment down to one device.
- Confirm critical loads are supported and, for medical equipment, that you are following the manufacturer and care-plan instructions.
- Schedule essential loads in cycles rather than running them simultaneously — refrigerator, then charging, then brief lighting.
- Avoid electric heat entirely unless a professionally designed plan requires it.
- Recheck the budget. Estimate remaining watt-hours against expected outage length and the next recharge opportunity.
Match the plan to your power source
- A small power station rewards ruthless shedding: keep it for phones, a radio, task light, and short refrigerator cycles, and do not attempt electric heat.
- A generator gives more headroom but keeps every fuel, noise, and carbon-monoxide constraint — read generator carbon monoxide safety before running one, and never connect it to household wiring without a qualified electrician and listed transfer equipment.
- Solar recharge varies with weather; shedding load is what makes an uncertain recharge enough. See portable solar panels for outages.
Prepare the plan before you need it
Load-shedding works best when it is rehearsed, not improvised in the dark. Do three things before outage season:
- Write a one-page priority list. List your critical, essential, and deferrable loads with their measured watts, and post it where the backup gear is stored. Deciding what to cut is far harder by flashlight during a storm.
- Pre-stage the tools. Keep working flashlights or lanterns, charged battery banks, the backup unit itself charged or fueled within safe limits, and a manual can opener and non-electric cooking option ready.
- Run a dry run. Once, on a calm evening, switch to backup and live on it for an hour. You will discover which loads you forgot, whether your battery lasts as expected, and whether everyone can find what they need. A rehearsal turns a stressful event into a routine one.
Adjust the plan to the season
The loads worth protecting shift with the weather, and so does the danger of getting it wrong.
- Summer outage. The threat is heat. Prioritize fans, keeping the refrigerator cold, and a cool safe room. Do not waste watt-hours on anything that adds heat, and have a cooling-center fallback if the home climbs to unsafe temperatures.
- Winter outage. The threat is cold and carbon monoxide. Prioritize communication, limited safe lighting, and protecting pipes, while meeting warmth with layers, bedding, and a sealed safe room rather than electric heat. Never run a generator or fuel-burning heater in living space.
- Storm or hurricane outage. These can last for days, so plan for the longest realistic gap between recharges and lean hardest on load reduction from the first hour.
Keep a non-electric fallback
Load-shedding buys time; it does not create energy. Always keep a fallback that needs no electricity at all: warm clothing and bedding, a safe manual cooking method, stored water, and a plan to relocate to a warming or cooling center if the outage outlasts your reserves. Efficiency stretches your backup; it does not replace an evacuation option.
Return to the home energy efficiency hub to build these habits before an outage, so shedding load under pressure is routine rather than improvised.
Sources reviewed
- U.S. Department of Energy, Energy Saver: Estimating Appliance and Home Electronic Energy Use; standby-power guidance
- FoodSafety.gov: Food Safety During a Power Outage
- U.S. Energy Information Administration: Use of energy in homes
Sources reviewed July 14, 2026.