Power Rationing After Day Three

A blackout becomes a supply problem when every remaining watt must accomplish something important.

During the first day of a power failure, most households try to preserve normal life. Lights remain on. Phones are charged whenever convenient. The refrigerator runs normally. Someone makes coffee with an electric appliance because the backup system appears to have plenty of capacity.

By the third day, the arithmetic has usually changed.

Solar production may be below expectations. Generator fuel is disappearing faster than planned. The battery display drops sooner each night. Nobody knows whether the grid will return tomorrow or next week.

This is when backup power must stop being treated as a substitute for the electrical grid. It becomes a rationed resource—more like stored food, potable water or medical supplies. Every load must justify the energy it consumes.

Rated Capacity Is Not Available Energy

A portable power station labelled 2,048 watt-hours does not necessarily provide 2,048 watt-hours to household appliances.

Some capacity should remain unused to protect the battery and preserve an emergency reserve. Converting stored DC electricity into household AC power also consumes energy. Cold temperatures, battery age, wiring losses and inverter standby consumption reduce what reaches the appliance.

Suppose a 2,048-watt-hour power station has a planned usable limit of 85 per cent and delivers AC power at an assumed overall efficiency of 90 per cent:

2,048 × 0.85 × 0.90 = approximately 1,567 usable watt-hours

That is the number that belongs in the household power plan—not the larger number printed on the case.

The actual figures should come from the equipment manual and, whenever possible, from direct testing. Inverter efficiency and standby consumption vary between systems. Manufacturers publish efficiency and idle-consumption specifications because not every stored watt reaches the load. For an example of the figures provided with charging equipment, see Victron Energy’s technical literature.

Stop Asking What You Can Run

The wrong question is: “What appliances can this power station run?”

A large inverter may run a microwave, toaster, coffee maker or power tool. That does not mean those loads deserve a place in a prolonged outage.

The better question is: What must this system accomplish every day, and how much energy can be spent doing it?

Divide electrical loads into three groups.

Tier One: Life and System Protection

These are loads whose loss can quickly threaten life, health or the property systems keeping the household habitable.

• Essential medical equipment
• A sump or drainage pump
• Controls and circulation pumps for an operable heating system
• A well or transfer pump needed to obtain water
• Freeze-protection equipment for vulnerable plumbing
• Essential security or fire-detection equipment

Medical equipment must be calculated from its documented consumption and required operating time. It should never be assigned an optimistic estimate or forced into an improvised operating schedule that contradicts its instructions.

Tier Two: Continuing Household Capability

These loads preserve food, communications, sanitation and the ability to work.

• A refrigerator or freezer
• Amateur-radio and receiving equipment
• Charging for handheld radios and telephones
• Limited task lighting
• A laptop or tablet used for records, maps or communications
• Occasional pumping or water-treatment equipment
• Essential tool-battery charging

These loads normally receive scheduled operating windows rather than unrestricted access to power.

Tier Three: Convenience

Televisions, decorative lighting, entertainment systems, countertop cooking appliances and casual device charging belong here.

A Tier Three appliance can be temporarily promoted when it performs a worthwhile task. A power tool used to repair a damaged shelter is no longer a convenience. An electric kettle used merely because it is familiar still consumes a large burst of energy that could have powered communications and lighting for hours.

The category depends upon the task—not the product.

Build the Daily Watt-Hour Budget

Watts describe how much power a device demands at a given moment. Watt-hours describe how much energy it consumes over time.

A 20-watt lighting system used for five hours consumes 100 watt-hours. A 600-watt pump running for twelve minutes—one-fifth of an hour—consumes approximately 120 watt-hours.

Cycling appliances are more difficult. A refrigerator does not run continuously, and its consumption changes with room temperature, door openings, thermostat setting and the condition of its seals and coils. The useful figure is its measured consumption over a representative 24-hour period.

A plug-in electricity meter can provide that figure for most cord-connected AC appliances. Built-in battery monitors and power-station displays can help measure DC loads and complete circuits.

Adding a 20 per cent operating margin raises the requirement to approximately 1,488 watt-hours.

Our example 2,048-watt-hour power station offered about 1,567 usable watt-hours. It does not provide several comfortable days of electricity. Under this load plan, it provides approximately one day before it must be recharged.

That is the kind of discovery to make during a drill—not on the third night of an actual outage.

Create Power Windows

Unrestricted electricity encourages invisible waste. A power window concentrates several necessary tasks into one period.

Morning Operations Window

• Assess battery state and overnight consumption.
• Receive scheduled radio traffic.
• Operate the water pump.
• Charge handheld radios and telephones.
• Check refrigeration temperatures.
• Update the written power ledger.

Midday Production Window

This is the preferred period for discretionary loads when solar production is available.

• Charge the main battery bank.
• Operate pumps or tools.
• Complete laptop work.
• Charge removable batteries.
• Run other loads directly from incoming solar power where the system permits.

Using energy while it is being produced can reduce the amount that must pass into and then back out of the battery. Essential charging still takes priority over optional work.

Evening Operations Window

• Receive communications updates.
• Provide task lighting for cooking, medical care and household organization.
• Complete the final device-charging period.
• Prepare equipment for overnight operation.

Overnight Conservation Period

Only loads approved for continuous operation remain energized. The main inverter should not stay on merely to provide idle wall outlets if the system can safely power essential loads another way.

The exact schedule will differ between households. The important point is that everyone knows when power will be available and what work must be completed during each window.

Make Refrigeration Earn Its Share

Refrigeration often becomes the largest continuing household load. It may still be worth every watt because it protects meat, medication and other difficult-to-replace supplies.

Begin by deciding what truly requires refrigeration. Remove beverages and other items that do not justify repeated door openings. Consolidate frozen food into the most efficient appliance while leaving adequate room for designed air circulation. Use appliance thermometers so decisions are based on temperature rather than guesswork.

Keep an inventory on the outside. Decide what is needed before opening the door, retrieve everything at once and close it promptly.

Do not create an arbitrary on-and-off schedule without monitoring food temperatures. The objective is to reduce unnecessary compressor operation and door openings—not repeatedly allow food to warm and hope it remains safe.

As supplies are consumed, the value of refrigeration may change. A nearly empty freezer consuming a large share of the daily budget may eventually be less important than pumping water, maintaining communications or protecting the heating system.

That decision should be made deliberately.

Solar Production Is Income, Not Capacity

Battery capacity is stored wealth. Solar production is daily income.

The two should not be confused.

A system with a large battery but poor daily production eventually becomes empty. A large solar array with insufficient storage may produce more electricity than the household can use at noon while leaving it powerless overnight.

Never write the solar panel’s advertised output into the rationing plan as guaranteed production. Trees, cloud, snow, low sun angles, short Canadian winter days, panel orientation and charge-controller limits can all reduce the harvest.

Record actual daily production. After several days, the household can answer the question that matters:

Is the system producing more energy each day than the essential loads consume?

If the answer is no, conservation must begin immediately. Waiting until the battery reaches its low-voltage cutoff turns a controlled reduction into an abrupt failure.

Use Generator Time to Accomplish Several Jobs

A generator is most valuable when its operating period performs several useful tasks.

A planned generator window can recharge the main battery bank, cool refrigeration equipment, pump water and charge portable batteries at the same time—provided the combined load remains within the generator’s continuous rating and individual starting surges are managed.

Record fuel use by operating session. “Half a tank” is not a usable planning figure. The household needs to know approximately how many litres are consumed during a normal recharge cycle and how many cycles remain.

Fuel should also maintain a protected reserve for high-priority events: extended bad weather, a medical requirement, frozen plumbing, floodwater or failure of another charging source.

A generator that runs whenever someone wants an appliance will consume its fuel according to convenience. A generator operated according to a written schedule converts a finite fuel supply into predictable days of capability.

Keep a Written Power Ledger

Digital displays show what is happening now. A paper ledger shows whether the household is winning or losing.

Record:

• Morning battery state
• Energy used during the previous day
• Solar energy collected
• Generator operating time
• Fuel consumed
• Unusual loads
• Estimated days of fuel remaining
• Conservation changes ordered for the next day

After three entries, trends become visible. If consumption exceeds production every day, the plan is unsustainable regardless of how reassuring the battery display looks that morning.

The ledger also prevents disputes. People can see why charging periods were shortened or why a convenience load was removed. The decision becomes a matter of arithmetic rather than preference.

Establish Reduction Triggers Before the Outage

Do not wait until the system is nearly depleted to decide what gets disconnected.

The exact battery percentages must reflect the equipment, chemistry and household needs. The value of the trigger system is that the difficult decisions have already been made.

Test the Plan for a Full Weekend

A tabletop calculation cannot reveal every load.

Disconnect the household from normal electrical habits for a weekend without interfering with any essential medical or safety system. Measure refrigeration, pumping, communications and lighting. Record every unexpected use of electricity.

The test will expose chargers that were forgotten, appliances with high starting surges, batteries that recharge too slowly and family members who did not understand the operating schedule.

More importantly, it will reveal whether the household can follow the plan.

Backup electricity is reassuring during the first few hours of an outage. Long-term resilience begins when that electricity is measured, prioritized and denied to anything that cannot justify its share.

If your household entered the red stage tonight, which load would you disconnect first—and has everyone else already agreed?

Related Reading

• Energy Production in Canada: build a complete emergency-power system
• Energy Production & Blackout Power Buying Guide
• Your Vehicle Is a Power Plant: understand another source of emergency electricity

Turn the Numbers Into a Household Rule

Print the load budget, write the operating windows beside it and post the reduction triggers where everyone can see them. When the outage begins, the household should not need another meeting to decide whether entertainment outranks refrigeration, water, heat or communications.