Emergency Power Supply: What to Back Up and How to Size It

An emergency power supply is only one part of preparedness. Start with medical needs, communications, safe lighting, refrigeration and property protection. Size battery energy for the time between reliable charging opportunities, then maintain a non-electric emergency kit for at least 72 hours as recommended by Public Safety Canada.

This guide gives a practical way to turn the main keyword power supply emergency into a real load plan. The examples are planning estimates rather than product guarantees. Actual results change with device cycling, startup demand, temperature, battery condition, conversion losses, cable length, solar weather and the way equipment is used.

Quick Answer

The safest buying sequence is to confirm the load, calculate required energy, check continuous and startup power, and only then select a battery and charging method. A high inverter rating cannot compensate for insufficient watt-hours, and a large battery cannot run an appliance whose voltage or startup demand is incompatible.

Understand the Ratings Before Buying

List critical devices by priority, watts, hours, startup demand and acceptable downtime. Add required cables, spare batteries, lighting, radio, contact information and recharge methods.

Watts describe power at a moment. Watt-hours describe energy used over time. Amps describe current, while voltage is the electrical pressure that drives it. For a simple DC estimate, watts equal volts multiplied by amps. AC appliances may also involve power factor, so the label or direct measurement is preferable to an assumed calculation.

For motors, compressors and pumps, look for startup or locked-rotor demand as well as ordinary running power. For batteries, compare the published capacity, output waveform, port-specific limits, operating temperature and cycle-life definition. Do not assume that every socket can provide its printed maximum simultaneously; shared system limits usually apply.

Typical Power Ranges

The ranges below are orientation values, not substitutes for the actual equipment label. Two devices with the same general description can have very different efficiency, control logic and startup behaviour.

Device or System	Planning Range	Important Qualification
Communications kit	100-300Wh/day	Phones, radio and lights
Medical/office essentials	300-1,000Wh/day	Device-specific verification required
Refrigeration bundle	1-2kWh/day	Measure actual appliance energy
Home protection loads	Variable/high surge	Pump and furnace planning

Calculate Energy and Runtime

Use three simple formulas:

Energy used (Wh) = average watts x operating hours.
Required rated battery (Wh) = load energy / assumed usable-system factor.
Estimated runtime (hours) = rated Wh x usable-system factor / average load watts.

The examples use an 85% usable-system factor to represent inverter and conversion losses plus a small operating margin. This is not a guaranteed efficiency figure. Heavy loads, cold temperatures, aging, power factor and battery protection limits may reduce the result.

Example Load	Calculated Energy	Planning Battery at 85%
Router 15W x 24h + phones 60Wh	420Wh/day	About 494Wh
Lights 40W x 6h + radio 30Wh	270Wh/day	About 318Wh
Fridge 1kWh + communications 420Wh	1,420Wh/day	About 1,671Wh
1.4kWh/day x 3 days	4,200Wh	About 4,941Wh

Measure cycling equipment over a representative period instead of multiplying its running watts by 24 hours. Refrigerators, pumps, air conditioners and many chargers switch on and off. Conversely, do not ignore short high-power events: they may determine the inverter size even when their total energy is small.

Step-by-Step Sizing Method

List essential loads. Separate safety, medical, communications and property-protection needs from optional comfort devices.
Record real ratings. Use nameplates, manuals, EnerGuide data or a suitable meter. Include every adapter and accessory.
Calculate daily watt-hours. For cycling devices, use measured energy or a realistic duty cycle.
Check simultaneous watts. Add only the devices that may operate at the same time, then include practical headroom.
Check startup and voltage. Confirm the largest realistic motor event and every 120V, 240V or regulated DC requirement.
Plan recharge. Decide how much energy must be restored by AC, vehicle or solar input before the next use period.
Add uncertainty. Weather, cold, device aging, extra users and delayed travel all justify reserve capacity.

Planning by Scenario

Scenario	Practical Starting Strategy	Constraint to Verify
Apartment	Portable station and individual cords	Elevators and building services may fail
Family home	Prioritized battery system	Add food, water and heat plan
Medical dependency	Redundant power and care location	Coordinate with healthcare provider
Rural property	Battery plus safe generator recharge	Fuel and access can be disrupted

A planning table is useful because it exposes trade-offs. The lightest system is easier to move but offers less resilience. A larger system extends runtime but costs more, weighs more and may need a stronger solar array or AC circuit to recharge within the available window.

OUPES Product Options

OUPES models should be recommended only when their verified output, capacity, ports and charging limits fit the load plan. The following comparison uses specifications published on the Canadian product pages. Availability and bundle pricing can change, so confirm the live page before publication.

OUPES Model	Capacity	Rated AC Output	Published Solar Input	Best-Fit Role and Limitation
OUPES Exodus 1200	992Wh	1,200W	240W max	Light camping, communications, CPAP planning and managed essentials. Best starting point when the power supply emergency plan is efficient and tightly managed.
OUPES Mega 1	1,024Wh	2,000W	1,200W max	Higher-watt appliances, short home backup and mixed mobile loads. Useful when the plan includes brief high-watt loads or requires more output headroom.
OUPES Exodus 2400	2,232Wh	2,400W	800W max	Longer runtime and demanding 120V loads; currently shown as sold out on the CA site. Adds substantially more stored energy for longer sessions; confirm current availability.
OUPES Mega 3	3,072Wh	3,600W	2,100W max	Home backup, RV use and larger simultaneous load plans. Best suited to broader home, RV or multi-load plans that justify the extra capacity and weight.

The OUPES Exodus 1200 is the lighter 992Wh option, while the OUPES Mega 1 combines 1,024Wh with 2,000W output. The OUPES Exodus 2400 provides 2,232Wh and 2,400W but is currently marked sold out on the Canadian site. The OUPES Mega 3 offers 3,072Wh, 3,600W output and expansion for larger plans. Choose from the measured requirement rather than assuming the largest model is automatically best.

You can also review the Canadian portable power station collection. Use the commercial category link once, then let the product specifications and the user's scenario drive the recommendation.

Solar and Recharging

Solar charging should be planned from daily energy. A rough estimate is panel watts x equivalent full-sun hours x system factor. A 240W panel with four equivalent full-sun hours and a 70% planning factor would provide about 672Wh in that example day. Clouds, shade, snow, orientation, temperature, cable loss and the station's input limit can all reduce the result.

The OUPES 100W and 240W panels list monocrystalline cells, MC4 connectors and at least 23% cell efficiency. The 100W panel lists 24.4V open-circuit voltage and 4.88A operating current; the 240W model lists 24.6V open-circuit voltage and 11.7A operating current. Before combining panels, calculate total voltage and current and compare them with the selected station's entire MPPT window.

For a combined battery-and-panel package, review the Canadian solar generator collection. Nameplate solar wattage is not guaranteed field output, so critical plans need reserve energy or another compatible charging route.

Safety and Canadian Conditions

Do not use candles unattended, run fuel equipment indoors or improvise home wiring connections. Protect batteries and cords from water and keep carbon-monoxide alarms working.

Canadian conditions introduce real planning limits: winter days are short, snow and shade affect panels, cold can limit charging, and summer heat can increase cooling or refrigeration demand. Use equipment only within its published operating and storage temperatures. Keep vents open, inspect cords and connectors, and stop using anything that is damaged, unusually hot or wet.

Fuel generators are a different category from battery systems. They create carbon monoxide and must remain outdoors at the distance and orientation required by current safety guidance. A battery unit avoids combustion exhaust at the point of use, but it still requires dry conditions, ventilation and safe wiring.

Common Mistakes to Avoid

Choosing from one headline watt number without checking watt-hours, surge, voltage and ports.
Using advertised appliance output instead of electrical input.
Assuming rated battery energy is fully available as AC energy.
Using the best solar day as the normal or worst-case charging day.
Ignoring simultaneous loads, compressor startup or pump cycling.
Using unverified adapters, reversed DC polarity or undersized extension cords.
Connecting backup power to a building through an improvised backfeed cord.
Publishing a runtime estimate without stating its efficiency, duty-cycle and weather assumptions.

Final Verdict

For a reliable decision, measure first and buy second. Match inverter power to the worst realistic simultaneous and startup load; match battery watt-hours to the target runtime; and match solar or AC input to the energy that must be restored. Leave reserve for the conditions that a simple calculator cannot predict.

Frequently Asked Questions

How much emergency battery capacity is enough?

Total critical Wh for the target period, apply losses and add reserve; do not rely on a universal number.

What should be powered first?

Medical equipment, communications, safety lighting, refrigeration and property-protection systems.

Is 72 hours of battery required?

Public Safety Canada recommends household self-sufficiency for at least 72 hours, but the plan can combine battery, supplies and safe recharge.

Can I recharge from a car?

Only with supported equipment and without risking the starter battery or operating the vehicle in an unsafe area.

Can solar be my only emergency source?

It can help, but prolonged storms and winter conditions justify reserve energy or another safe source.

How often should supplies be checked?

Review the plan at least annually and test batteries, cables and critical devices periodically.

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