Generator size is not determined by square footage alone. A compact rural home with electric heat, a deep-well pump and a sump pump can require more backup capacity than a larger city home with gas heat and municipal water. In New Brunswick, the right design begins with the equipment that must keep operating during ice storms, freezing rain, heavy snow, high winds and tree damage along rural distribution lines.
Greenfoot currently offers 18 kW, 22 kW and 26 kW standby packages, but those numbers only become meaningful after the load plan is defined. See the complete Canadian generator sizing and storm-prep guide for the national framework.
Direct answer: Add the running and startup requirements of the loads that may operate together, then apply load management and fuel-specific generator output. Do not size from a simple online appliance total without checking motor-starting demand, electric backup heat and the home's actual panel configuration.
Step 1: choose essential, important and optional loads
For many New Brunswick homes, essential loads include well pumps, sump pumps, septic or lift pumps, heating equipment, refrigeration and communications. Important comfort loads may include a microwave, selected kitchen circuits, a garage-door opener, television or one air-conditioning zone. Optional high-demand loads often include electric ranges, dryers, water heaters, hot tubs and EV chargers.
The point is not to recreate normal life without limits. It is to protect the home and keep the household safe while controlling generator size and fuel use.
Step 2: account for motor-starting demand
Well pumps, sump pumps, refrigerators, freezers, furnaces and heat pumps use motors or compressors. Their startup demand may be several times higher than the power used after they are running. If two large motors start together, a generator that looked adequate on a running-watt spreadsheet may overload.
A professional assessment should review equipment nameplates, manufacturer data and realistic operating combinations. It should also identify whether soft-start equipment or load-management controls are appropriate.
Step 3: understand heating loads
Heating can be the biggest source of sizing errors.
- A natural-gas, propane or oil furnace still needs electricity for controls, ignition and the blower.
- A boiler may require pumps, controls and zone valves.
- A ductless mini-split or central heat pump needs compressor and fan power.
- Electric auxiliary heat can be extremely demanding and may need to be locked out or managed during generator operation.
- Electric baseboards can consume most or all of a residential standby generator's capacity if too many zones operate together.
The backup plan may power the main heating zone while limiting electric resistance heat. Homeowners with heat pumps should coordinate generator sizing with the HVAC design rather than treating "home heating" as one generic number.
Step 4: size for water and flood protection
Rural and coastal homes may depend on a well pump, water-treatment equipment, septic pump or lift station. Basements may require one or more sump pumps. These systems are often the reason a homeowner needs backup power in the first place, so they must be treated as priority loads.
Confirm pump horsepower, voltage and startup characteristics. Also decide what happens if the primary sump pump fails mechanically; a generator powers the pump, but it does not replace a secondary pump or high-water alarm.
Step 5: choose essential-circuit or broad whole-home coverage
An essential-circuit design supplies a selected panel or group of circuits. It can be cost-effective and easy to understand, but future changes require planning.
A service-rated whole-home design can make most circuits available while load-management controls prevent several large appliances from operating together. "Whole home" therefore means broad access, not necessarily unlimited simultaneous use.
How 18 kW, 22 kW and 26 kW systems are commonly positioned
These are planning categories, not promises:
Generator output can vary by fuel. Ask for the rated output on the fuel that will actually be used at the property.
Five sizing questions to ask an installer
- Which exact circuits will operate during an outage?
- Which loads are automatically managed or locked out?
- What is the largest motor-starting event in the home?
- How is electric auxiliary heat handled?
- What future loads should be included now?
Get a real load assessment
Greenfoot provides generator assessments across Moncton, Fredericton, Saint John and Tracadie-Sheila. The assessment reviews the panel, fuel source, equipment loads, placement and permit path before recommending a system.
Read the main backup-power sizing guide and explore Greenfoot's standby-generator installation options before choosing capacity from an online chart.