Good standby generator installation begins with a list of the household systems that must keep working during an outage. That list determines the generator’s capacity, which circuits it serves, the transfer equipment it needs and the fuel arrangement that makes sense. A larger generator can power more equipment, but may add cost and installation complexity without solving a real household need. Start by identifying essential loads and which ones may run at the same time, then have a qualified installer check starting demand, electrical compatibility, fuel supply and the proposed site.
Make a circuit-by-circuit list before discussing generator capacity. Separate essential services from equipment that would be convenient but can remain off. The right list will vary by household: one home may need a water pump, refrigeration and heating controls, while another may prioritise medical equipment, a sump pump or communications.
Include the systems behind the visible appliance. A heat pump, for example, may rely on controls and circulation equipment as well as its main unit. If a medical device is involved, confirm its power requirements with the equipment supplier or care provider. A generator may not replace a battery or uninterruptible power supply where uninterrupted operation is required during the changeover.
Also decide how the household will use power when the generator is running. If heating, cooking and water pumping do not need to operate at once, a smaller system with a clear load-management plan may be suitable. If occupants need to use those loads freely, the generator and electrical arrangement must accommodate a higher combined demand.
Generator sizing is based on the electrical demand the system must support, not simply the number of rooms or appliances in a house. Two figures matter: the power equipment uses while running and the higher demand some motors or compressors can draw as they start. Refrigerators, pumps and heat pumps can be particularly important to check for starting demand.
Gather appliance nameplates, manuals or manufacturer data where available. Record each load’s running demand, starting requirement if specified, and whether it is essential. An installer can use this information alongside the home’s electrical supply and circuit layout to calculate a suitable capacity. Avoid relying on a rough appliance count or adding only the normal running figures; either approach can miss a startup peak or assume that incompatible loads will never overlap.
| Coverage approach | What it can supply | Main advantage | Trade-off to consider |
|---|---|---|---|
| Essential-circuit backup | A selected group of high-priority circuits, such as refrigeration, lighting and communications | Limits the loads the generator must support | Some appliances and rooms remain without backup power |
| Managed partial-home backup | Essential circuits plus selected larger loads, with controls or operating rules to limit simultaneous demand | Balances broader coverage with controlled demand | Loads may need to be sequenced or automatically managed |
| Broad whole-home backup | Most or all household circuits, subject to generator capacity and any load controls | Allows more normal household use during an outage | Can require a larger system and may still need load management |
The table is a planning guide, not a capacity calculation. “Whole-home” does not automatically mean every high-demand appliance can run together. Ask the installer to document which loads can operate simultaneously and what happens if demand exceeds the generator’s available output.
Check the electrical supply as well as the total load. Homes can have different supply arrangements, including single-phase or three-phase service, and the generator and transfer equipment must suit the circuits being backed up. The installer should also confirm the generator’s rated output for the proposed fuel and operating conditions, rather than sizing from a headline figure alone.
A standby generator needs equipment that changes the home’s supply from the network to the generator safely. An automatic transfer switch can detect a supply interruption and, when configured for automatic operation, transfer the selected loads to the generator. A manual transfer arrangement requires the homeowner to follow the specified switching procedure instead.
The transfer arrangement also prevents the generator from energising network wiring while it is connected to the home. This protection is essential. Never connect a generator to a household socket or improvise a connection through an extension lead; that can create a dangerous backfeed and is not a substitute for correctly installed transfer equipment.
For essential-circuit backup, the installer may use a separate backed-up panel. A broader installation may use a transfer switch serving more of the home, with load-management equipment to control high-demand appliances. Ask for a circuit schedule that shows exactly what is backed up, what is excluded and whether any loads must be disabled or sequenced during generator operation.
Fuel choice affects installation design, storage, maintenance and the possibility of operating for an extended outage. The appropriate option depends on what is available at the property and whether the supply can support the generator’s demand. Do not assume that a fuel connection or stored supply will be adequate simply because it already serves the house.
Runtime depends on the generator, its load and the available fuel supply; a general estimate cannot guarantee how long a particular installation will run. Ask the installer to explain the manufacturer’s runtime information for the loads you expect to use, how fuel is replenished and what maintenance is required after periods of inactivity. In a rural or difficult-to-access location, delivery access and household storage may be as important as the generator’s rated capacity.
A suitable site needs more than enough room for the generator itself. The unit requires a stable base, access for servicing, adequate airflow and an exhaust arrangement that directs emissions away from people and openings. The exact placement and clearances depend on the equipment instructions and site conditions, so do not use a generic distance as a substitute for the manufacturer’s requirements.
Carbon monoxide is a serious risk from engine exhaust. A standby generator must be installed outdoors as specified by its manufacturer, not in a house, garage or other enclosed space. The installer should assess nearby doors, windows and ventilation openings, as well as boundaries, neighbouring properties, drainage, weather exposure and noise considerations.
In New Zealand, have fixed electrical work designed and connected by an appropriately licensed electrical worker. If the project includes gas work, involve a licensed gasfitter. Ask the installer to confirm any council, consent, fuel-storage or local noise requirements that apply to the property; these can depend on the equipment, location and proposed work. Keep the manufacturer’s installation instructions and any relevant approval information with the household records.
The generator is only one part of the project. A quote may also need to cover transfer equipment, a backed-up circuit panel, wiring, load controls, fuel connections, a base, trenching or other site work, commissioning and any required approvals. Existing switchboards, distance between the generator and connection point, access constraints and changes to the fuel supply can affect the work involved.
Request an itemised quote that states the generator model and rated output, the circuits or loads included, the transfer method, fuel arrangement and what site work is covered. Ask whether commissioning, homeowner instruction and the initial maintenance information are included. When comparing proposals, make sure each contractor has priced the same coverage and operating assumptions; a lower quote may provide backup for fewer loads or omit work another proposal includes.
Before accepting a design, ask the installer to show how the system handles the largest starting load, which appliances cannot run together, and what happens if a managed load exceeds its limit. Also confirm who is responsible for any council or consent checks and whether the quoted fuel arrangement requires changes to existing services.
Commissioning is where the installer checks that the equipment and transfer arrangement work as designed. The scope should include the generator’s operation, the changeover between normal and backup supply, the selected circuits and any load-management controls. Ask for a practical explanation of the indicators, alarms and shutdown instructions, not just a handover of the equipment manual.
Before the installer leaves, confirm how the system’s automatic test or exercise function is set up, if fitted, and what maintenance schedule applies. Make sure household members know what to do if an outage occurs, which loads to limit and whom to contact if the generator reports a fault. Keep the circuit schedule, manuals, service details and fuel-system information in an accessible place.
It can, if the generator, transfer equipment and electrical design support the household’s demand. Some installations use load management so that high-demand appliances do not run together. Ask for a written list of included circuits and any restrictions before choosing a whole-home arrangement.
List the essential circuits and appliances, then gather their running and starting demand where available. A qualified installer should check the combined loads, electrical supply and proposed transfer arrangement to recommend capacity. The result should reflect how the household will actually use power during an outage.
It can if the installation includes a compatible automatic transfer arrangement and is configured for automatic operation. Other transfer setups require manual action. Confirm the expected sequence with the installer and make sure household members know how to respond if the system does not operate as expected.
Not necessarily without additional compatible equipment and controls. Many grid-connected solar systems stop operating when the network supply fails, and a generator can complicate the design. Have the solar and generator manufacturers’ requirements checked by an installer experienced with both systems before connecting them.
Runtime depends on the generator’s fuel source, available supply and the loads being served. Ask for an estimate based on the specific model and expected demand, and confirm how replenishment and maintenance work for the chosen fuel arrangement.
A well-planned standby generator installation starts with the circuits that matter most, then matches capacity, transfer equipment, fuel and site conditions to those needs. Before committing, ask for a documented load plan and a clear quote covering the complete installation, commissioning and operating limitations.
