Backup generator installation should begin with a clear list of the household systems you need during an outage. A refrigerator, heating controls, water pump, medical equipment and a few lights may matter more than running every appliance at once. Once you identify those priorities, an installer can match generator capacity to the loads, check starting demands, and plan the transfer equipment, fuel supply and installation site. This approach helps prevent an undersized system that trips under load or a larger, more costly setup than your household needs. It also gives you a realistic basis for comparing quotes and planning how the generator will operate.
Start by considering what an outage would mean in your home. A household that relies on a pump for water has different priorities from one that mainly needs refrigeration, internet and lighting. Your list should reflect how you actually live, not simply which appliances are connected to the house.
Write down each essential device or system, then mark whether it must run continuously, can be used intermittently, or can be left off. Include the people who depend on the equipment and the length of outage you want to prepare for. If someone uses medical equipment, check the equipment’s power requirements and discuss a suitable continuity plan with their healthcare provider; a generator should not be treated as the only safeguard for critical care.
| Household load | Planning question | What to confirm |
|---|---|---|
| Refrigerator or freezer | Does it need continuous power, or can use be prioritised during an outage? | Operating demand and any brief starting demand shown by the manufacturer |
| Heating or cooling | Which parts of the system are needed, and in which conditions? | Whether the generator can support the equipment’s starting and running requirements |
| Water, drainage or other pumps | Would losing the pump interrupt an essential household service? | Motor starting demand and whether the pump can be scheduled or managed |
| Medical equipment | What level of continuity is required? | Equipment specifications and an appropriate backup plan with the care provider |
| Lighting, internet and charging | Which rooms and devices need power, and for how long? | The circuits serving them and whether other loads share those circuits |
Use appliance labels, manuals or manufacturer information as a starting point, but don’t assume that a household’s total connected load is the amount the generator must supply. The relevant figure depends on which loads will run together and whether some need extra power to start. An electrical professional can help check the figures and the circuits behind them.
Put each item in one of three groups:
This exercise makes sizing more practical. For example, a household might prioritise refrigeration, lights, communications and a pump, while treating cooking or high-demand heating equipment as flexible or excluded. The right combination depends on the home and its occupants; don’t assume that a load is low-demand just because it is used only occasionally.
Think through a realistic outage routine, too. If several people will use appliances at once, the generator may need to carry a higher combined load than a plan based on one device at a time. If you are comfortable staggering certain tasks, a smaller system or load-management setup may be suitable. Be honest about how much coordination the household will maintain during a stressful outage.
Generators are commonly described by their power output, but a single headline rating does not tell the whole story. Check the manufacturer’s stated continuous output as well as any higher short-duration or starting rating. A generator must support the ongoing load and cope with equipment that briefly draws more power when it starts.
Motors in pumps and some heating or cooling equipment can create a significant starting demand. If several such loads may start at the same time, the system needs to account for that possibility. An installer can assess whether loads should be sequenced or controlled so that the generator does not face their starting demands together.
Ask how the proposed capacity was calculated. The estimate should be based on the selected circuits, appliance requirements and intended use—not simply the home’s main supply rating or a guess based on floor area. Confirm that the generator’s output is compatible with the home’s electrical system and the transfer equipment being proposed.
Choosing a generator with too little capacity can mean tripping, limited use or the need to switch equipment off whenever another load starts. Choosing far more capacity than the plan requires can raise equipment and installation costs without adding useful backup for the loads you care about. If you want the option to run additional equipment later, identify those future loads before comparing generator sizes.
Generator type and transfer arrangement affect convenience, installation scope and cost. A portable unit may suit a household that accepts manual setup and limited backup circuits. A permanently installed standby generator can be more convenient for frequent or prolonged outages, but usually involves a more extensive installation. Neither option is automatically right for every home.
| Setup | How it is used | Main advantage | Key limitation to plan for |
|---|---|---|---|
| Portable generator with suitable transfer equipment | Positioned and started when needed, then connected through an approved inlet and transfer arrangement | Can provide a more limited backup setup without installing a permanent generator | Requires safe outdoor placement, setup, fuel management and user attention |
| Standby generator serving selected circuits | Installed in a fixed location and connected to designated backup circuits | Focuses capacity on the household’s chosen priorities | Loads outside those circuits will not receive backup power |
| Standby generator with broader coverage and load management | Installed to support a wider set of household loads, with controls to manage demand where needed | Can reduce the need to choose between as many circuits during an outage | Capacity, controls, fuel arrangements and installation requirements can increase project complexity |
A transfer switch or other approved transfer arrangement isolates the generator supply from the normal supply. This is essential to a safe, correctly designed connection. Never connect a generator to household wiring by plugging it into a wall outlet; this can create dangerous backfeed. Have the transfer equipment selected and installed by an appropriately qualified electrical professional.
With selected-circuit backup, the installer connects the chosen circuits to the transfer equipment. This can suit homeowners who have a short, clear list of priorities and are willing to leave other circuits off. Ask which outlets and fixed equipment are actually served by each circuit; a circuit label alone may not tell you every device connected to it.
Broader coverage may be useful if you want more flexibility, but it does not automatically mean every large appliance can operate at once. A suitable generator and, where needed, load management still have to account for combined demand and starting requirements. Ask the installer to explain what happens if demand approaches the generator’s limit and which loads will be controlled or unavailable.
Fuel choice affects the equipment you can use, how you supply it and how long it can run between refuelling or replenishment. Depending on the generator and what is available at the property, options may include petrol, diesel, LPG or a connected gas supply. Confirm the specific fuel supported by the model and whether the proposed arrangement is practical for your site.
Ask the manufacturer or installer for expected runtime at the load you plan to use. A runtime figure without its associated load and fuel conditions may not reflect your household’s experience. For a portable unit, consider how fuel will be stored and accessed safely. For a fixed unit, confirm what fuel connections or storage arrangements are included in the installation quote and who is responsible for that work.
Place any generator outdoors in a location that follows its manufacturer’s instructions and applicable local requirements. Exhaust contains carbon monoxide, which can be fatal. Never operate a generator indoors or in an attached garage, even with the door open. The installer should consider exhaust direction, openings into the home, ventilation, weather exposure, service access and any relevant clearance or noise requirements when recommending a location.
Also consider how the equipment will be reached for maintenance and refuelling, whether its position could be affected by water or drainage, and how cables and fuel connections will reach the house. A convenient spot is not suitable if it conflicts with the manufacturer’s clearances or creates an exhaust or access problem.
There is no single installation cost that applies to every home. The total depends on the generator type and capacity, transfer equipment, wiring changes, site preparation, fuel arrangements, access and any required approvals or inspections. A fixed installation serving several circuits may involve different work from a portable generator connection serving a limited set of loads.
Request an itemised quote that identifies the equipment and work included. Check whether it covers:
Compare quotes against the same backup plan. A lower price may reflect fewer circuits, different equipment or work that is not included, rather than a like-for-like saving. Ask each installer to state the generator capacity, the loads it is intended to support, how starting demand was considered, and what happens if you later want to add equipment.
For a home in New Zealand, discuss the proposed work with an appropriately licensed electrical worker and ask which approvals or inspections apply to the specific installation. If you are considering financing, compare the total repayment and any fees as well as the payment schedule. Keep financing decisions separate from the technical question of what capacity and installation scope your household actually needs.
Before the installation is complete, ask the installer to demonstrate the transfer process, explain which loads to use first and show how to shut the system down safely. Keep the manuals and operating instructions accessible to everyone who may need them. A planned test and maintenance routine can also help you identify problems before an outage, following the equipment manufacturer’s instructions.
It can supply selected household circuits when connected through a suitable transfer arrangement installed for that purpose. Never connect it through a wall outlet or use an improvised connection to energise household wiring. Ask an appropriately qualified electrical professional to specify the safe arrangement for your home.
Start with the loads you want to run, then account for their continuous demand, starting requirements and which may operate at the same time. Have the proposed capacity checked against the generator’s output ratings and your home’s electrical setup. The right size depends on your intended backup plan, not just the size of the house.
Not necessarily. Selected-circuit backup may be more suitable if you have a short list of essential loads and are comfortable leaving other equipment off. Wider coverage can offer more flexibility, but the generator still needs enough capacity for the loads that may run together.
Runtime depends on the generator, fuel supply and the load being served. Ask for an estimate at the load you expect to use, rather than relying on a figure that does not state its operating conditions. Also plan for safe refuelling or replenishment if an outage lasts longer than the available fuel.
A standby installation can involve electrical connections, transfer equipment, site preparation and fuel work. Have those elements assessed and completed by appropriately qualified professionals, and confirm any local approval or inspection requirements before work begins. Do not attempt to improvise a connection to the home’s wiring.
A sound backup generator installation starts with a realistic list of the loads your household cannot lose, followed by a capacity and transfer plan that supports them safely. Use that plan to compare equipment, fuel arrangements, site requirements and itemised quotes. Before committing, confirm exactly what will run during an outage and what the installation does not include.
