Solar power for home can lower the amount of electricity you buy from the grid, but the right system depends on when your household uses power, how much of the roof is suitable and what you plan to do with surplus generation. Start with your electricity data and a roof assessment, then compare system sizes, inverter options and battery costs. In New Zealand, also ask how grid connection, exported electricity and local installation requirements will be handled. A smaller, well-matched system may suit your needs better than filling every available roof area with panels.
Gather at least a year of electricity bills, if available, and look for your household’s consumption in kilowatt-hours (kWh). Bills show how much electricity you use over time; interval data from your retailer can reveal when you use it. That timing matters because solar panels generate during daylight, while many homes use more electricity in the morning and evening.
List major loads and consider any changes you expect over the next several years. An electric vehicle, heat pump, induction cooktop or change in the number of people at home could alter your consumption. Don’t size a system solely around a possible future appliance, but ask the designer to show how that addition would affect the recommendation.
Solar electricity used in the home can displace electricity you would otherwise buy. Power sent to the grid may receive an export payment, but the rate and terms depend on your retailer and plan. Since exported power may be valued differently from electricity bought from the grid, a system that produces more than your home can use is not automatically the most economical choice.
A solar assessment should consider more than the roof’s total area. The usable space, direction, pitch, shading, condition and position of vents or other obstructions all affect the layout and expected generation. In New Zealand, a roof facing north often supports strong annual solar production, while east- and west-facing sections may produce at different times of day. The best arrangement depends on the property and household use, not orientation alone.
Ask the installer to identify shaded areas and explain how shading affects the proposed layout. Trees, neighbouring buildings, chimneys and roof features can reduce output. A proposal should use site-specific assumptions rather than treating every roof as equally productive.
Roof condition matters because panels are intended to remain in place for years. If repairs or reroofing are likely, compare the timing and cost of doing that work before installation with the disruption of removing and reinstalling a solar array later. Ask how panels will be fixed, how roof penetrations will be managed and who is responsible if installation work causes a leak.
System size is commonly described by the panels’ combined rated capacity in kilowatts (kW). That number is not the same as the electricity generated over a year, which is measured in kWh. Actual production depends on the site, panel layout, shading, equipment and weather. Ask for an estimate based on your roof and explainable assumptions, including how much generation is expected to be used at home and how much exported.
Compare at least two proposed sizes if the roof can accommodate them. A smaller system may have a lower upfront cost and a higher proportion of power used directly in the home. A larger one may make sense if daytime demand is substantial, an electric vehicle can be charged during sunny hours, or export terms are favourable. The extra panels should have a clear purpose rather than being included simply because there is room.
| System approach | May suit | Main advantage | Trade-off to examine |
|---|---|---|---|
| Smaller grid-connected system | Homes with modest daytime use or a tighter budget | Limits the initial outlay and can match regular daytime loads | May cover a smaller share of total consumption |
| Larger grid-connected system | Homes with significant daytime demand or planned electrification | Can produce more electricity when household loads are operating | More surplus may be exported, depending on usage and season |
| Solar with battery storage | Homes that value using more solar after sunset or want specified backup capability | Stores some daytime generation for later use | Adds cost, equipment and design requirements; savings depend on use and tariffs |
Use the table as a starting point, not a substitute for a production estimate. Ask the installer to state the expected annual generation, the assumptions behind it, and the estimated split between electricity used on site and exported. Have the same assumptions applied to each quote so you can compare proposals fairly.
The inverter converts the panels’ direct-current electricity into alternating-current electricity used by household circuits. Its design affects monitoring, how the array responds to different roof conditions and whether battery storage can be added or integrated.
| Inverter approach | How it works | Potential fit | Question to ask |
|---|---|---|---|
| String inverter | One central inverter serves a group, or string, of panels | A relatively simple roof layout with similar panel conditions | How will shade or different roof orientations affect the string? |
| Microinverters | Conversion equipment is fitted at individual panels | Some roofs with several orientations or panel-level shading concerns | What are the costs, monitoring details and replacement arrangements? |
| Hybrid inverter | Designed to work with solar and compatible battery storage | Households installing a battery now or planning one later | Which battery models are compatible, and what would adding one require? |
These are broad categories, not a ranking. A system with module-level equipment can help address particular layout constraints, but it is not automatically the best choice for every roof. Ask for the proposed model numbers, warranty terms, monitoring features and expected maintenance arrangements. If a battery is a future possibility, confirm compatibility in writing; “battery-ready” can mean different things in different proposals.
A battery stores some solar generation for use later, often in the evening. It can increase the share of solar electricity used at home, but its value depends on how much surplus the panels produce, when the household needs power, the battery’s usable capacity and the difference between electricity import and export rates.
Compare the battery’s added cost with the value of the energy it may shift to later use. Request an estimate with and without storage, using your household’s consumption pattern and the retailer’s applicable rates. Include the battery warranty, expected operating limits, inverter compatibility and any costs that may arise if equipment needs replacement. A battery that is too large for the available surplus may not be well utilised.
Backup during an outage is a separate design question. A standard grid-connected solar system may shut down when the grid is unavailable; panels and a battery do not automatically keep the whole home powered. If backup matters, ask which circuits can be supplied, whether the system is designed to operate safely during an outage, and how long the chosen loads might run under the stated assumptions.
Compare the complete installed cost, not just the panel price or headline system size. Check what each quote includes: panels, inverter, mounting hardware, electrical work, monitoring, grid-connection steps, any battery, and the treatment of GST. Ask whether extra work could be charged separately if the site assessment identifies a complication.
Estimate savings from electricity you no longer need to buy, plus any payment for exported power, then account for ongoing charges and the system’s upfront cost. Your electricity bill may not disappear: fixed charges and power drawn from the grid when solar generation is insufficient can remain. Savings will vary with household use, system performance, retail plan and export terms.
For a simple payback estimate, divide the net upfront cost by estimated annual bill savings. Treat the result as a planning tool, not a guarantee. It does not automatically account for financing costs, maintenance, equipment replacement, changing electricity rates or the value of electricity used at different times. Ask the installer to show the assumptions and avoid relying on a payback estimate that leaves them unexplained.
If you are considering finance, compare the total amount repaid, interest, fees, loan term and any conditions—not only the monthly payment. A longer term can make payments feel more manageable while increasing total borrowing costs. Check whether any incentive, grant or financing offer actually applies to your property and system; don’t assume support is available or include it in your calculations until its terms are confirmed.
Request written proposals that use the same household consumption information and clearly identify the equipment. A useful quote explains the proposed layout, estimated generation, expected self-use and exports, inverter choice, battery assumptions and installation scope. If two estimates differ substantially, ask what drives the difference rather than comparing only the total cost.
Installation requirements can depend on the property and the work involved. Ask the installer whether any local council consent or other approval is relevant to your project, and get the answer in writing. Before signing, make sure the proposal describes the connection process and does not assume that exported electricity will be paid at a particular rate without checking your retailer’s terms.
Keep the final system design, equipment details, warranties, commissioning records and installer contacts together. Make sure you know how to read the monitoring app or display and what normal operation looks like. If generation appears unexpectedly low, check for an outage, a monitoring issue or an obvious obstruction before arranging service; don’t climb onto the roof to inspect panels.
Review your electricity plan after the system is operating. Retailer export arrangements and import pricing can affect the value of the power you send to the grid, so compare plan terms using your actual usage and generation pattern. Also revisit the system’s performance if your household changes, such as adding an electric vehicle or shifting more activity into daylight hours.
A well-planned solar system begins with a clear picture of your roof and electricity use. Compare proposals on expected self-consumption, equipment, installation scope and total cost, then add a battery only if its role and economics make sense for your household.
Usually, a grid-connected home may still use electricity when panels are not generating enough, and fixed charges may remain. The amount of the bill reduction depends on when you use power, the system’s output, your electricity plan and any export payment.
It depends on the cost of storage, your evening use, available daytime surplus and the value of exported electricity. Compare a solar-only proposal with a battery proposal using the same household data, and confirm what adding storage later would require.
Not necessarily. Many grid-connected systems shut down during an outage, and backup requires equipment and configuration designed for that purpose. Ask which circuits would remain available and what limits apply to the backup system.
Compare the same proposed system size, estimated annual generation, expected self-use, export assumptions and installation scope. Check the named equipment, warranties, exclusions, connection responsibilities and total cost rather than relying on a headline price alone.
Often, but a new major load can change how much solar electricity your home can use and whether the existing system is large enough for your needs. Tell the designer about planned electrification before purchase and ask how it affects the recommended size and expected savings.
