Solar calculator

Is Solar Power Right for Your Home?

With payback periods of 8 to 10 years for the average home installation, electricity from solar cell panels can still provide many years of free electricity , and also doesn’t create any pollution or harmful emissions. Cooking, heating, and operating large tools and clothes dryers may still require the need for traditional forms of power, though solar power users find that the significant reduction in their energy bills makes the investment more than worth it. Solar systems can provide adequate electricity to power most essential household items, such as:

  • Refrigerators and freezers
  • Lights and kitchen appliances
  • Hair dryers
  • Washing machines and dishwashers
  • Television, video, audio equipment and computers
  • Medium sized power tools


While Government subsidies for the adoption of a solar system are not available in New Zealand, it is possible to sell the power that you don’t use back to willing power companies.


In order to ensure you get a good return on investment or ROI you should carefully calculate your solar system size.  You do not want to oversize it, or purchase the wrong equipment  and then have to buy the right equipment. Generally you should aim for covering about half of your power bill.  Using our calculator or other ones will assist you in getting a nice return rather than relying on feed in tariffs and diverters sending it to hotwater systems.  Just keep it simple and design it smaller at first, then upgrade later with the savings. 


Use this calculator as an approximate guide.  *note*  Solar Direct is not suggesting this sizing calculator to be used for financial guarantees of system performance that you will obtain from the solar system sizing you choose using our calculator.   Solar Direct makes no warranties on how well your solar equipment will perform and this is a guide only to assist you in choosing an approximate correct size of your solar system.  Please verify your own size selection as Solar Direct simply provides the products you order and in now way limits or restricts the amount of equipment you order.  If you wish to gain a more accurate exact sizing please purchase our engineering service and add to your cart, we will then contact you and discuss in person with you for more exact customized sizing.  This calculation will target approximately 50% of your power usage being used during the day in somewhat of a conservative fashion and includes your hot water cylinder being a part of the same meter as your solar power in on and using a traditional usage curve of using more power in the winter than in the summer. It also includes a feed in tariff of .8 cents per kw fed back to the grid of the excess power you dont use that is generated during the day on average.  We use Niwa weather data and Auckland for average sun collection hours and an averaged  sun intensity.  30 degree pitch and due north direction of the solar panels. 

Annual power usage/ Solar system size in KW

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