How to Reduce Your Generator Dependency with Solar and Batteries

Introduction

Running a generator as your primary power source is getting expensive -- and risky given fuel price volatility. A properly designed solar-battery system can dramatically reduce generator runtime by 70-90%, potentially eliminating it entirely for homes, farm buildings, and bach properties.

Four Essential Components

The system requires:

  1. Solar panels -- North-facing arrays deliver approximately 4 peak sun hours in winter and 6+ hours in summer across New Zealand
  2. MPPT charge controller -- Victron SmartSolar controllers are recommended for efficient voltage conversion
  3. Battery bank -- Lithium LiFePO4 batteries provide 80%+ usable capacity versus 50% for lead-acid, with 10+ year lifespans
  4. Inverter/charger -- Converts DC to 230V AC while enabling generator charging during poor weather periods

Sizing Methodology

Two critical measurements determine system specifications:

  • Peak power (kW) -- Maximum simultaneous load; sizes the inverter
  • Daily energy (kWh) -- Total consumption; sizes panels and batteries

A 5kW inverter doesn't require 5kW of solar panels. An 8kWh daily requirement might need only 2-3kW of panels, as they simply need sufficient sunlight hours to charge batteries.

Three System Configurations

Small Systems (3-8kWh/day)

The Victron EasySolar-II GX 48/5000 combines inverter, MPPT controller, and monitoring. Pair with 2x PylonTech US5000B batteries (9.6kWh total) and 4-6x 470W panels. This supports refrigeration, LED lighting, laptops, and Starlink with minimal generator use.

Medium Systems (8-15kWh/day)

Upgrade to Victron Multi RS Solar 48/6000, which includes ground fault protection for permanent installations. Add 15+ kWh battery storage (BYD or PylonTech) and 8-12x 470W panels. The Cerbo GX monitoring unit can divert excess solar to water heating at 95% battery charge.

Large Systems (15-30kWh/day)

Victron Quattro inverters in parallel or three-phase configuration handle serious loads including induction cooktops and workshop equipment. Expect 40+ kWh battery capacity and 15-20kW solar arrays. Generators transition to genuine backup status rather than daily necessity.

Generator Role as Backup

Keeping a generator remains practical for New Zealand winters. Victron inverter/chargers automatically accept generator input and charge batteries without manual intervention.

Key recommendations include:

  • Use pure sine wave generators (Honda brands prove reliable)
  • Victron units can limit input current to prevent small generator overloading
  • Manual-start generators benefit from Cerbo GX monitoring for remote battery status checking

Design Tools

The AnyKit Solar Design Tool is a free online configurator providing complete system specifications including cable sizing, fuse selection, and wiring diagrams in approximately five minutes.

Key Takeaway

Proper solar-battery system design can substantially reduce or eliminate generator dependency while providing cost savings and energy independence for off-grid New Zealand properties.