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Guides

Plain-language explanations of the numbers behind backup power, so you can plan a system and judge a quote.

Planning a system

How many solar panels do I need? A simple method that works anywhere
Work out how many solar panels you need from your daily energy use, your local peak sun hours and the panel size, with worked examples.
How long will my battery last? Working out backup runtime
Work out how many hours a battery bank will run your appliances, using usable capacity, inverter losses and your real load, with worked examples.
How to find out how many watts your appliances use
Where to find an appliance's wattage, how to work it out from volts and amps, and why fridges and air conditioners need special care.
Peak sun hours: why your dullest month decides your solar size
What peak sun hours are, how much they vary from Phoenix to London, and how to use them to size solar panels that keep up all year.
Inverter and battery vs generator: how to compare the real cost
A simple method to compare what your generator really costs with a battery or solar system, using your own fuel, running hours and quotes.
Backup power and solar for a small business or shop
How shops, salons, offices and small workshops can size backup power: list business-critical loads, match solar to opening hours and avoid oversizing.
12 questions to ask a solar or inverter installer
What to ask before you pay for an inverter, battery or solar system, and the answers that should make you walk away.

Lithium vs lead-acid batteries for backup power
How lithium (LiFePO4) and lead-acid batteries compare on usable capacity, lifespan, charging and cost per cycle, and when each makes sense.
How long does it take to charge an inverter battery?
Work out how long a backup battery takes to recharge from the grid, a generator or solar, and why the last part of a lead-acid charge is slow.
12 V, 24 V or 48 V: choosing a battery system voltage
Why bigger backup systems use higher battery voltages, how voltage affects current, cables and safety, and which voltage suits your system size.
How to make your backup batteries last longer
Practical care for lithium and lead-acid backup batteries: depth of discharge, charging, heat, ventilation, storage and the mistakes that shorten their life.

kVA vs kW: what an inverter's rating really means
Why a 5 kVA inverter may only run 4 kW of appliances, how to read the spec sheet, and how much headroom to leave.
Hybrid, off-grid and grid-tied inverters: which one do you need?
The three kinds of solar inverter explained, why a grid-tied system usually goes off in a power cut, and which suits a home that needs backup power.
What size generator do I need? Running and starting watts
Size a generator for your home or for charging backup batteries: running and starting watts, kVA ratings, load levels and safe connection.
Pure sine wave vs modified sine wave inverters
What the waveform means, which appliances need a pure sine wave inverter, and when a cheaper modified sine wave model is good enough.
MPPT vs PWM charge controllers: which one do you need?
How MPPT and PWM solar charge controllers differ, why MPPT harvests more energy from modern panels, and how to size a controller.

Can I run an air conditioner on an inverter and solar?
What it takes to run an air conditioner on batteries and solar: inverter size, starting surge, energy per night and the choices that make it affordable.
Running a fridge or freezer on an inverter or solar
How much energy a fridge really uses, why its starting surge matters, and how long food stays cold during a power cut.
Running a water pump on solar or an inverter
Two ways to run a water pump without the grid: through your backup inverter, or with a dedicated solar pump and a tank. How to size each.