Planning an off-grid solar system starts with a list, not a shopping basket: work out what your household actually uses, then size generation and storage to match.
Step 1: Do an energy audit
Before you buy panels or batteries, list every electrical device you plan to use. For each one, note its power in watts and the average hours it runs per day. Multiply watts by hours to get watt-hours per day, then add them all up for your daily total.
The book gives rough examples of daily use: LED lighting about 30 to 60 Wh, a refrigerator 200 to 400 Wh, a laptop 100 to 200 Wh, phone charging 10 to 20 Wh, a water pump 200 to 500 Wh and a washing machine 150 to 250 Wh. It describes a modest off-grid home as commonly using about 1,500 to 3,000 Wh (1.5 to 3 kWh) a day. Treat those as illustrations and use the labels on your own appliances, because real figures vary.
Step 2: Know the four main parts
- Panels turn sunlight into electricity.
- Charge controller regulates what goes into the batteries so they are not overcharged.
- Battery bank stores energy for the evening, night and cloudy spells (see solar battery storage basics).
- Inverter converts the stored power into the kind of electricity ordinary appliances use.
Step 3: Size the system from your use and your sun
System size depends on your daily consumption and the peak sun hours at your location. For a modest home, the book suggests a starting system of roughly 1,000 to 2,000 watts of panels with 4 to 8 kWh of battery storage. That is a starting point for planning, not a finished design, so check it against your own audit and your local winter conditions. The worked sizing sketch in solar power for beginners shows how the pieces fit together.
Step 4: Choose equipment sensibly
The book recommends monocrystalline panels for off-grid systems: they cost a little more than polycrystalline but give more power per square foot, which matters when roof or ground space is limited. It also advises buying from established manufacturers and looking for a warranty of at least 25 years. A well-designed system, it says, can power a comfortable home for 20 to 25 years with only minor repairs and replacements.
Before you commit
- Separate essential loads from nice-to-have ones, and see how much you can reduce demand first.
- Decide how you will cover the darkest weeks, whether with extra panels, another source or a backup generator.
- Check local electrical rules before installing anything.
Worked example: a small household
These are illustration figures, not a design. Take four loads: six 10 W LED bulbs for 5 hours (0.30 kWh), a fridge-freezer averaging about 50 W over 24 hours (1.20 kWh), a 750 W pump for 1 hour (0.75 kWh) and phone and laptop charging (0.28 kWh). That is 2.53 kWh a day.
- Panels at 4 peak sun hours: 2.53 ÷ (0.4 kW × 4 × 0.8) = 1.98, so 2 panels of 400 W.
- Panels in a dull month at 2 peak sun hours: 2.53 ÷ (0.4 × 2 × 0.8) = 3.95, so 4 panels. This is why winter, not summer, sets the size.
- Two days with no sun: 2.53 × 2 = 5.06 kWh of usable energy.
- Battery size: if the usable share of the battery is 80%, 5.06 ÷ 0.8 = 6.3 kWh nominal. Take the real usable share from the battery’s datasheet.
The 0.8 is a planning allowance for 20% losses in wiring, controller, inverter, heat and dirt; real losses vary. Try the power calculator or fill in your own appliances on the worksheet in the free starter planning pack.
Sources and further reading
- PVGIS: free solar radiation and photovoltaic estimates for your location, from the European Commission.
- Have a qualified electrician design or check any installation, and follow local electrical rules.
Where the books cover this
Chapter 5, “Your Off-Grid Energy System”, covers normal daily energy uses, solar, wind and micro-hydro power, and generator use. The same chapter text appears in both books (see the comparison), so you only need one. Some examples use US units and US organisations, so check how they apply where you live. You can read sample pages before buying.
Off Grid Survival for Beginners · The Off-Grid Survival Manual
If you are mapping out your whole energy plan, the Off-Grid Energy Systems guide pulls the chapter together. For the full walkthrough across power, water, food and shelter, see Off Grid Survival for Beginners.