Free Tool
Off-Grid System Builder
Answer three quick questions and get a complete recommended system: battery bank, solar array, charge controller and inverter, matched to how you will use it.
A complete off-grid system needs four matched parts: a battery bank sized to your daily energy use and days of autonomy, a solar array big enough to recharge it in UK sun hours, an MPPT charge controller rated for that array, and an inverter that covers your appliances plus their start-up surge. This builder sizes all four from your usage in about a minute.
Interactive Tool
Off-Grid System Builder
What will your system power? We will preload typical appliances, which you can edit in the next step.
How this is calculated
The builder starts from your daily energy use: each appliance's wattage multiplied by its hours per day, plus 15% for inverter and wiring losses. Your battery bank is sized to cover that demand for your chosen days of autonomy, divided by the usable share of the chemistry you pick (around 90% for LiFePO4, 50% for lead-acid AGM).
The solar array is sized against UK peak sun hours, from roughly 4.5 a day in summer to just 1.2 in winter, with a 25% real-world derate for panel angle, temperature and cloud. The MPPT controller is matched to the array wattage divided by your bank voltage, and the inverter to your total running load with 20% headroom and an allowance for the largest motor start surge.
Treat the output as a well-informed starting point rather than a final design. For fine-tuning, each figure has its own dedicated calculator: solar and battery sizing, MPPT controllers, inverters and cable sizing.
Frequently asked questions
What does a complete off-grid power system include?
Four core parts: a battery bank to store energy, solar panels to recharge it, a charge controller (usually MPPT) to manage charging safely, and an inverter to turn stored DC into 230V AC for your appliances. Cables, fuses and mounting complete the install.
How much solar and battery do I actually need?
It comes from your daily consumption in watt-hours, your days of autonomy (how long the battery must last with no sun), and UK peak sun hours. The builder works all three out for you, or use the dedicated Solar & Battery Sizing Calculator for a deeper breakdown.
Do I need an MPPT or a PWM charge controller?
MPPT is the right choice for almost all off-grid systems. It harvests 20 to 30 percent more from your panels and handles higher array voltages, which matters as soon as you add more than one panel. PWM only suits very small, low-voltage setups.
Can I start small and expand later?
Yes, if you plan for it. Size your charge controller and inverter with headroom, and choose a battery chemistry (LiFePO4) and voltage you can add to. Mixing old and new lead-acid batteries is best avoided, so plan the bank up front.
