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Current, voltage, AC vs DC — the mental model everything else hangs on
Think of electricity as water in pipes. Voltage (V) is the pressure pushing it; current (amps, A) is the flow rate; power (watts, W) is pressure × flow — what actually gets work done. A thin pipe (thin cable) under high flow gets hot; that's why cable sizing matters.
Electricity comes in two flavours. DC (direct current) flows one way, steadily — it's what panels make, batteries store, and electronics ultimately use. AC (alternating current) reverses direction 50 times a second in the UK — it's what the grid delivers and wall sockets provide, because AC travels long distances efficiently.
One more idea unlocks system design: series vs parallel. Connect two 12V panels in series and voltages add (24V, same current); in parallel, currents add (12V, double current). Same energy, different shape — and your charge controller cares which.
You don't buy "electricity", but you do buy into a system voltage, and it's the first real decision in any build. The DIY world standardised on 12V (huge ecosystem of campervan/marine kit), 24V (half the current of 12V for the same power — thinner cables, better for ~1kWh+ daily use), and 48V (whole-home territory). UK mains is fixed at 230V AC, 50Hz — the thing your inverter imitates.
Rule of thumb from the field: under ~1.5kWh/day, 12V keeps everything cheap and compatible; above it, 24V saves real money on copper.
Every choice downstream — cable thickness, fuse ratings, which battery, which inverter — flows from two numbers you establish first: your daily energy (Wh) and your system voltage. Get the mental model right and spec sheets stop being intimidating; they're just pressure, flow and work.
From EcoPowerful — plain-English DIY solar & wind guidance for UK homes, with a free instant system plan builder. Guidance is general; 230V fixed wiring always needs a qualified electrician. Last updated 2026-06-13.