What your home draws, what it costs, and whether panels would pay for themselves
Almost nobody knows what their home actually uses, because a bill arrives as one number with no breakdown. Adding it up appliance by appliance is a corrective, and the result is usually surprising in both directions. The things people worry about — a phone charger left in the wall, a television on standby — turn out to be pennies a year. The things that matter are the ones that make heat or move it: water heating, space heating and cooling, an electric oven, a tumble dryer. In most homes a handful of appliances account for the large majority of the bill, and everything else together is a rounding error.
Whether panels pay for themselves comes down to four numbers, and only one of them is about the panels. How much sun the roof gets, which varies by more than two to one between northern Europe and the tropics; what the electricity being displaced costs, which varies by more than ten to one between countries; how much of the output is actually used rather than exported for a pittance; and what the installation costs, which has fallen roughly ninety per cent since 2010 and still differs by a factor of four between markets. A system that pays for itself in five years in one country can take twenty-five in another with identical hardware.
Two things are worth saying plainly. Cutting consumption is almost always cheaper than generating more: insulation, a heat pump instead of resistive heating, and drying clothes on a line will usually beat the same money spent on panels. And leaving the grid entirely is a different proposition from putting panels on a roof — it needs enough battery to carry the darkest week of the year, and enough extra panel area to refill that battery in midwinter, which is typically several times the cost of a grid-connected array. For most households the sensible answer is panels plus a grid connection, not panels instead of one.