Solar Panel Calculator

Daily consumption, kWh

Peak sun hours

Средняя полоса России: 2-3 зимой, 4-5 летом.

Panel rating, W

Days of autonomy

Advanced options

Bank voltage, V

System losses, %

Result

Panels5
Installed capacity, W2,000
Capacity required, W1,905
Battery capacity, Ah417
Inverter rating, W1,250
Roof area, m²10

From kilowatt-hours a day to a panel count

Sizes the array, the battery bank and the inverter for a given daily consumption.

The starting point is how much energy the house uses in a day. Divide by peak sun hours — not daylight hours, but the equivalent time the panel would spend at full output. In central Russia that is two hours in winter and five in summer.

Then come the losses. Controller, inverter, wiring, dust and panel heating together take about a quarter of the yield, so installed capacity always exceeds what a plain division suggests.

What this calculator shows

Array capacity required and how many panels of your chosen rating that is
Battery capacity for the days of autonomy you want
Inverter rating and the roof area the panels will occupy

What to keep in mind

Lead-acid banks are never discharged past half their capacity, and the sizing reflects that.
Area is estimated at two square metres per panel of around 400 watts.

FAQs

What are peak sun hours?

The equivalent number of hours at 1,000 W/m² irradiance. In central Russia that is 2 to 2.5 in winter and 4 to 5 in summer, averaging about 3.5 over the year.

Why assume 25 percent losses?

The charge controller costs 5 to 10 percent, the inverter another 5 to 10, wiring about two, plus dust and summer heat on the panels. A quarter is the normal total.

How many days of autonomy should I plan?

One is enough for a weekend cabin; two or three for permanent living. Each extra day multiplies the battery bank, which is the most expensive part of the system.

Do solar panels pay for themselves?

Where mains electricity exists at domestic rates, rarely — payback stretches past twenty years. They make sense where there is no grid connection at all, or where getting one costs a fortune.

Worked example

A cabin at five kilowatt-hours a day

Input: 5 kWh a day, 3.5 sun hours, 400 W panels

Output: 1,905 W of array — 5 panels and 417 Ah of batteries

Note: Five panels take about ten square metres of roof. A 417 Ah bank at 24 volts means four 200 Ah batteries weighing over a hundred kilograms.

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Result

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