List what you want to run and for how long, and get the panels, inverter and batteries you actually need. Sized on winter sunlight rather than the annual average, and corrected for the heat that costs an Iraqi rooftop array a sixth of its output in July.
Tap the things you need, then set how many hours a day each one actually runs. Hours matter more than watts here — a 1500 W air conditioner running 8 hours costs far more panels than a 2000 W kettle running 10 minutes.
These two answers decide almost the whole cost. Batteries are the expensive part of any solar system, so the honest answer to the second question saves real money.
Sunlight and heat both depend on where you are, and heat is the part most quotations quietly ignore.
This is the system your list needs. Send it to us for a price, or go back and change the backup hours to see how much the batteries move the total.
This calculator gives an indicative system size for budgeting and comparing quotations. It is not a design document. Array, inverter, battery and protection selection must be confirmed by a qualified engineer using site-specific irradiance data, the actual module and battery datasheets, a shading survey, and the wiring and structural rules that apply at your site. Roof loading and DC-side arc-fault risk are outside the scope of this tool. Mega Standard accepts no liability for decisions made on these figures alone.
Peak sun hour figures are regional approximations for Iraq, not site measurements. For a final design, use a site-specific irradiance dataset such as PVGIS or NASA POWER, and the actual temperature coefficient from your module's datasheet.
A solar system is sized by energy, not by power. What matters is not how many watts a device draws but how many watt-hours it consumes in a day, and that is watts multiplied by hours.
A 2000 W kettle is the biggest number on most people's list, but it runs ten minutes a day — about 0.33 kWh. A single 1500 W air conditioner running eight hours consumes 12 kWh, thirty-six times more. The kettle barely affects the array; the air conditioner defines it.
This is why the hours column on the previous step is the one worth getting right. Guessing high on hours is the fastest way to double a solar quotation.
Sunlight in Iraq varies enormously by season. Central Iraq gets roughly 7.5 peak sun hours on a long June day and about 3.6 in December — the array produces less than half as much in winter as in summer.
That creates a fork in the design:
This is the single biggest reason two solar quotations for the same house can differ by 40 %. It is worth asking any supplier which month they sized on.
A solar panel's rated wattage is measured at 25 °C cell temperature. Cells are not the air around them — in still conditions they run roughly 25 °C hotter than ambient. On a 45 °C Iraqi afternoon that puts the cells near 70 °C.
Crystalline silicon loses about 0.4 % of its output for every degree above 25 °C. At 70 °C that is roughly an 18 % loss, before any dust, wiring or inverter losses are counted.
Array kWp = daily kWh ÷ (peak sun hours × derate) derate = (1 − soiling/wiring/inverter) × (1 − temperature loss) temperature loss ≈ 0.004 × (cell temp − 25) cell temp ≈ air temp + 25
The practical consequences are worth knowing. Mounting panels flat against a roof traps heat and makes this worse; leaving an air gap underneath measurably helps. And a panel with a better temperature coefficient — the figure on the datasheet, typically −0.29 %/°C to −0.45 %/°C — is genuinely worth more in this climate than the same wattage from a cheaper module.
Panels have become inexpensive. Storage has not, and it is the part that wears out. Every extra hour of autonomy adds capacity that sits unused for most of the year.
Usable capacity is not nameplate capacity. A lead-acid bank should not be discharged below about half, so a 10 kWh lead-acid bank gives you around 5 kWh. Lithium can be taken to roughly 90 %, so a 10 kWh lithium bank gives about 9 kWh. Comparing the two on nameplate kWh is comparing the wrong number.
Heat shortens battery life too. Lead-acid loses about half its life for every 10 °C above 20 °C, so a bank in an unconditioned room in Basra may last a small fraction of its rated years. Lithium is far more tolerant but not immune.
On a site that already has a generator, the cheapest reliable answer is usually a modest battery bank for the evening plus the generator for genuinely bad days — not a battery bank sized to survive two days without sun.
It depends on your daily energy use in kWh, not on the size of your house. List what you run and for how long above and the calculator gives you the array size, panel count and roof area. As a rough guide, a home using 20 kWh a day off-grid in central Iraq needs somewhere around 7 to 8 kWp of panels.
Yes, but it is usually the load that decides the whole system size. A 1500 W air conditioner running eight hours uses about 12 kWh a day, which on its own needs roughly 4 to 5 kWp of panels off-grid. An inverter air conditioner uses considerably less than a fixed-speed one and often pays for itself in the solar system it saves.
Take the share of your daily energy you use after dark, divide it by the usable depth of discharge of your battery type — about 0.9 for lithium, 0.5 for lead-acid — and allow for inverter losses. This calculator does that for you. Note that a lead-acid bank needs roughly twice the nameplate capacity of a lithium one for the same usable energy.
In this climate, usually yes. Lithium gives nearly twice the usable capacity per nameplate kWh, tolerates heat far better, and lasts several times as many cycles. Lead-acid in an unconditioned room in an Iraqi summer can lose half its life for every 10 °C above 20 °C, which often means replacing the bank far sooner than the purchase price suggested.
No. It gives a defensible size for budgeting and for comparing quotations. A real design needs site-specific irradiance data, a shading survey, the actual module and battery datasheets, roof structural checks and DC-side protection design. Those are a qualified engineer's job.
We supply solar panels, hybrid inverters, lithium and lead-acid storage and the switchgear that goes with them, across Iraq. Send us the result and we will come back with a specification and a price — and tell you honestly if fewer batteries and a generator would serve you better.