Choosing the size of your system is the most important decision in your solar journey. Go too small and the battery runs flat before dawn while the inverter trips whenever the AC starts; go too big and you've paid for capacity you'll never use. This guide walks through the same method our solar calculator uses, step by step, with numbers from real Iraqi homes.
Step 1: Work out your daily energy use in kWh
List the appliances you want to run on solar, then multiply each one's power in watts by the hours it runs per day. The total is your daily energy use. Typical figures for an Iraqi summer:
- 1.5-ton inverter split AC: about 1,300 W × 10 h ≈ 13 kWh.
- Household refrigerator: about 200 W × 10 h of actual compressor running ≈ 2 kWh.
- Ten LED lights: 15 W × 10 × 6 h ≈ 0.9 kWh.
- TV with satellite receiver: 150 W × 6 h ≈ 0.9 kWh.
- 1 hp water pump: 750 W × 1 h ≈ 0.75 kWh.
A family home with one inverter AC and the usual essentials typically lands somewhere between 15 and 22 kWh a day in summer. Remember that fridges and freezers don't run non-stop: the compressor cycles on and off, so we count its real running hours rather than the full 24.
Step 2: Find your peak load to size the inverter
Inverters are rated in kilowatts and must carry every appliance running at the same moment, plus start-up surges. Anything with a compressor or motor, such as a fridge, a standard AC or a water pump, can briefly draw up to three times its normal power when it starts, while inverter-type ACs ramp up gently without a big spike.
A practical rule: add up the appliances that may run together and choose an inverter about 25% larger. If you're used to thinking in generator amps, each amp at 220 V is roughly 220 W, so 10 A is about 2.2 kW, and a 6 kW inverter gives you the equivalent of around 27 A at once.
Step 3: Decide how many hours the battery must cover
Panels only work in daylight; nights and long outages run on the battery. In mid-July 2026, for example, press reports said Baghdad received only 8–10 hours of grid power a day, meaning outages of 14–16 hours. Estimate the energy you use after sunset, then divide it by the battery's usable depth of discharge.
Example: if you use 9 kWh at night with a LiFePO4 battery at 90% depth of discharge, you need at least about 10 kWh of nominal capacity. If you want a comfortable margin for hot nights or longer AC hours, a 16 kWh battery is the more relaxed choice.
Step 4: Size the panels from peak sun hours
Peak sun hours are the number of hours the sun delivers the equivalent of full 1,000 W/m² irradiance. Across Iraq the annual average is roughly 5.8–6.2 hours a day: about 6.2 in Basra, 6.0 in Baghdad and 5.8 in Nineveh. After heat, cable and inverter losses, each kilowatt-peak of panels yields about 4.6 kWh a day on average.
The formula: array size in kWp = daily energy ÷ (peak sun hours × 0.77). For 20 kWh a day in Baghdad: 20 ÷ (6 × 0.77) ≈ 4.3 kWp, or about seven 620 W panels. If the system also has to fill a large battery, or you want better coverage in winter when sun hours drop to around 3.6–4.6, add extra panels.
Step 5: Check your roof space and orientation
- A modern 600–670 W panel is about 2.3–2.5 m long and about 1.13 m wide.
- In Iraq, panels perform best facing south at a tilt of roughly 28–33°.
- Avoid shade from water tanks, walls and satellite dishes; even partial shade cuts output.
- Leave walkways for cleaning and maintenance, and enough spacing between rows so they don't shade each other.
Common sizing mistakes
- Sizing for summer only: in December peak sun hours drop to around 3.6–4.6, so a system that copes in July may not fill the battery in winter.
- Ignoring start-up surges: a standard AC or water pump can trip a small inverter the moment it starts, even when the total load is below the inverter's rating.
- A small battery for a night-time AC: running the AC at night is the biggest drain on any battery, so work it out carefully before anything else.
- Forgetting the generator line limit: if the inverter will charge the battery from the generator, the charging current must stay within your subscribed amps.
- Leaving no room to grow: choose an inverter that accepts more panels than you install today; the 6 kW Deye SG05LP1, for example, accepts up to 9.6 kW of panels.
Worked example: a family home in Baghdad
A family runs one 1.5-ton inverter AC, a fridge and freezer, ceiling fans, lights, a TV, a router and a water pump. Their summer use is about 22 kWh a day, their peak load about 3.5 kW and their night-time use around 9 kWh.
A sensible recommendation: a 6 kW hybrid inverter, about 6.2 kWp of panels (ten modules) and a 16 kWh lithium battery. That's very close to our 6 kW hybrid home system with 16 kWh storage, which is estimated to produce around 29 kWh a day in average Iraqi conditions.
Skip the maths: use the solar calculator
Our solar calculator does all of this for you. Pick your governorate and it applies the local sun hours and outage hours, add your appliances and running hours, and you get a recommended inverter, battery and panel size with matching products from our store. You can then send the result to our team on WhatsApp to review it with you before you buy.
