How Many kW of Solar Panels Do You Need? Size It by Your Bill

The answer to how many kW of solar panels you need comes from two numbers: your annual electricity consumption and the annual specific yield of your location. For central Antalya, PVGIS (European Commission JRC) shows that 1 kWp produces about 1,656 kWh a year, assuming optimum tilt and south orientation. So when you divide your annual consumption by 1,656, you get approximately the system power (kWp) that covers your need. In this article we show the formula with examples and explain the factors that change the result and the official limits.

How many kW of solar panels do you need? The basic formula

The calculation takes three steps:

1. Find your annual consumption: Add up the kWh values on your last 12 months of bills. Do not look only at a summer or winter bill; in Antalya the seasonal difference is large because of air conditioning.
2. Divide by the specific yield: Required kWp = annual consumption ÷ 1,656.
3. Convert to panel count: Required kWp ÷ panel power (kW). For a 605 Wp panel, divide by 0.605 and round up.

There is also a simple rule of thumb: a 605 Wp panel produces about 0.605 x 1,656 = 1,002 kWh a year in Antalya. So dividing your annual consumption by about 1,000 gives you the panel count. This rule is only for a first estimate; it does not account for roof orientation or shading.

Worked examples by bill consumption

The table below shows the required system power starting from average monthly consumption values. Panel surface is calculated for 605 Wp panels of 2278x1134 mm; layout gaps are not included.

For example, a detached house consuming 600 kWh a month needs 7,200 ÷ 1,656 = 4.35 kWp. Seven panels at 4.24 kWp fall slightly short of the need; 8 panels at 4.84 kWp exceed it. Which to choose depends on roof area and your goal. For a comparison of sizes at home scale, see our 3, 5 and 10 kWp comparison.

How many kW of solar panels do different home types in Antalya need?

The consumption profile varies markedly by home. 2+1 or 3+1 flats in Muratpaşa and Kepez often consume in the 250-400 kWh a month band; a 2-3 kWp system is often enough for such a flat, but on an apartment roof, space and the decision of the unit owners are decisive. In detached homes in Aksu, Döşemealtı and Kepez, monthly consumption can reach 500-800 kWh and systems of 4-6 kWp come into play. In villas in Konyaaltı, Belek and Manavgat, air conditioning, a pool pump and many appliances run together, so calculations of 10 kWp and above are common. These ranges are examples; they are no substitute for your own bill data.

The installations that Solar Nexo shared on Instagram show this variety: in Manavgat, 20 panels of 605 W (12.1 kWp) with a 15 kW hybrid inverter; in Belek, 24 panels of 605 W (14.52 kWp) with a 20 kW hybrid inverter; and in Döşemealtı, 36 panels of 605 W (21.78 kWp) with a 20 kW hybrid inverter. Each was calculated separately for that home's roof, consumption and battery need.

Factors that change the result

Orientation, tilt and shading

The 1,656 kWh/kWp value applies to a surface that is south-facing at a 33° tilt. If your roof faces east or west or has a low pitch, production falls and more kWp is needed to cover the same consumption. Shadows from a nearby building, tree or chimney have a similar effect. For details on angle and orientation, see our article on the solar panel angle and orientation for Antalya.

Losses and real production

The PVGIS value includes 14% system loss; however, factors such as dirt, cable loss, inverter efficiency and temperature can give a different result in the real field. In Antalya, ambient temperature is high in summer; the temperature coefficient is −0.30 %/°C in TOPCon panels versus about −0.34 %/°C in PERC. Panel choice therefore also indirectly affects the required power calculation.

Seasonal distribution

A balance over the year does not mean every month is in balance. According to PVGIS, 1 kWp in Antalya produces 99 kWh in December, 99 in January, 168 in July and 167 in August. A 4.84 kWp system produces about 813 kWh in July and about 479 kWh in December. If your air-conditioning load is heavy in summer, production and consumption overlap well; if your winter consumption is high, purchases from the grid continue in those months.

How many kW of solar panels do you need: should the goal be all of your consumption?

Not necessarily. For installations connected to a residential subscription, no generation or sales limit applies and net metering is done monthly; surplus is valued at the single-rate active energy unit price of the relevant tariff. Because this price is lower than the total unit charge on the bill, sizing the system far above your consumption is economically less efficient. On the other hand, choosing too small a system is often inefficient too, because you spread the roof and infrastructure cost over fewer kWp.

The capacity ceiling is your contract power; the system power cannot exceed it. Rooftop systems up to 25 kW benefit from the simplified procedure. For non-residential installations, hourly net metering applies from 1 May 2026 and annual production cannot exceed twice the annual consumption of the associated consumption facilities. The right size for a business is therefore determined by its hourly load profile. For the business approach, see our article on rooftop solar investment. These rules are based on texts in force as of October 2026 and may change; verify the current conditions with the distribution company before applying.

How many kW will fit on the roof?

The kWp you calculate may not fit on the roof. As a rough measure, 1 kWp needs about 4.3 m² of panel surface alone; maintenance walkways, roof protrusions and shading distances mean not all of the usable area can be given to panels. On tile roofs in Antalya, the pitch allows panels to be placed directly parallel to the roof. On flat roofs, if a tilted structure is used, a shading distance is needed between rows and less kWp fits in the same area. The load-bearing capacity of the roof needs to be assessed by a civil engineer; the distribution company and the municipality may ask for a structural suitability certificate.

Sizing differs for battery and off-grid systems

In grid-connected systems, sizing from the annual total is a sufficient starting point. In off-grid or battery systems, the worst month (December or January, 99 kWh/kWp) is the basis, because if winter production does not cover consumption the system runs out of energy. Battery capacity and night-time consumption are calculated separately. We covered this in more detail in our article on solar systems with batteries.

Common mistakes in sizing

• Looking at a single month's bill: A July bill can be high because of air conditioning and an April bill low. The annual total is always more reliable.
• Forgetting losses: Calculating production with the ideal values in marketing brochures instead of 1,656 makes the system look smaller than it needs to be.
• Not checking contract power: If the calculated kWp is larger than your contract power, the application is limited by capacity.
• Not allowing for future loads: If a pool, a second air conditioner or new appliances are added later, the system will be too small.
• Focusing only on panel count: Inverter power and roof layout also determine the result.

Step-by-step preliminary calculation checklist

• Add up your last 12 months of bill consumption.
• Note any loads to be added in future (air conditioning, pool pump, electrical appliances).
• Divide the total by 1,656 and calculate the panel count.
• Check roof orientation, tilt and shading.
• Verify your contract power from your subscription document.
• Confirm the calculation with an engineer at the free survey.

For a quick preliminary calculation, you can use our solar energy calculation tool.

Conclusion

You can answer how many kW of solar panels you need approximately by dividing your annual consumption by 1,656; however, the final decision should be made on roof area, shading, contract power and your usage habits. At the free survey, Solar Nexo measures your roof on site, examines your consumption profile and firms up the sizing with an engineering calculation.

#Cost and Investment#How Many Kw#Sizing#Bill Calculation#Kwp Calculation