How to use the solar calculator
- Enter your monthly electricity use and available area, then choose the rate class (low or high voltage) and orientation.
- You can change panel rating (W), area per panel, average daily sun hours and install cost to match a real quote.
- Read the number of panels, area, monthly generation, savings and payback in the result. If area is short, the result is recalculated for the limited panel count.
How generation and savings are calculated
Monthly generation for one panel is "rated power (kW) × daily sun hours × orientation factor × 30.4 days". A 450 W panel with 3.3 hours a day makes about 45 kWh a month, so a home using 350 kWh a month needs about 8 panels to cover it all. If one panel is about 2 m², you need about 16 m².
Savings are the bill before installation minus the bill after. Residential tariffs are progressive, with higher rates for higher usage, so households that use more save more from the same generation. A home using 350 kWh that generates 150 kWh cuts the expensive upper tier first and the bill falls sharply. The tool includes base charge, energy charge, climate fee, fuel adjustment, VAT and fund.
What to check before installing
Generation depends heavily on orientation, tilt and shade. South-facing at about 25 to 35 degrees is favorable, and shade from nearby buildings or trees reduces output a lot. Balcony railing systems are mounted vertically and produce less than roof systems. Check shadows at different times across the year before installing.
On cost, look at your actual spend after government and local subsidies, inverter replacement costs and panel degradation of about 0.5% a year. For rented homes and apartments, check building rules, structural safety and the utility grid connection process first. Get site surveys and quotes from at least two or three installers to compare.
Ways to increase savings
- Run daytime appliances such as laundry, dishwashers and charging during generation hours.
- If you sit across a tier boundary, cutting usage first can beat installing.
- Wipe dust and leaves off the panel surface from time to time.
- Check the installer's after-sales inspection and warranty period.
- Compare quotes on the same per-kW basis.
FAQ
How many kWh does one panel make a month?
A 450 W panel producing about 3.3 hours a day makes roughly 45 kWh a month. Average sun hours in Korea range from about 3 to 4 hours depending on region, season, direction, tilt and shade. You can change the value in the tool to test.
What happens to surplus electricity?
For small solar systems contracted with the utility, net metering usually carries surplus to the next month and subtracts it from usage. This tool conservatively does not count generation above your usage as savings. The real settlement depends on your contract, so ask the installer or utility.
Are subsidies included?
No. Government and local subsidies for home and balcony solar differ by region and year. Enter a lower install cost yourself to see the payback after a subsidy.
Notes & limitations
This calculator makes a rough estimate with average assumptions and is neither an installation quote nor investment advice. Real generation, cost, subsidies and tariffs vary by region, time and contract, so get an on-site quote from a professional installer.