Home & DIY
How many kWp and kWh does a rooftop solar system produce?
Annual production, bill savings and payback for a roof-mounted PV system from kWp, orientation, tilt and your electricity price.
Quick answer
Roof solar is the opposite of balcony plug-in kits: you size in kilowatts-peak (kWp), connect through a grid-tied inverter, and your meter spins backward for the kWh you export. Annual production is kWp × your region’s sunshine yield (roughly 950–1,400 kWh per kWp in Europe) corrected for roof direction and slope — south at ~30° is the benchmark everything else is measured against.
Production per year
6,900 kWh
- Annual savings
- ,079.85
- Simple payback
- 11.1 years
- Of typical household use
- ~256%
- Installed power
- 6 kWp
Production = kWp × regional yield × orientation × tilt. Savings mix self-consumed kWh at your retail price and exported kWh at the feed-in rate — adjust self-consumption: ~30–40% without battery, 50–70% with heat pump or someone home midday, 80%+ with home battery. Payback ignores tax credits, maintenance and rising prices — use it as a ballpark. Roof PV needs a qualified installer and grid connection; check local permits and incentives.
How it works
Money saved is not production × your bill rate. A typical home without a battery self-consumes only 30–50% of roof output — the rest is exported at a lower feed-in tariff. That split is why the calculator asks for both retail price and export rate. A 6 kWp system in central Italy might produce ~6,900 kWh/year; at 45% self-use, €0.25/kWh retail and €0.08 export, that is roughly €1,100/year — payback near 10 years on a €12,000 install before tax credits. Incentives, rising power prices and a home battery change the picture; this tool gives the physics and the ballpark economics.
Frequently asked questions
How many kWp do I need for a family home?+
Rule of thumb: annual consumption ÷ regional yield per kWp. A household using 3,500 kWh/year in a 1,150 kWh/kWp zone needs about 3 kWp to match usage on paper — but you rarely cover 100% without oversizing and a battery. Installed sizes of 3–6 kWp are typical for flats and terraced houses, 6–10 kWp for detached homes with heat pumps.
What is the difference between rooftop and balcony solar?+
Balcony kits are small (≤800 W), plug into a socket, and suit renters. Rooftop systems are kilowatts-scale, need professional mounting and grid registration, and export surplus through your utility contract. Roof PV produces far more kWh but costs more upfront.
Is a north-facing roof worth it?+
Usually no for economics alone — production drops to roughly half of south. East/west roofs lose about 15% and still pay back in sunny regions. If north is your only surface, compare the calculator output to your actual consumption pattern or consider other surfaces.
Does this include tax credits or the Italian Superbonus?+
No — incentives change by country, year and income. Use the payback figure as pre-subsidy, then apply your local deduction (e.g. Italian ecobonus percentages) separately. Always confirm current rules with a qualified installer or accountant.
As an Amazon Associate I earn from qualifying purchases — the price does not change for you.
More calculators — Home & DIY
- Balcony solar output
- Paint for walls
- Tiles for floors
- Skirting boards per room
- Cost per meter
- AC size (BTU)
- AC for house / office
- Appliance electricity cost
- Generator size (watts)
- Generator by vehicle/home size
- Lumens per room
- Ant bait quantity
- Dehumidifier size
- Air purifier CADR
- Robot vacuum advisor
- Steam cleaner advisor
- Heat pump vs condenser dryer
- Detergent per load
- Moving van size
- Epoxy resin amount
- Yarn & fabric amount
- Miniature paint amount
- Concrete volume m³
- Deck boards
- Laminate packs
- Plywood sheets
- Pressure washer
- Portable generator
- Dehumidifier
- Moving van
- Forklift
- Mini excavator
- Tractor