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Energy & Sustainability

Solar Energy Calculators & Guides

Plan, size and understand a solar installation — from panel output to payback and battery storage.

Solar photovoltaic (PV) systems have moved from niche to mainstream, but the numbers behind them stay unfamiliar for most homeowners. How many kilowatt-hours will a 6 kWp array actually produce in your location? How does panel degradation cut lifetime output? How large should a battery be to store what you generate? This hub answers those questions in plain language, with the same math your installer uses.

Every guide here starts with the physical relationships — irradiance, panel efficiency, inverter losses, temperature coefficients — and then translates them into practical decisions: system sizing, roof orientation, and realistic payback horizons. If you are comparing installer quotes, use the linked calculators and articles to sanity-check the assumptions before you sign anything.

Solar rarely stands alone. Rooftop PV pairs naturally with home battery storage, heat pumps that shift consumption to daylight hours, and EV charging that soaks up midday surplus. The guides in this pillar cross-link to those neighbouring topics so you can plan a whole-home energy strategy, not just a single component.

Flagship calculator · Free

Solar Payback Calculator

Project year-1 savings, simple payback, 25-year lifetime return, LCOE and CO₂ avoided — with editable yield, self-consumption and price inflation.

Open calculator

Guides in this hub

In-depth articles covering the math, the assumptions, and the practical decisions for solar energy.

Solar panels installed on residential rooftop generating clean energy
🌱Energy & Environment

How to Calculate Solar Panel Output and Savings

Going solar? Understanding how to calculate solar panel output is crucial for sizing your system correctly and estimating your savings. This guide covers everything from basic calculations to real-world factors affecting production.

Home battery storage system mounted on wall with solar panels
🌱Energy & Environment

Home Battery Storage: Complete Guide to Energy Independence

Home battery storage is revolutionizing how households manage energy. By storing excess solar power or cheap off-peak electricity, batteries provide backup power, reduce bills, and move us toward true energy independence. This comprehensive guide covers everything from capacity calculations to real-world savings.

Wind turbines at sunset generating clean renewable energy
🌱Energy & Environment

Wind Energy for Homes: Is a Small Wind Turbine Right for You?

Small wind turbines promise clean, renewable energy for homeowners. But unlike solar panels, which work almost everywhere, wind turbines require specific conditions to be economically viable. This honest guide explores when home wind power makes sense and when it does not.

Supporting converters

General-purpose unit converters you will use alongside the guides above — area for panel sizing, temperature for heat pumps, distance for EV range.

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ft² → m²

Square Feet to Square Meters

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m² → ft²

Square Meters to Square Feet

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°C → °F

Celsius to Fahrenheit

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m → ft

Meters to Feet

Dedicated calculators — in development

Purpose-built calculators for this pillar are being built. Until they ship, the guides above walk through the same math step by step.

Coming soon

Panel Output Estimator

Estimate annual kWh from panel Wp, tilt, azimuth and location.

Coming soon

Roof Sizing Calculator

Convert available roof area to a realistic system size in kWp.

Frequently asked questions

How many kWh does 1 kWp of solar produce per year?
Roughly 850–1,300 kWh per year in Northern Europe, 1,200–1,600 kWh in Central Europe, and 1,400–1,800 kWh in Southern Europe and the southern United States. Actual output depends on tilt, azimuth, shading, panel temperature and inverter efficiency. Panels lose 0.4–0.6% output per year over their 25-year warranted lifetime.
What is the difference between Wp and kWh?
Wp (watt-peak) is the panel’s power rating under standard test conditions — it says how fast the panel can generate energy at peak. kWh (kilowatt-hour) is the energy actually produced over time. A 400 Wp panel producing at peak for one hour yields 0.4 kWh. Real-world output over a year is what determines your electricity savings.
Is a home battery worth it with solar?
A battery increases self-consumption of your solar output from around 30% (without) to 60–80% (with), but adds significant cost and has its own degradation. Payback depends on the spread between the retail electricity price you avoid and the export tariff you would have received. It is most attractive where export tariffs are low and time-of-use pricing is high.
How much roof area do I need for 5 kWp?
Modern 400–450 Wp panels are about 1.9 m² each, so a 5 kWp system needs 12–13 panels or roughly 24 m² of usable, shade-free roof. South-facing pitched roofs are ideal; east–west splits still work but produce 10–15% less annually.
Does solar work in cloudy weather?
Yes, but at reduced output. Diffuse light on an overcast day typically produces 10–25% of clear-sky output. Panels are actually more efficient at lower temperatures, which is why cold sunny days can outperform hot summer days for the same irradiance level.
How long do solar panels last?
Tier-1 panels come with a 25-year performance warranty guaranteeing at least 80–85% of original output at year 25. Real-world data shows most quality panels still exceed 90% at year 25. Inverters typically need replacement once during the panel lifetime, usually at year 10–15.

Explore related topics

Energy decisions rarely stand alone — solar pairs with batteries and EVs, heat pumps pair with insulation and tariffs.

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Heat Pumps

Understand COP, SCOP and running cost — and see when a heat pump beats gas, oil or direct electric heating.

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Electric Vehicles

Charging cost, range and total-cost-of-ownership math — from home charger sizing to petrol comparison.

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Home Energy

Understand your electricity bill, size home storage, and cut standby consumption — the everyday side of the energy transition.

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Carbon Footprint

Translate kilowatt-hours, kilometres, kilograms and litres into CO₂ — with emission factors you can verify.