Our energy calculators are a deliberately small set of two tools for two big household questions: would solar panels make sense on my roof, and how much carbon does my lifestyle produce? They suit homeowners collecting installer quotes, renters curious about their impact, and students working on sustainability projects. Rather than a long list of niche tools, these two give you a solid starting figure you can take into a conversation with an installer or use to track changes over time.
Use the Solar Panel Calculator if you are weighing an investment in generation; use the CO2 Footprint Calculator if you want to see where your emissions come from. For the running-cost side of energy, the Electricity Cost Calculator and Fuel Cost Calculator in our Home & Auto section pair well with both.
How big a solar system does a home need? A rough rule is annual kWh ÷ (365 × local peak sun hours). A home using 10,000 kWh a year with 4.5 sun hours needs about 6.1 kW before losses, or roughly 15 panels of 400 W.
What usually dominates a household carbon footprint? Home heating and electricity, car travel and flights tend to be the largest items, with diet close behind. A single long-haul return flight can outweigh months of smaller savings.
Both energy calculators are free, run in your browser and need no sign-up. Results are estimates; a site survey gives the final word on solar.