Solar & Energy Calculators
Solar savings, EV charging, electricity bill & carbon footprint calculators.
What Are Solar & Energy Calculators?
Solar and energy calculators help homeowners, businesses, and sustainability professionals estimate the financial and environmental impact of renewable energy investments, understand their current energy consumption, and quantify their carbon footprint. As energy prices remain elevated and solar installation costs continue to fall, the economics of solar power are compelling for an increasing number of households and businesses.
Solar savings calculators estimate how much a solar panel system will save on electricity bills over its lifetime. The key inputs are system size (kWp), annual sunshine hours for the location, panel efficiency, self-consumption rate, export tariff or feed-in tariff rates, and current electricity cost. A well-sized residential solar system in the UK typically generates 850–950 kWh per kWp per year; in southern Europe or the US Southwest, this rises to 1,400–1,600 kWh per kWp.
Electricity bill calculators break down consumption by appliance, identify the biggest energy users in a household or business, and show the impact of efficiency improvements before committing to investment. Understanding that a storage heater, electric shower, or tumble dryer accounts for 30–40% of a household electricity bill is often the starting point for meaningful cost reduction.
EV charging cost calculators compare the cost of charging an electric vehicle at home versus public charging networks versus petrol/diesel running costs. Home overnight charging on a standard tariff typically costs 2–4p per mile in the UK; public rapid charging can cost 10–20p per mile — significantly reducing the economic advantage of EV ownership if relied upon heavily.
Carbon footprint calculators estimate CO₂-equivalent emissions from energy use, transport, diet, and purchases. The carbon intensity of electricity varies significantly by country and time of day — UK grid electricity averaged approximately 200 gCO₂/kWh in 2023 but can fall to under 50g/kWh during periods of high renewable generation. Understanding your emissions profile is the first step toward meaningful reduction.
All Solar & Energy Calculators (6)
Solar Battery Calculator
Calculate the battery storage size needed to power your home from solar energy.
Solar Savings Calculator
Calculate how much you can save on electricity bills by installing solar panels.
EV Charging Cost Calculator
Calculate the cost to charge an electric vehicle at home or at public charging stations.
Electricity Bill Calculator
Calculate your electricity bill from appliance usage, kWh consumption, and utility rates.
Carbon Footprint Calculator
Calculate your personal or household carbon footprint from energy, transport, food, and lifestyle.
Generator Size Calculator
Calculate the generator size (kW/kVA) needed to power your home or business.
Solar & Energy Calculator Guides
Solar Panel Savings
Annual Generation = System Size (kWp) × Peak Sun Hours per Day × 365 × System Efficiency Factor (typically 0.8 for losses). For a 4 kWp system in the UK at 2.7 peak sun hours/day: 4 × 2.7 × 365 × 0.8 ≈ 3,153 kWh/year. At 28p/kWh electricity cost and 50% self-consumption: annual saving = 3,153 × 0.5 × 0.28 = £441 from avoided purchases, plus export income on the remaining 50%.
Solar payback period = Total System Cost ÷ Annual Net Saving. A 4 kWp system costing £7,000 saving £700/year (including export income) has a payback of 10 years. Solar panels typically come with 25-year performance warranties — the post-payback years represent pure financial return. Battery storage extends self-consumption from ~30% to ~60–70% of generation but adds cost and typically extends payback by 4–8 years.
Energy Consumption
Appliance energy consumption: kWh = Power (kW) × Hours of Use. An electric shower at 9 kW used for 8 minutes daily = 9 × (8/60) = 1.2 kWh/day = 438 kWh/year. At 28p/kWh, that is £122.64/year for showers alone. A tumble dryer at 2.5 kW running 3 hours/week = 2.5 × 3 × 52 = 390 kWh/year = £109/year. Identifying high-consumption appliances is the highest-return energy saving exercise.
Energy Performance Certificates (EPCs) rate a property\'s energy efficiency from A (most efficient) to G (least efficient). Improving from an E to a C rating typically saves £600–£900/year on energy bills. Our electricity bill calculator models the saving from specific improvements — insulation, LED lighting, smart controls, heat pumps — to help prioritise investment.
EV & Carbon Footprint
EV running cost per mile: Cost = (Miles per kWh efficiency ÷ 1) × Electricity Rate. A car averaging 4 miles/kWh charged at 7p/kWh (overnight Economy 7): 7 ÷ 4 = 1.75p/mile. The equivalent petrol car at 40 mpg and 150p/litre: 150 ÷ 40 × 1.609 (km/mile) ÷ 100 × 100 = approximately 6p/mile — making home-charged EVs roughly 3–4 times cheaper to run per mile than petrol vehicles.
Carbon footprint from electricity: CO₂ = kWh × Grid Carbon Intensity (gCO₂/kWh). UK average 2023: ~200 gCO₂/kWh. Using a 100 kWh appliance: 100 × 200 = 20,000 gCO₂ = 20 kg CO₂. Solar electricity has a lifecycle carbon intensity of approximately 20–50 gCO₂/kWh — 4–10× lower than grid average — making it one of the most effective tools for reducing a household\'s energy-related carbon emissions.
Top Solar & Energy Calculators
Solar Savings Calculator
Estimate solar panel savings, payback period, and lifetime return for any system size and location.
Solar Panel Calculator
Calculate how many solar panels you need and the expected annual generation for your roof.
Electricity Bill Calculator
Break down your electricity bill by appliance and identify the highest-cost energy users.
EV Charging Cost Calculator
Compare the cost of home vs public EV charging and calculate savings vs a petrol or diesel car.
Carbon Footprint Calculator
Estimate your annual CO₂ emissions from energy, transport, and household consumption.
Key Formulas & References
Solar Annual Generation
kWp × Peak Sun Hours/Day × 365 × 0.8
0.8 = typical system performance ratio (losses from heat, wiring, inverter)
Appliance Energy Cost
Power (kW) × Hours Used × Unit Rate (£/kWh)
Annual cost = daily cost × 365
EV Cost per Mile
Electricity Rate ÷ Efficiency (miles/kWh)
Compare to petrol: fuel price ÷ (MPG × 0.2199) gives pence/mile
Carbon from Electricity
kWh × Grid Intensity (gCO₂/kWh) ÷ 1,000
UK average ~200 gCO₂/kWh; result in kg CO₂
Frequently Asked Questions About Solar & Energy Calculators
A typical UK home uses 3,500–4,000 kWh of electricity per year. A 4 kWp solar system (approximately 10–12 panels) generates around 3,000–3,500 kWh/year in the UK, covering most of annual consumption. For homes with EVs or heat pumps, a larger 6–10 kWp system is more appropriate. Our solar panel calculator sizes the system based on your actual consumption and roof orientation.
Solar payback period = Total Installation Cost ÷ Annual Net Saving. Annual net saving includes electricity bill reduction (from self-consumed solar generation) plus export income (for surplus sent to the grid). In the UK, typical payback periods for residential solar are 8–12 years without battery storage. With a battery, payback extends to 12–16 years but energy independence increases significantly.
Energy used (kWh) = Power rating (kW) × Hours of use. Cost = kWh × Electricity unit rate. For example, a 2.5 kW tumble dryer running 3 hours per week at 28p/kWh costs 2.5 × 3 × 0.28 = £2.10/week or approximately £109/year. Our electricity bill calculator lets you input all your appliances to see total consumption and identify the biggest cost drivers.
Yes, significantly cheaper when charged at home. Home overnight charging typically costs 1.5–4p per mile vs 6–10p per mile for petrol at current prices. However, relying on public rapid chargers (30–80p/kWh) narrows or eliminates the cost advantage. Maximising home charging and avoiding peak-rate public chargers is the key to realising EV cost savings.
Carbon intensity is the mass of CO₂ emitted per unit of electricity generated, measured in gCO₂/kWh. It varies by country (France ~85 g/kWh due to nuclear; Germany ~385 g/kWh due to coal; UK average ~200 g/kWh in 2023) and by time of day (lower when wind/solar output is high). Solar and wind generation have lifecycle emissions of 10–50 gCO₂/kWh, substantially below grid average in most countries.
Battery storage increases self-consumption from around 30% to 60–70% of solar generation. In the UK, a typical 10 kWh battery costs £4,000–£7,000 installed and saves an additional £150–£250/year. Payback periods of 15–20 years make standalone battery economics marginal at current prices — but batteries improve grid independence and provide backup during outages. They are most economic when paired with time-of-use tariffs.
BrainyCalculators Editorial Team
Our Solar & Energy calculators are researched, built, and reviewed by the BrainyCalculators editorial team using industry-standard formulas and validated against authoritative references. Results are updated whenever underlying standards, rates, or guidelines change. All calculators are free, require no account, and run entirely in your browser.