Unit Converter & Energy Cost Calculators
Convert any unit below with full-precision, individually sourced factors — then use the energy calculators to turn kWh, litres and watts into what they actually cost you.
What are you trying to decide?
12 questions · Live calculatorsPick the question you actually have. Each one opens a calculator that states its result, what the result means, and which assumptions would change the answer.
Is solar worth it for my house?
Estimate system size, annual production, savings, simple payback and LCOE — with editable yield, system cost and electricity price.
Solar Payback CalculatorWill a heat pump beat my gas boiler?
Compare annual running cost against gas, oil, LPG or direct electric — using your SCOP, boiler efficiency and both energy prices.
Heat Pump Savings CalculatorWhat will my EV cost to charge?
Cost per session, per 100 km and per year from battery size, consumption, charging losses and your home/public tariff split.
EV Charging Cost CalculatorEV or petrol — which is cheaper for me?
The charging-cost calculator puts annual electricity cost side by side with a petrol or diesel car at your mileage, fuel price and consumption.
Compare against petrolWhat does this appliance cost to run?
Turn watts × hours × electricity price into a monthly and annual figure, appliance by appliance, and see which loads dominate your bill.
Home Energy AuditHow much am I wasting on standby power?
Annual cost and CO₂ of always-on routers, set-top boxes, chargers and idle appliances — usually 5–10% of a household bill.
Standby Power AuditWhat size home charger do I need?
Match 3.7 / 7.4 / 11 / 22 kW charge points to your battery, daily distance and overnight charging window.
Home Charger SizingWhat is my gas bill worth in kWh?
Convert m³, ft³ or therms of natural gas into kWh, cost and CO₂ with an editable calorific value — the input a heat-pump comparison needs.
Gas to kWh ConverterWhat is my household carbon footprint?
Home energy, driving, flights and diet totalled into annual tCO₂e, with the biggest reduction levers ranked.
Carbon Footprint CalculatorHow dirty is my electricity?
Convert kWh into CO₂ using published grid intensity factors, so savings can be expressed in emissions as well as money.
Electricity CO₂ CalculatorShould I fly or take the train?
Per-passenger emissions for the same journey by plane, train and car using published transport emission factors.
Flight vs Train CO₂Is a home battery worth considering?
No standalone battery calculator yet — this guide works through the self-consumption and tariff-spread arithmetic that decides it.
Home Battery Storage GuideOne place to answer every energy question that hits your household.
Every calculator links to the next. Solar payback references your electricity price, which flows into heat-pump savings, which feeds your carbon footprint. It's not a set of loose tools — it's an integrated energy planning platform.
Guided Decision Journeys
3 workflows · Step-by-stepAnswer one big question — should I install solar?, switch to a heat pump?, go electric? — through an ordered sequence of calculators and guides. Each step feeds the next, so you finish with a defensible decision, not a stack of loose numbers.
Journey
Should I install solar on my home?
A short path from an installer quote to a payback figure based on your own location, usage and prices.
- 1Note the system size
- 2Get location-specific generation
- 3Estimate self-consumption
- 4Calculate payback
- + 1 more steps
Journey
Should I replace my boiler with a heat pump?
A short path from last year's heating to a running-cost comparison and payback based on your own figures.
- 1Establish heat demand
- 2Find the right SCOP
- 3Compare running cost
- 4Add installed cost
Journey
Should my next car be electric?
A short path from a vehicle's consumption figure to charging cost, home charging need and a fuel-cost comparison using your own inputs.
- 1Find vehicle consumption
- 2Estimate charging cost
- 3Size home charging
- 4Compare energy cost
- + 1 more steps
Energy Categories
5 topic hubs · Deep guides + live calculatorsPurpose-built hubs covering the whole energy transition — from generation to consumption to emissions. Each hub bundles a flagship calculator, supporting tools and long-form guides.
Solar Energy
Plan, size and understand a solar installation — from panel output to payback and battery storage.
Heat Pumps
Understand COP, SCOP and running cost — and see when a heat pump beats gas, oil or direct electric heating.
Electric Vehicles
Charging cost, range and total-cost-of-ownership math — from home charger sizing to petrol comparison.
Home Energy
Understand your electricity bill, size home storage, and cut standby consumption — the everyday side of the energy transition.
Carbon Footprint
Translate kilowatt-hours, kilometres, kilograms and litres into CO₂ — with emission factors you can verify.
Flagship Energy Calculators
5 calculators · Payback, savings, CO₂Each calculator goes beyond simple arithmetic — reporting annual savings, CO₂ reduction, payback timeline and energy independence indicators so you can compare investments like an analyst, not a shopper.
Solar Energy
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 calculatorHeat Pumps
Heat Pump Savings Calculator
Compare annual running cost, payback and CO₂ reduction versus your current gas, oil, LPG or electric heating.
Open calculatorElectric Vehicles
EV Charging Cost Calculator
Cost per session, per 100 km, per year — plus savings vs petrol and CO₂ avoided, with editable home/public tariff split.
Open calculatorHome Energy
Home Energy Audit
Appliance-by-appliance annual kWh, running cost, CO₂ and share of bill. Surfaces standby losses and quick wins automatically.
Open calculatorCarbon Footprint
Carbon Footprint Calculator
Estimate CO₂e from home electricity, heating fuel, car fuel or EV charging and flights, with documented, editable emission factors.
Open calculatorFeatured Energy Guides
All Guides
How to Calculate Solar Panel Output
A solar panel's watt rating is not the energy it will produce. Annual output depends on the size of the system, how much sunlight reaches the panels at your site, how they face and are shaded, how hot they run, and the losses between the panels and your meter. This guide takes each factor in turn, shows the formulas with worked examples, and points to the official tools that estimate output for a specific roof. It covers generation only; what that energy is worth is a separate question, handled in the solar payback guide.
Heat Pump Efficiency Guide: Understanding COP and SCOP
A heat pump's efficiency is not one fixed number. COP describes performance at one set of test conditions; SCOP describes a whole heating season under a reference climate. Both change with the outdoor temperature, the water temperature the heating system needs, defrosting and how the system is controlled. This guide explains what each figure means, how ratings are produced, why a catalogue figure is not necessarily what your home will achieve, and how to turn a seasonal figure into electricity use. Running-cost and payback comparisons are covered in the heat pump savings guide.
How to Calculate EV Charging Time and Cost
This guide covers one charging session: how long it takes to add a given amount of energy, and what that session costs. The basic formula — energy ÷ power — is the ideal case. Real sessions can take longer because the car may accept less power than the charger offers, power falls as the battery fills, some energy is lost as heat, and battery temperature matters. Cost depends on the energy you are billed for and on how the tariff or network prices it. Monthly budgets, charger sizing and the comparison with a petrol car each have their own guide, linked where they come up.
How to Calculate Your Carbon Footprint
A carbon footprint is an estimate, not a measurement: activity data (kWh, litres, km, food, purchases) multiplied by emission factors and added up. What it includes — its boundary — and which factors it uses decide the total as much as your behaviour does, which is why two calculators can give different answers for the same person. This guide is the overall accounting framework: how to set the boundary, calculate each category, avoid double counting and read the total. Detailed guides for electricity, transport and food are linked from each category.
Home Battery Storage: How to Judge Whether One Fits Your Home
A home battery stores electricity to use later. Whether one suits a household depends on when you use electricity, when (or whether) you generate it, how your tariff and export payments work, and whether backup during a power cut matters to you. This guide explains the specifications that matter and a way to test the fit with your own numbers. It makes no general savings or payback claim: those depend entirely on your inputs. Solar economics and finding where your electricity goes each have their own guides.
How to Calculate CO₂ Emissions from Electricity
Emissions from electricity are one multiplication: kWh used × an emission factor. The multiplication is easy; the factor is the hard part. It depends on where the electricity is used, the year, whether it covers only generation or also grid losses and upstream fuel supply, whether it is a grid average or a supplier-specific figure, and sometimes on the hour. This guide explains each choice, with worked examples using published UK and US factors. It covers electricity only; the whole household footprint is a separate calculation.
Unit & Energy Converters
Full converter library111 converters across 10 categories — the mathematical layer under the calculators above. Every page shows the exact conversion factor, the formula, worked examples, a reference table and the reverse conversion.
Try “10 inches to cm”, “kWh to BTU” or “1500 W to kWh”.
Conversions used most in energy planning
kWh ↔ MJ
Exact 3.6 factor — energy reporting and datasheets
kWh ↔ BTU
Heating output on US and EU spec sheets
Therms ↔ kWh
Gas bill vs heat pump electricity cost
Watts ↔ Amps
Requires voltage — circuit and breaker sizing
mAh ↔ Wh
Requires cell voltage — airline battery limits
Ah ↔ Wh
Battery bank capacity at 12 V or 48 V
kW ↔ hp
EV motor output vs engine ratings
kWh ↔ MWh
Scaling from household to utility figures
Watts ↔ BTU/h
Heat pump and air conditioner capacity
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Kitchen Measurement Conversions
Essential cooking measurement conversions for recipes from around the world.
How to Convert Pounds to Kilograms
Convert weight between imperial and metric systems accurately.
Data Storage Units: MB, GB, TB Explained
Learn about digital storage from bytes to petabytes and how to convert between them.
Common Energy & Conversion Questions
Quick answers to the energy questions our calculators are built to settle, plus the conversions people look up most.
What SnapUnitConverter Is
SnapUnitConverter is built around one question: what should I actually do?The calculators here answer household energy decisions — whether rooftop solar pays back in eight years or fourteen, whether a heat pump beats your gas boiler at today's prices, what an EV really costs per 100 km, which appliances dominate your bill, and what all of it means in CO₂. Each one shows the result, explains what the result means, lists the assumptions behind it and flags which assumptions would change the conclusion.
Underneath the calculators sits a library of 111 unit converters covering length, weight, temperature, volume, area, speed, time, data, cooking, energy and electrical power. That library is the mathematical layer the decision tools stand on — and a reference in its own right. Every converter page states the exact conversion factor, shows the formula, works through examples, gives the reverse conversion and includes a reference table, so the answer is on the page whether or not you use the calculator.
Unit conversion, done properly
Each constant is stated at the precision of its own definition and cited individually, not covered by a blanket claim: the inch is 2.54 cm and the pound 0.45359237 kg by the 1959 International Yard and Pound Agreement, the British thermal unit is 1055.05585262 J per NIST SP 811, and mechanical horsepower (745.6999 W) is a convention rather than an SI definition. The methodology page lists every factor with its source and marks it exact, derived or conventional. The same constants drive the calculator, the formula text and the reference tables, so nothing on a page contradicts anything else on it. Values are rounded for display only; full precision is kept internally. Where US customary and imperial units share a name, we say which definition is used.
Energy calculators: the connected vertical
Most energy websites give you a single calculator and end the conversation there. Solar payback is calculated in isolation from your electricity price. Heat pump savings ignore what your solar array might contribute. EV charging cost forgets that a home battery could shift the load to your cheapest tariff. Here every calculator's output feeds forward as an input to the next: size a rooftop system with the Solar Payback Calculator, feed the generation into the Home Energy Audit, check electrification with the Heat Pump Savings Calculator, and close the loop with the Carbon Footprint Calculator.
Those calculators use the same physical models an engineer would use — panel degradation curves, SCOP-weighted seasonal efficiency, DEFRA transport emission factors, IEA grid intensity data — but behind interfaces designed for someone comparing installer quotes, not writing a thesis. If you want the assumption behind a number, click through: the formula is shown and the source is cited on our methodology page.