Free solar and energy calculators, made crystal clear.
Size solar panels, plan a battery, check payback and see what your appliances cost to run. Built for UK and European homes, with every formula shown.
Pick a question. Get a clear number.
Nine hubs built around how people in the UK and Europe actually plan solar, storage and energy use.
Plug-in & Balcony Solar
Plug-in solar kits sit on a balcony, wall or garden stand and feed power straight into a normal socket.
Solar Panel Sizing & Output
Start here if you are planning a rooftop system.
Solar Savings & Payback
Find out what solar is worth to you in money.
Battery & Storage
Size, charge and run batteries with confidence.
Electrical Calculators
Quick, accurate electrical conversions with European voltages as the default.
Energy & Running Costs
See what your appliances really cost to run, then find out how many solar panels it would take to power them.
Off-Grid & Van Solar
Plan solar for places the grid does not reach: cabins, campervans, boats and garden offices.
Solar System Design
Technical tools for checking a solar design: inverter size, string length, charge controller rating, cable cross section and voltage drop.
Solar Angle & Orientation
Find out how much your roof's tilt and direction matter.
What size home battery do you need?
Every calculator
Each one works instantly, explains its formula and cites its sources.
Latest guides
Plain-English answers, checked against official sources.
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Warm Home Discount 2026/27: Who Gets £150 and How
Who qualifies for the £150 Warm Home Discount in winter 2026/27, the key dates and how it is paid.
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Why Is My Electricity Bill So High? 10 Common Reasons
Estimated readings, standing charges, heaters, old appliances and other reasons bills rise, and how to check.
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How to Lower Your Gas Bill This Winter
Boiler settings, heating controls, draught-proofing and hot water changes that cut gas use most.
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How to Reduce Your Electricity Bill: 15 Proven Ways
The changes that cut electricity bills the most, with real costs at the October to December 2026 cap.
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How to Bleed a Radiator: A Step-by-Step Guide
Signs a radiator needs bleeding, what you need, the steps, and how to check boiler pressure afterwards.
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What Is a kWh? Kilowatt-Hours Explained With Real Examples
A kilowatt-hour in plain English, how to work one out from watts and hours, and what it costs today.
How we build every calculator
Primary sources
Prices, rules and standards come from Ofgem, gov.uk, the Energy Saving Trust and manufacturer data, checked on the day of writing.
Correct formulas
Every tool shows its working, so you can follow each step from your inputs to the answer.
Tested edge cases
Zero, empty and unrealistic inputs give a clear message instead of a wrong number.
Kept up to date
Defaults are reviewed when price caps, tariffs or standards change. See our editorial policy.
Quick answers
Are Solaxyra calculators free?
Yes. Every calculator is free to use, needs no sign-up and runs in your browser, so the numbers you enter are not sent to our server. We do not sell installer leads.
Where do the default prices and figures come from?
UK electricity defaults use the Ofgem price cap for 1 October to 31 December 2026. Solar yields, standards and safety rules come from primary sources such as government pages, Ofgem, the Energy Saving Trust and manufacturer datasheets, cited on each page.
Are the results accurate enough to buy equipment?
They are planning estimates. Use them to compare options and ask better questions, then get a site survey and quote from a certified installer. Electrical work must be done or checked by a qualified electrician.
Can I use plug-in solar in the UK?
Yes. Since 27 August 2026 certified plug-in solar kits with up to 800 W inverter output can be used in Great Britain. Our plug-in solar calculator estimates the yearly output and savings for your kit.