Independent UK home energy tools
Find out what actually pays back
Solar, batteries and EV charging are sold on headline savings. We model the whole picture instead: how much you really use, what degrades, what you export, and how long it takes to break even.
Free, no signup, no email. Takes about two minutes.
The shape matters more than the crossing point, especially around a battery replacement.
What we actually model
Most calculators quietly guess on your behalf. These are the parts we refuse to skip, because they are usually where the optimism hides.
Battery degradation and replacement
A battery does not hold its day-one capacity for twenty years. Treating it as a fixed box overstates the return, so we degrade capacity over time and account for replacement.
Self-consumption, not just generation
Power you use as it is generated offsets the import rate. Power you export earns the export rate, which is lower. The split matters more than most people expect, and it turns on when you are actually home.
Import and export tariffs separately
They are different rates and they do not move together. Collapsing them into one average number quietly changes the answer.
The full curve, year by year
Not a single payback year. The shape tells you more than the crossing point, particularly around the point a battery may need replacing.
Today's money, not tomorrow's
Every figure is in today's prices. We do not escalate future savings by an assumed energy price rise, which is how a twenty-five year total gets inflated into a number that looks far better than it is. Savings in year twenty are shown in the same pounds as year one.
The tools
One is finished. The others are being built, and we would rather say so than pad the list.
- Available
Solar and battery ROI
Model payback for panels and storage on your home, year by year.
Open the calculator - Planned
EV charging costs
What charging at home actually costs against public rapid charging.
- Planned
Heat pump running costs
Running costs against a gas boiler at current tariffs.
Latest posts
Working through the questions in public, with the numbers shown.
- 6 min
Are solar panels worth it in Scotland?
Less sunlight than the south of England, but not as much less as people assume, and installation prices that are genuinely lower per kilowatt.
- 5 min
Solar panel payback period: how to calculate it properly
Why the headline figure on a quote is usually optimistic, and the arithmetic that corrects it without pretending to more precision than exists.
- 5 min
Why solar panels are not worth it: five honest cases
North roofs, empty houses, short stays, cheap tariffs and expensive finance. The situations where the sums genuinely do not work.
Common questions
Is the calculator free, and do I need an account?
It is free and there is no signup. You do not need to give an email address, and we do not ask for your name or postcode.
How accurate is the payback figure?
It is an estimate, and it is most useful as a comparison tool. It works from your annual usage and an occupancy pattern rather than your actual half-hourly consumption, and it does not know about shading or your roof pitch. Changing one input at a time to see what moves the result tells you more than the headline number does.
Does it account for the battery wearing out?
Yes. Battery capacity is degraded over the life of the projection and replacement is accounted for. A projection that models a battery as a fixed-capacity box for twenty years will overstate the return.
Why do your numbers differ from an installer's quote?
Usually because of assumptions about self-consumption and export rates, which is where most of the disagreement between any two calculators lives. An installer also knows your specific roof and prices, which we do not.
Do you sell solar panels or pass on my details?
No. We do not install anything and there is no lead form, so there are no details to pass on. The calculator runs and gives you the answer.