Plug-in solar savings calculator
Last updated 26 August 2026
Work out roughly what a plug-in solar kit would save you a year, and how long it would take to pay for itself.
Most calculators you will find assume you use every unit the panel produces. Almost nobody does. Solar generates most in the middle of the day, which is exactly when a lot of households are out.
So this one assumes you use 55 per cent of what you generate and values the rest at nothing. That is deliberately cautious. If you are home during the day, run a heat pump, or time your washing and dishwasher for the afternoon, you will do better than the number below.
The single biggest factor is how much of the generation you use as it is made. If nobody is home during the day, a plug-in kit is a much weaker proposition than the headline numbers suggest.
What would you actually save?
Most solar calculators assume everything goes perfectly. This one starts from realistic settings and lets you make them better or worse. Exported energy earns nothing, so it counts for nothing here.
This is the number that decides everything. If nobody is home in the day it is nearer 30%. Working from home with a fridge, freezer and a hot water tank pushes it to 70% or more. Anything you do not use goes to the grid and earns nothing.
These numbers assume a kit sized like the one selected above. The kit page has the full specification and the register reference.
Estimates, not a promise. Real output depends on where the panel sits, what shades it, how clean the glass is and what the weather does. We would rather show you a cautious number now than a disappointing bill later.