Free for iPhone · UK

What would your bills be if you changed something?

Model a change, compare it against what you pay now, and see the difference in pounds before you commit to anything.

See what it does

No account
Stays on your iPhone
No subscription

A look inside

The sample three-bed semi on gas heating, with solar and better insulation tried against it.

Results for a three-bed semi: adding solar saves £353 a year, £1,371 against £1,724 now, with where the money goes — heating, hot water, appliances, lighting, cooking and standing charges. — The answer

The What If list: the home as it is at £1,724 a year, 4 kWp of solar at £1,371 net after £97 export income, and loft and cavity insulation at £1,634, each with its saving and carbon. — Try a change

Compare: the current setup against adding solar, where the difference comes from — £256 less electricity and £97 export income — and the What Ifs ranked for a budget. — Side by side

The home's details: a three-bed semi-detached house, electricity and gas, a combi gas boiler, no solar or battery yet, and cooking and appliances. — Your home

What you can model

Adding solar
Panel size, self-consumption, and what you’d actually export.
Adding a battery
Including time-shifting into an off-peak window.
Switching tariff
Your own rates, with exit fees and switch dates accounted for.
Riding the price cap
What the Ofgem cap would cost you now, and next quarter.
A heat pump
Heat demand from your actual home, with an efficiency you set, or a typical one.
An electric vehicle
Home and public charging, at the right rate for each.
Better insulation
What a filled cavity or a thicker loft would take off your heating.

Check it before you spend: What If Plus

An optional one-off purchase for the weeks before a big change. Everything above stays free, including typical costs, paybacks and price-cap reminders.

Installers' quotes, each with its own payback against the typical cost
Octopus Go, Cosy and Flux ready-made, at your region's rates
A one-page summary of a What If to share
Your home through a winter and a summer day, with a battery following the cheap windows
Tariffs with several cheap windows a day, and a reminder before your fix ends

Optional · one payment

£3.99

once · no subscription

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Bought through Apple and shared with your family through Family Sharing.

Your data stays on your phone

There is no account, no sign-in and no analytics. Everything you enter is stored on your device, and we have no way to read it. One optional feature sends a partial postcode to look up your energy region — never your full address, and you can skip it.

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