GenRun: Generator RuntimeGenRun: Generator Runtime
How many hours of petrol are left in the tank, and what time you will need to top it up.
Download on the App Store
Screenshots
Features
Hours that move with the load
How long the tank lasts is never a fixed figure. Enter the tank size and rated output of your genset, add up what you have plugged in, and GenRun estimates the hours remaining as the demand changes.
The time you will need to top up
As well as hours remaining, GenRun gives you a clock time for the next fill, which is far easier to plan around than a bare countdown.
Live Activity on the Lock Screen
The countdown sits on your Lock Screen and warns you while there is still fuel in the tank, so the engine stops when you decide rather than at three in the morning.
Consumption modelled properly
Dividing the rated runtime by load percentage flatters a lightly loaded machine, because friction, cooling and windage carry on regardless. GenRun uses a no-load loss plus a load-proportional term, which is how a small engine really drinks.
Learns the habits of your own genset
Record a few genuine fill-ups and the app calculates the burn rate of your particular machine. A well-used site genset is not the one described in the handbook.
Petrol, diesel and LPG
Litres or gallons, as you prefer. Bottled gas is tracked by weight in kilograms, the way it is actually sold. A home screen widget is included. iPhone only.
How long will the tank last? That is never a fixed number. It depends on how hard the generator is working, and that changes the moment somebody plugs in a kettle.
GenRun takes your generator's tank size and rated output, adds up what you are actually running, and estimates how many hours the fuel in the tank is good for — plus the clock time you will need to top it up.
WHY MOST ANSWERS ARE WRONG
The usual method is to take the rated runtime and divide by load. At a quarter load that arithmetic says you have plenty. In reality an engine burns a large share of its fuel simply spinning: friction, cooling and windage do not go away when the load does. On a typical small genset the proportional method can overstate light-load runtime by well over 200% — think 38 hours quoted when the honest figure is closer to 12.
GenRun models consumption as a no-load loss plus a load-proportional term, which is how fuel actually behaves.
A RANGE, NOT A FALSE PRECISION
Your biggest source of error is not the maths, it is not knowing exactly what your appliances draw. So GenRun shows a range rather than a single confident number. A wide range tells you to go and check something; a narrow one tells you the plan is sound.
ON THE LOCK SCREEN
A Live Activity keeps the countdown on your Lock Screen and warns you while there is still fuel in the tank, so the generator stops when you decide rather than at three in the morning.
IT LEARNS YOUR MACHINE
Log three or more real refuels and GenRun works out your machine's own burn rate. Engines drift from the manufacturer's figure as they age, and a well-used site genset is not the same machine it was when new.
FUELS AND UNITS
Petrol, diesel and LPG. Bottled gas is tracked by weight in kilograms, the way it is actually sold, rather than being fudged into litres.
CARBON MONOXIDE
The app opens with a full-screen warning about carbon monoxide the first time you run it, and it cannot be skipped. Generators are for outdoors only — never in a garage, porch, conservatory or caravan awning, even with the door open.
PRACTICAL NOTES
Everything the app produces is an estimate to help you plan a refuel, not a promise. Check the tank yourself. Shut the engine down and let it cool before refuelling, and follow the manufacturer's instructions for your machine.
PRIVACY AND PRICE
No sensors, no accounts, no network connection. Everything stays on your iPhone. One payment, no subscription, no in-app purchases, no adverts.
Useful when a winter storm takes out the power, on a caravan or narrowboat, at a remote site, on a market stall, or anywhere a small engine is standing between you and the dark.