Size it by the surge, not the running load
A fridge that draws 200 W asks for up to 600 W the instant it starts. Same for a pump, a compressor or an air conditioner: anything with a motor.
The correct sum is: add the running load of everything you will connect, then add the largest single starting surge (not all of them, because they do not start together). Add 20% so it never runs at the limit. Our generator calculator does it with the usual appliances preloaded.
Do not run it at 20%
A petrol generator wants to sit between 40 and 80% of its rating. Heavily underloaded it fouls up, carbons and burns more fuel. Buying twice what you need is not safer: it is worse.
Start things in the right order
Generator first with no load, let it settle. Then connect loads from largest to smallest, waiting a few seconds between each. That way no surge stacks on another.
The maintenance that really matters
- Oil: first change very early, at 20 to 25 hours. After that, every 100 hours or once a year.
- Air filter: blow out or replace depending on dust. On site, far more often.
- Spark plug: check it once a year. It costs little and prevents impossible starts.
- Fuel: this is what kills most generators. Petrol degrades in weeks and leaves varnish in the carburettor.
If you are storing it
Drain the carburettor or use a fuel stabiliser. Run it once a month for ten minutes with some load. A standby generator that will not start on the day of the blackout is worthless, and it is almost always stale fuel.
Safety, plainly
Never run it indoors, in a closed garage or next to an open window: carbon monoxide has no smell and it kills. And do not connect it to your home panel without a transfer switch fitted by an electrician: you can electrocute whoever is repairing the line.
