The size of the generator will of course depend on ones needs, but I generally suggest the following, for a modest size and modestly equipped home I suggest about 4KW. this allows 1 KW in total for the large numbers of lamps and low consumption appliances found in most modern homes, and also allows 3 KW for just one heavy loading appliance such as a kettle, a space heater, , a washing machine, a tumble dryer, or a table top electric cooker. But only one such appliance at a time.

For a larger or more generously equipped home, I would select a 7KW generator. This allows 1.5 KW for more lamps and for some duplication of small appliances. And also 5.5KW for use of any two large loading appliances. From a 7 KW generator a 3KW immersion heater can be used, preferably via a load sensing relay that only enables the water heater when other loads are limited.

Seems sensible, but what fuel will the genset use? Diesel now, but in 10 years? I shall get my state pension in two and a bit weeks, but I hope to draw it for more than a decade.

Its a good question. Once traditional cars fade out, it may be that the supplies of fuel do too. Propane stays in tanks longer  than petrol or diesel without separating or freezing, some sort of biogas would be ideal, but in the longer term it is not clear what will be available. The ability to light a fire is likely to be useful too.

Mike

For a 4KW or 7 KW petrol or diesel fuel may be selected.

Diesel fuel is safer and cheaper, and almost any volume may be stored.

Petrol is more expensive, and more dangerous, only 30 litres may be stored lawfully A petrol generator is cheaper to buy and easier to start. A diesel generator needs electric starting in most cases which adds to the expense.

If you drive a diesel or petrol car, then that suggests that the same fuel be used for the generator. Fuel stocks may be rotated via the regularly used vehicle.

For a 4KW or 7 KW petrol or diesel fuel may be selected.

Diesel fuel is safer and cheaper, and almost any volume may be stored.

Petrol is more expensive, and more dangerous, only 30 litres may be stored lawfully A petrol generator is cheaper to buy and easier to start. A diesel generator needs electric starting in most cases which adds to the expense.

If you drive a diesel or petrol car, then that suggests that the same fuel be used for the generator. Fuel stocks may be rotated via the regularly used vehicle.

As a 'rule-off-thumb' a gallon (4.5 litres to the yung uns!) of diesel is worth about 25kWh out the back of a genset. It was legal, in years gone by, to run gensets on red diesel but thats no longer allowed.