I would switch over to diesel instead of kerosense burns 30% hotter and therefore you should use less of it.
On all the time is a sure fire way of fuel running out quick! What I have done and I felt it was the only way to go was to install three 24 segment clock timers.
One for water, one for downstairs and one for upstairs. Now technically our boiler can burn a max of 3 litres per hour if on all the time which it never is. I have the heat on for 6 hours a day downstairs, 1.5 hours on the water and upstairs is on for 3 hours.
In theory the max I can burn in a day is 18 litres which means at this level 1000litres will last 8 weeks. Will it? Wait and see.
We put 2000 litres into the tank in January 11th and refilled it with a 1000 litres on November 12th so technically we got 10 months out of 2000 litres. However the heat was not used during the summer at all due to a tripped fuse from a pump in septic tank so it was off for a good 3 months. Now during the summer we would expect to use it only for an hour a day to heat the water.
I would say summer is June-September or maybe even May - any sun heats the house up very well.
The house is 4200 sq ft and I'd be happy if 2500-3000 litres was our average annual usage.
People in the country tend to say the use fcuk all oil which is either a lie or they don't count the 15-20 euro a week the throw on the fire etcetera!
I also feel that this year is a lot colder than this time last year imo!
I think there are other factors affecting consumption - heat loss from boiler to house - our boiler is in the garage which is 12-14m away - I assume it's insulated but not going to dig up the tarmac to check. I will be getting my boiler serviced before xmas.
I use the heat in an odd manner -
On a 24 hour cycle for downstairs it is as follows:
Total 6 hours and works out pretty well, if there was sunshine and higher temps this would be adjusted down to maybe 4 hours total.
Buy some cheap thermometers to see actual temp and humidity levels in the house as thermostats are imo not always accurate!