the house we moved into late last year came with what seems to be quite a good fujitsu heat pump in the lounge area. we had been using it in the evenings and mornings (turned off at night), but over the last month more throughout the day as well. our power usuage shot up by an extra 500 units for one month. the heat pump is not entirely to blame, we have oil heaters in 2 bedrooms - one used just for a few hours, the other on low from about 7pm for 13 hours.

when i spoke to powershop they said the heat pump should be on constantly as it will use less power. this seems strange to me but we tried it for a few days as well as the same for the 2 oil heaters, our power use increased by about 10 units per day. the frustrating thing is that we were using the fire to heat the house in the afternoon and evening (heat pump is turned off when the fire is going good), so not only are we paying more for power, but the cost of wood too! luckily we were just trialling for a few days, so now the oil heaters are back to the way they were before, the heatpump is on all through the night (it will be from the afternoon some days too) through to mid morning when the sun shows up! i will be checking the power use from doing this in a few hours (i'm trying to do it at same time of day).

my question is how often should our heat pump be on? is it best to have it on the whole night, or to set it to a timer to come on an hour before we get up? or is it the outside temperature that is making the whole unit work harder and therefore using more power?