Lay My Hat

Hi, is it better to have a timer on the electric water heater and have it heated twice a day for certain periods of time, or keep on all time? Anyone noticed differences to electricity bills?

If you leave the heater on 24/7 you are paying to replace the heat lost through less-than-perfect insulation and the hot water lost through consumption. Assuming you store heated water from one session to another (despite consumption) there will be little to choose between your two options.

However, if you have carefully timed sessions and use all/most of your (morning heated) water and leave the tank cold/cooler all day and the same at night, you will have lower overall heat losses and lower overall cost by using the timer.

If you have a bi-horária tariff heating using off-peak electricity will be much cheaper, so restricting heating to the relevant periods will be desirable, if you can store sufficient volume of water to meet your needs.

Regardless, get the best insulated water tank you can find. During the winter your heat loss will help to heat your property but in summer it will add to your discomfort.

Not in Portugal, but the same principles apply elsewhere. Our water is full of calcium and other minerals which fur up hot water elements at an alarming rate. We changed from 24/7 to timed several years ago and estimate that we get an extra 12 months of life for an electric element in consequence.

Our mains water seems to be pre-softened, so scale isn't really a problem. I believe keeping heated water below approx 60C is the best way of reducing scale formation and has the added benefit of greatly reducing the rate of heat loss compared to hotter water. If you always add colder water, your hot water is too hot.

If and when the tank needs replacing consider installing an "on demand" system.

Thanks to all the advice, much appreciated. Just thinking that the electricity will be turned off when the property is vacant, so could be weeks or few months without use (winter). So how to ensure the timer works correctly once power restored by cleaners the day before guests arrive?

If you're using a timer it will need some form of battery backup to allow for random power cuts, accidental unplugging etc in normal use. But then you have the problem of ensuring that the battery is replaced and, if necessary, the timer re-programmed.

Adding the need to last months between checks or recharges makes your task even harder.

The cost of keeping a clock/timer powered 24/7/52 is tiny compared to the cost of heating water if there's nobody at home. Maybe instead of turning off the power to the whole property you just need to ensure that the water heater is turned off, so the timer stays alive?

The problem doesn't arise for us here in France as our electricity is on day and night tarif, and automatically switches to the cheaper night tarif at 11pm. The water storage heater (capacity enough for a day) is only connected to the night tarif. If hot water does run out during the day, you can switch it on to heat the water and then it automatically goes back to the night tarif. We disconnect the electricity when no one is there so we use this facility when we expect an arrival during the day.