Sorry if I maybe using incorrect words, English is not my first language. I’m in France and there’s a big electric water boiler which provides all the hot water in our apartment. I have 2 questions regarding the energy consumption:
1. I suppose it consumes electricity initially to heat the water inside, but does it keep consuming to keep them warm?
2. Between 10pm – 6am, the electricity cost is lower in our plan. Does that mean it costs us less if we use the hot water(shower/dishes) between these times?
Cheers!
In: 1
>I suppose it consumes electricity initially to heat the water inside, but does it keep consuming to keep them warm?
Unless you have a magic box that keeps water hot forever, yes, it needs to keep using energy to keep it hot.
>Between 10pm – 6am, the electricity cost is lower in our plan. Does that mean it costs us less if we use the hot water(shower/dishes) between these times?
Yes, if you use water during that time, then the water that refills the tank will be cheaper to reheat during that time.
Heat will slowly leak out into the surrounding environment and the boiler’s thermostat will switch on every once in a while to maintain the set temperature. How much heat is lost depends on the insulation of the boiler.
You might save some money if you use water at night, because then the boiler will have to be on all the time until the water is heated up. You want to be using the water between 0:00 and 3:00 hours to give plenty of time for the boiler to reheat before the price increases again.
Look carefully at the electricity price to see if such micromanagement is worthwile. You might find that the “distribution fee” is the same at night, and not all nights are cheap on NordPool.
Your dishwasher probably heats its own water, rather than taking it from your boiler.
Your boiler will switch on and off to keep the water hot. Because hot water rises, it’ll always be hot near the top where your water leaves the boiler, even if it hasn’t turned on in a few hours. The difference will be in how soon you run out of hot water, not how hot the water is.
Many boiler designs just have temperature sensors at different heights. When the hot water at the top creeps up to a certain height, the boiler will turn on until it’s hot to a point further down in the tank again.
If your tank is big enough to not run out in hours of regular use, it would be beneficial to install a “smart” mechanism that delays the startup until electricity is cheaper. For example, if your family typically shower in the afternoon and early night, your boiler might have enough capacity to not need to re-heat until close to midnight, when electricity usually is cheaper.
Water heaters, at least in the US, are extremely well insulated. They do lose some heat to the environment, but it’s a lot less than you’d expect, especially if you also have your hot water pipes insulated. They only consume non-negligible amounts of electricity when they’re heating water and if you’re not actually using hot water, they’d probably only turn on the heating elements for less than half an hour per day under normal circumstances.
>Between 10pm – 6am, the electricity cost is lower in our plan. Does that mean it costs us less if we use the hot water(shower/dishes) between these times?
Yes. Though there’s some offset, so taking a long hot shower and ending at 6am won’t save much electricity compared to ending the shower at 530a.
You can have timer boxes installed to only allow the water heater to run during those hours and depending on the volume of your tank and your total daily usage you might not even notice. Though if you use more hot water in a day than your tank holds you will be in for a cold surprise.
We have a timer connected to our electric water heater so that we can set it to heat water only at certain times. It has worked fine that way. We have it on for an hour early morning and an hour early evening.
But I am in a sub-tropical climate, so the water also is relatively warm to start.
Short answer: yes.
Long answer: Water heaters are very clever.
Here, Mr. Connections explains it.
1. Yes, some heat leaks out though the insulation. It is quite little however, typical is around 400 kWh per year for a modern boiler. This heat also contributes to heating you house, so it is not entierly lost depending on climate and season.
2. It costs less if water is heated during this time. If the heater tank is large enought to last all day, you could potentially save a little bit of money by installing a timer and only let it heat between, for example, midnight and six o clock. You could turn up the water temperature if you frequently run of of hot water, although this will also increase the heat leakage a little bit.
A word of caution however, of you install a plug-in timer between the outlet and the boiler plug, make sure it is rated for the max power of the boiler and the make sure to touch it when the boiler is running to make sure the timer does not heat up. These cheap timers are often low quality and not made for high power during long periods, and have been known to overheat and cause fires. A better way would be to let an electrician install a timer, although that cost would likely offset your savings for many years ahead.
Objects do not consume electricity unless if they are actually doing work.
1. Your boiler keeps a certain amount of water at a high temperature. The boiler is isolated as best as possible to keep that water warm, but some heat will leak out. The boiler then replaces that heat by turning on for a bit to heat the water back up. The amount of energy lost depends on how good the isolation is.
2. yes, but it’s likely negligibly. I think it’s best to just use things as you need them.
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