Water heating, immersion or CH?

Cantisque

Hello,

Where I currently live, all heating is electric.

There are two ways to heat water (I just discovered today!).

1) Through the 12-13KW central heating boiler which then pumps hot water into the tank (I think, I definitely hear the pump going).
2) Immersion heater, which is 3KW and seems to be directly inside the tank at the bottom.

The CH method allows me to control the time and day it comes on and I've been micro-managing it to come on for 30 minutes every 2 days (I don't use a lot of water, and it usually stays hot for those full two days).

The immersion method I have to manually turn on and off, but it seems to automatically switch itself off as well once it reaches a certain temperature which is nice, so long as I remember to turn it off again at the wall when it does (and as I only just found out I have this thing, I am unsure exactly how long it will take to fully heat). Downside to that is I can't set it on a timer to run at 4AM like I can with the other one, so I'd need to make sure I remember to run it the night before so I don't end up with a cold shower!

I was told the immersion heater would be the better one to use in terms of cost and efficiency because less energy is wasted pumping hot water through the (admittedly short) stretch of pipes. Would that be a fair assumption? Would it be a big enough difference to be worth ditching the timer controls?

(Sorry if poorly explained, if it's not obvious I am not well versed in these things)

Many thanks!

Chrysalis

For me gas water heating is not only more efficient but actually gives me a better supply of hot water.

I havent used immersion since about a decade ago, when I tried to use it, heated water would go cold when bath only half full and even then it was hot/warm rather than actual hot.  With gas boiler it stays hot filling the entire bath.  It also heats much quicker on gas, on immersion it needed about 2 hours, with gas about 40 minutes in summer and about 60-90 in winter.

For things like washing dishes, kettle is more efficient than both.

However a family member insists for them their immersion is more efficient than their gas water heating so they do it that way.

TheElectricCow

The immersion will technically be more efficient as less energy will be wasted compared to the boiler, but unless you have an incredibly cheap electric tariff (i.e. close to the price of gas) using the boiler will be the more cost effective solution overall due to the difference in unit rates of gas & electric.

Generally speaking gas is much cheaper than electric per unit, so if your gas system was running at just 80% efficiency it would still cost less for the same amount of hot water than heating with the immersion.

Cantisque

As mentioned, it's all electric. The property does not have gas.

Chrysalis

Well with the timer system, you open yourself up to the possibility of heating water when you dont need it, you may have hot water all day, but do you need it all day?

If you looking for a more scientific answer, I cant help you as I dont have any data, but if you dont get any useful responses, if you have a smart meter you can compare data on that from using one or the other.

Cantisque

The meter is too far away for the unit to transmit to/from unless I go downstairs, but I do get daily readings sent to the E.ON app so that could still be a good way of figuring it out, I could try running both methods for a week or two and see which one works out the best.

Chrysalis

Cantisque said:

The meter is too far away for the unit to transmit to/from unless I go downstairs, but I do get daily readings sent to the E.ON app so that could still be a good way of figuring it out, I could try running both methods for a week or two and see which one works out the best.

If you only have daily readings from E.ON, try and get the bright app, it should give you 30 minute breakdowns which will help you.

Lorian

If it's an electric CH boiler then theoretically the immersion heater would be more efficient for the reasons stated, but both will be expensive. 

Make sure the tank and all the pipes around it are lagged as much as possible to reduce the heatvlisses. Post some pictures of the tank if you want some feedback on the insulation position.

littleboo

As already said, the immersion heater is in principle more efficient, but the lack of control may mean it's on more than necessary, topping up when you don't need it to.
You could consider an immersion heater timer, DIY if you are competent or a sparky if not. That gives the best of both worlds.

QrizB

Cantisque said:

Where I currently live, all heating is electric.

I don't think you've mentioned, but do you have a single-rate electricity tariff or a multi-rate one (where the cost of electricity depends on the time of day)?

Gerry1

Do you really have an electric boiler supplying wet radiators?  Nothing is more expensive !

If you're renting, it might be worth considering a move.