Economy 7, Immersion Water Heater & Storage Heaters. How to save money as a first-time tenant?

IbnBattutah

Hi all,

Just started my first tenancy in a top-floor, all-electric two bedroom apartment with an immersion water heater and electric storage heaters. The whole setup seems alien to me, and unfortunately most of the literature is vague. So hoping someone can hold my hand and explain how things work so I can avoid being spanked by these ever-increasing energy prices.

Usage

So I'm renting alone and also work from home. I would say my hot water demands are low (5 min morning shower & wash dishes in the evening). As for heating, I'm not cold blooded and tend to wrap up well in the winter months. 17c room temp is tolerable. 

Storage heater and Immersion tank

The apartment has 6 storage heaters in total, ranging from 2kw-3kw in output power. Albeit they are all ancient

Re the immersion heater, its an unvented 210L Megaflow Heatrae Sadia system with two switches attached to it by wires. The flip switch that connects to the lower thermostat is for off-peak, and the other switch connects to the upper thermostat and that is for the peak tariff. To the side of the system sits a Horstmann E7BX Boost Control box, which is identical to this (see photo). There is only one dial on this, going from 0 hours to 2 hours. 

Tariff

Octopus currently provide to the property and the last tenant was absurdly paying £270 p/m for 12,000 kWh annual usage. Despite the projected usage being around the 5000 kWh mark for a 'medium user'.

 The current Economy 7 tariff charges a standard charge of 48.34p, with a day rate of 29.06p kWh and night rate of 21.54p kWh.

Questions....

1) Storage heater - Am I best not using these at all and employing a oil filled radiator in whichever room i'm occupying at the time? 

2) Are there any ramifications to not using the built-in storage heaters in the winter? 

3) Based on my usage, would it be a waste of electricity to leave off-peak switch on all night? 

4) Based on my usage, would I be better off switching on the 'peak' switch when I wake up so I can have a shower in the morning and again in the evening to wash up? 

5) If so, how long would I need to keep the switch on so the I can shower (for 5 mins) and wash up (for 5-10 mins or so) with warm water? 

6) What does the boost control box do? 

7) By using the immersion heater sparingly, am I at risk of freezing pipes in the winter? 

8) By only turning the immersion heater on x minutes before I need hot water, am I at risk of legionella by not warming the whole tank up? 

10) Does the cold water come through the tank before it hits the taps or is it a fresh supply directly from the external pipes? 

Thanks in advance!

QrizB

Welcome to the forum.

IbnBattutah said:

Just started my first tenancy in a top-floor, all-electric two bedroom apartment with an immersion water heater and electric storage heaters. The whole setup seems alien to me, and unfortunately most of the literature is vague.

This is quite a conventional arrangement for an all-electric flat. There are hundreds of thousands of other flats with similar heating systems, and quite a few houses too.

Octopus currently provide to the property and the last tenant was absurdly paying £270 p/m for 12,000 kWh annual usage. Despite the projected usage being around the 5000 kWh mark for a 'medium user'. The current Economy 7 tariff charges a standard charge of 48.34p, with a day rate of 29.06p kWh and night rate of 21.54p kWh.

12000kWh/yr isn't outrageous, and I think 5000kWh/yr is quite low for a two-bed apartment that's large enough to have six storage heaters. You should have been provided an Energy Performance Certificate (EPC) as part of your tenancy agreement. What does that have to say regarding annual energy use?
12000kWh/yr on that tariff will cost between £2800-£3600/yr, depending on how much is day-rate and how much is night-rate. If the tariff is variable/flexible, you can expect it to rise significantly in October.

5000kWh/yr will cost £1250-£1630/yr.

1) Storage heater - Am I best not using these at all and employing a oil filled radiator in whichever room i'm occupying at the time? 

2) Are there any ramifications to not using the built-in storage heaters in the winter? 

3) Based on my usage, would it be a waste of electricity to leave off-peak switch on all night? 

4) Based on my usage, would I be better off switching on the 'peak' switch when I wake up so I can have a shower in the morning and again in the evening to wash up? 

5) If so, how long would I need to keep the switch on so the I can shower (for 5 mins) and wash up (for 5-10 mins or so) with warm water? 

6) What does the boost control box do? 

7) By using the immersion heater sparingly, am I at risk of freezing pipes in the winter? 

8) By only turning the immersion heater on x minutes before I need hot water, am I at risk of legionella by not warming the whole tank up? 

10) Does the cold water come through the tank before it hits the taps or is it a fresh supply directly from the external pipes?

1. Possible but unlikely. More likely, you'll either be cold or you'll spend more; worst case you'll spend more and you'll still be cold. If you're likely to spend most of your time in one or two rooms, I'd be tempted to keep those storage heaters switched on and switch the others off.

2. No, other than being cold and/or spending more on heat, provided you don't go away for a week during a cold snap and everything freezes.

3 & 4. As you're living alone, 210 litres of hot water is more than you're likely to need. You might want to get a competent person to swap the wiring on the immersion heaters over, so you can heat the top one on cheap rate electricity for your shower, then boil a kettle for the washing-up.

5. At least 30 minutes.

6. The knob controls how long the top immersion heater runs for.

7. No, so long as your flat stays above freezing.

8. No, it's an unvented system.

9. Missing.

10. Cold should be straight from the rising main, since your hot tank is unvented.

Swipe

Another option for your hot water is to put the boost on for 30 mins for your shower before the peak rate window ends. This is assuming your shower is fed by the hot water tank and you don't have an electric power shower that separately heats cold water from the mains. If the latter, then forget the immersion heater unless you want a bath and just shower at off peak times. Also as mentioned, buy a small bowl and boil a kettle for washing up. 

I have 8 storage heaters and if all are used, my annual consumption is close to 20,000 kWh so just keep that in mind on your current standard tariff rates or you will get an extremely expensive surprise.

[Deleted User]

Hi,

here's a wee VIDEO, might help.

EssexHebridean

The first thing here is to start learning about the set up you have - so look up the makes and models of your storage heaters and research. 

Economy 7 is the most beneficial the more electric you can use overnight - so have a think about which routine things you can do either while you sleep, or at this time of year, very first thing in the morning. (A shower before the rate changes from night to day for example will be a lot cheaper than one after the meter has said "click")

Learn your E7 timings - at the moment ours (in East Anglia) are 01.11 > 08.11 and once it gets cold get into the habit of regular checking of the weather forecast a few days ahead so you can decide how to change heater settings.

We also live in a 2 bed flat  with Immersion/storage heaters and generally we run things like this:
Our shower is a straightforward electric mains fed so does not use water from the tank - hence trying to use it on cheap rate where possible.
Storage heaters - hallway and front room are on (only in winter obviously), others are off - the hallway one also provides heat to the spare room and bathroom to prevent damp and mean neither are too chilly when needed. Our bedroom doesn't need heat as we both prefer a cooler room anyway - we use additional layers of fleece blankets in particular cold weather. All internal doors to those rooms left open to allow airflow and some warmth to penetrate through.  
The immersion - we leave ours on timed unless we're away from home - that then provides sufficient water for face washing, for MrEH's shaving, and for washing up as and when needed. We found that just heating it from cold when required worked out a lot more expensive - ours is a well insulated one so once it's hot unless a lot of water is used from it through a day it doesn't take much time/energy to heat it subsequent days.

On older storage heaters you will likely find that setting the output to "closed" will give you the best result - they lose a fair bit of heat through leakage anyway through the day, and that gives the best chance of still having some heat available in the evenings. 

I will say that the deal you're currently on appear to be extremely high - I assume this is a fix you have signed up to? If not then you might look at switching about as right now pretty much every other supplier should give you a better deal on the cap! 

QrizB

EssexHebridean said:

I will say that the deal you're currently on appear to be extremely high - I assume this is a fix you have signed up to?

It looks to me like the SVT rates for Flexible Octopus in Yorkshire?

https://octoenergy-production-media.s3.amazonaws.com/documents/Flexible_Octopus_April_2022__PDF_VAT.pdf

EssexHebridean

QrizB said:

EssexHebridean said:

I will say that the deal you're currently on appear to be extremely high - I assume this is a fix you have signed up to?

It looks to me like the SVT rates for Flexible Octopus in Yorkshire?

https://octoenergy-production-media.s3.amazonaws.com/documents/Flexible_Octopus_April_2022__PDF_VAT.pdf

Thanks Qriz - I must have misread something somewhere along the line as yes, it does doesn't it - will amend my post!