Moving from a property with combi boiler to electric immersion

Reed_Richards

And again, how is the house heated?  Even with triple glazing and lots of insulation, you are likely to spend more on heating the house than you will on heating the hot water.  In fact you will have an Energy Performance Certificate that will give you estimates of how much energy your house heating and your hot water heating will consume.  Also, unless your house is all-electric, it's quite surprising that you only have an immersion heater for your hot water.  Are you sure that is correct?  

Alnat1

My simple non-expert thoughts - Heating a certain amount of water from one temperature to another will take the same kW of energy whatever fuel. A boiler is less efficient than direct electric heating so will use slightly more.

We use our gas boiler to heat our 160l tank (modern, well insulated, feels only slightly warm to touch) for 40 minutes each morning. Tank temp is set to 50C as is boiler. This gives us enough hot water for 2 morning showers, hubby's shave and a bit left over for cleaning etc. If we need more we can boil a kettle, although not had to yet.

This uses under 3kWh of gas a day, might have to put up boiler temp a bit in winter when incoming water will be colder, so perhaps 4kWh. We rarely have baths but can put it on boost manually for 15 minutes extra and get enough for a medium depth bath.

Hope this helps you see that hot water tanks aren't so bad if used efficiently.

throughtheblue

lohr500 said:

Related to dunstonh's question, how is the house heated? Is that all electric as well?
You mention that it has no mains gas, but does it have oil or LPG?
If it is electric heating, what type? Night storage heaters on an Economy 7 type tariff or conventional electric heaters running on a single rate tariff?

Not to add to your worries, but if the house is heated by electricity and you intend to keep it warm this winter then the water heating cost could well be a small percentage of your total consumption.

There will be a log burner installed, but currently it's electric panel heaters.

I wasn't as concerned about this, as the property is triple glazed with 400mm loft insulation and 5 star rated wall insulation. I stayed early March and had the heater on for less than an hour and then had to open a window when sleeping due to the heat.

I'm hoping this doesn't become another huge expense.

throughtheblue

Reed_Richards said:

And again, how is the house heated?  Even with triple glazing and lots of insulation, you are likely to spend more on heating the house than you will on heating the hot water.  In fact you will have an Energy Performance Certificate that will give you estimates of how much energy your house heating and your hot water heating will consume.  Also, unless your house is all-electric, it's quite surprising that you only have an immersion heater for your hot water.  Are you sure that is correct?  

Electric panel heaters, and a log burner. Only electric immersion, for certain.

The EPC is suggesting £1000 per year on heating, and £300 on heating water.

I currently live in a victorian flat, with single glazed windows, little to no insulation, and exposed wood flooring. My partner and I have gone through winters where we may put the heating on 1-2 hours each day. In the new property, I can't imagine having the heating on a great deal, maybe an hour after work in the evening.

matelodave

TBH an electic shower won't really save you much compared with using hot water from the tank. They both use full price electricity. Quite frequently electric showers can be a bit pathetic in the winter unless you get a powerful one because the incoming water is a lot colder than in the summer

What will save you money is taking shorter showers and fewer of them and making sure that you've got a low flow/eco shower head. You could also reduce the tank temperature to around 55 degrees. Add some insulation to the pipework around the tank to reduce any conduction losses

We get away with heating our 200l tank to 45 degrees, every other day in the summer and that gives us enough water for two to four showers (although the last one is a bit cool, but acceptable). We have a 6lpm shower head and can shower etc in around 2-3 minutes.

The other way to save hot water is to avoid short draw downs. Don't use hot water for rinsing stuff including your hands and dont let hot water run down the sink. Letting the tap run until the water is hot, not only wastes several litres down the drain but leaves the same amount of valuable hot water sitting in the pipes to get cold.

Just to allay the fears of the Legionella brigade, the tank is heated to 60 degrees once a week which means our hot water lasts even longer.

Reed_Richards

throughtheblue said:

Electric panel heaters, and a log burner. Only electric immersion, for certain.

The EPC is suggesting £1000 per year on heating, and £300 on heating water.

Are those figures based on the (about) 34p per kWh we will be paying for electricity from October?  If so, £300 for hot water is less than £1 a day, which surely should allay your fears of massive expense.    

QrizB

Does your EPC also give an annual energy demand in kWh?

throughtheblue

Reed_Richards said:

throughtheblue said:

Electric panel heaters, and a log burner. Only electric immersion, for certain.

The EPC is suggesting £1000 per year on heating, and £300 on heating water.

Are those figures based on the (about) 34p per kWh we will be paying for electricity from October?  If so, £300 for hot water is less than £1 a day, which surely should allay your fears of massive expense.    

I can't find a KWH/unit price figure in the EPC report, but it was only done last month, so it must be fairly accurate. I would guess the figures are based on the current rate their which is 26.51p. So possibly an increase of £75 a year to add.

throughtheblue

QrizB said:

Does your EPC also give an annual energy demand in kWh?

Current Flat, electricity with Combi boiler for water and heat = 302 kWh/m2/year

New House, just electric = 452 kWh/m2/year

But we can significantly reduce the main expense of heating by using the log burner. We'd plan on buying enough fuel for 5/6 months of the year.

Reed_Richards

throughtheblue said:

I can't find a KWH/unit price figure in the EPC report, but it was only done last month, 

In my case (EPC September 2020) the kWh per year figures are right at the end in a section called 

Heating use in this property