Could someone give me a guide to calculating cost of appliances please?

MoneyMon555

I don't have an energy meter  and would like to know how much a few appliances might use in electric per hour.

If I have the kW rating of the appliance uses and I know how much my electric unit rate is, how do I calculate how much that appliance would cost to run?

Thanks

grumbler

kW rating is meaningless in this respect.

To get some indication check specifications, kWh/year for a fridge, kWh/wash etc.

How come you don't have a meter?

victor2

Running an appliance that uses 1KW for 1 hour will use 1kWh of energy, so it will cost whatever your rate per kWh is for electricity.

However, few appliances use what they are rated at all the time they are on. Fridges are an obvious one - it may use say 200W when the compressor is running, but next to nothing when not, and the compressor may run for 20 minutes at 20 minute intervals. These are just made up ratings to illustrate the example.

As @grumbler says, kWh/year for a fridge, or kWh for the wash cycle you choose for a washing machine are much more meaningful. Plug-in monitors are cheap (less than £20) and can be used to tell you what any appliance (so long as it plugs in) has used over a period of time.

MoneyMon555

Apologies for confusion, I meant  I don't have a Smart meter, which would make it simple.

I can look at the electric meter if I had the appliance on and all other things being equal work it out, but if I am looking to buy something and work out before hand how much it would cost how would I do that?

One of the things I was thinking of was heating just one room with a small heater, but in the past I always thought of them as hugely expensive and inefficient. But I dont know if that's just a conception I have? I wanted to do it a bit more scientifically. ie have gas heating on for hour and turn down other radiator valves and then work out how much that costs. Then compare that against various appliances that might keep the same room warm for the same duration of time using electric and compare before buying. 

As far as I can see, fan heaters etc don't give the detailed info as you mention above?

victor2

MoneyMon555 said:

Apologies for confusion, I meant  I don't have a Smart meter, which would make it simple.

I can look at the electric meter if I had the appliance on and all other things being equal work it out, but if I am looking to buy something and work out before hand how much it would cost how would I do that?

One of the things I was thinking of was heating just one room with a small heater, but in the past I always thought of them as hugely expensive and inefficient. But I dont know if that's just a conception I have? I wanted to do it a bit more scientifically. ie have gas heating on for hour and turn down other radiator valves and then work out how much that costs. Then compare that against various appliances that might keep the same room warm for the same duration of time using electric and compare before buying. 

As far as I can see, fan heaters etc don't give the detailed info as you mention above?

Electric heating will still cost more than gas, but central heating is designed to heat an entire dwelling, albeit with individual controls on radiators.

Electric heaters with thermostat controls will only use their rated power until the thermostat switches it off.

A simple fan heater with no thermostat rated at 1kW will use 1kWh every hour it is running. So if your rate is 40p/kWh, it will cost you 40p for every hour it is on. But, one with a thermostat control will only run at its rated power as long as it is heating up. When it switches off depends on so many variables - the temperature the room starts at, how quickly the room loses heat, how big the room is, the temperature you choose, etc.

For example, if I was WFH in one small room used as an office, I could switch off the central heating and use a small fan heater to keep comfortable. That would cost less than keeping the central heating on, even if it meant the rest of the house was chilly.

Look at your historic gas usage for last winter (the kWh you were billed for) and get an idea of the daily/weekly cost at today's rates.

Compare it to the summer usage to get a feel for what your central heating cost. Hot water costs a bit more in the winter too, but it will give you an idea.

That difference in money is roughly what you would be looking to replace by electric heating. Divide the daily cost by the hourly electricity rate and you'll get the number of kWh you could use for electric heating per day.

All "back of a fag packet" numbers, but will give you a feel for it.

grumbler

MoneyMon555 said:

Apologies for confusion, I meant  I don't have a Smart meter, which would make it simple.

I can look at the electric meter if I had the appliance on and all other things being equal work it out, but if I am looking to buy something and work out before hand how much it would cost how would I do that?

See my post in this thread - Vampire devices

One of the things I was thinking of was heating just one room with a small heater, but in the past I always thought of them as hugely expensive and inefficient. But I dont know if that's just a conception I have? I wanted to do it a bit more scientifically. ie have gas heating on for hour and turn down other radiator valves and then work out how much that costs. Then compare that against various appliances that might keep the same room warm for the same duration of time using electric and compare before buying. 
As far as I can see, fan heaters etc don't give the detailed info as you mention above?

All electric heaters are equally efficient - 100%, but the electricity is much more expensive than gas. However, with an electric heater you can heat a small area/volume, that is more difficult to do with gas.

macman

MoneyMon555 said:

Apologies for confusion, I meant  I don't have a Smart meter, which would make it simple.

I can look at the electric meter if I had the appliance on and all other things being equal work it out, but if I am looking to buy something and work out before hand how much it would cost how would I do that?

One of the things I was thinking of was heating just one room with a small heater, but in the past I always thought of them as hugely expensive and inefficient. But I dont know if that's just a conception I have? I wanted to do it a bit more scientifically. ie have gas heating on for hour and turn down other radiator valves and then work out how much that costs. Then compare that against various appliances that might keep the same room warm for the same duration of time using electric and compare before buying. 

As far as I can see, fan heaters etc don't give the detailed info as you mention above?

Every single electrical appliance sold in the UK has a rating plate giving it's consumption in Watts.

FreeBear

MoneyMon555 said: One of the things I was thinking of was heating just one room with a small heater, but in the past I always thought of them as hugely expensive and inefficient. But I dont know if that's just a conception I have? I wanted to do it a bit more scientifically. ie have gas heating on for hour and turn down other radiator valves and then work out how much that costs. Then compare that against various appliances that might keep the same room warm for the same duration of time using electric and compare before buying.

I have a "smart" home automation system that records the temperatures in each room of the house (and outside). It also controls the heating system along with various "smart" switches.

As an experiment last winter, I put a fan heater in a room that had recently had internal wall insulation fitted. Using the HA system, ran the heater for a few hours, and with the outside temperature around 0°C, I was using approximately 0.15KWh of electricity to maintain the room at 20°C. A human body will generate 80-120W of heat, so once occupied, the room would require even less energy to heat.

If you are wanting to conduct any experiment yourself, you really need some way of measuring and recording the data of the device & space under test. So a energy monitoring plug (e.g. Tapo P110), and a couple of thermometers (one inside, one outside) would be the minimum requirement. A smart gas/electricity meter just won't have the granularity of readings to give any meaningful results.

Don't forget, the outside temperature can make a huge difference to how much energy is needed to heat a room. So you should be factoring it in to any calculations/comparisons you make.

grumbler

macman said:

MoneyMon555 said:

Apologies for confusion, I meant  I don't have a Smart meter, which would make it simple.

I can look at the electric meter if I had the appliance on and all other things being equal work it out, but if I am looking to buy something and work out before hand how much it would cost how would I do that?

One of the things I was thinking of was heating just one room with a small heater, but in the past I always thought of them as hugely expensive and inefficient. But I dont know if that's just a conception I have? I wanted to do it a bit more scientifically. ie have gas heating on for hour and turn down other radiator valves and then work out how much that costs. Then compare that against various appliances that might keep the same room warm for the same duration of time using electric and compare before buying. 

As far as I can see, fan heaters etc don't give the detailed info as you mention above?

Every single electrical appliance sold in the UK has a rating plate giving it's consumption in Watts.

The OP wanted kWh.

For a heater without a thermostat you just multiply kW by the time of actual use to get kWh.

With a thermostat it's more complicated and will depend on many factors, ultimately on the time the heater  actually heats, not just is switched on.

MoneyMon555

Thanks all. I suppose a very accurate comparison might be hard, but was just looking to see if I could work out if an electric heater for one room would be cheaper (and I see with the variables of a thermostat on it , it's not straightforward).

I could always get something from Amazon, read the power consumption plate on it as mentioned above and then even run it for a set time and see if it is comfortable in the 1 room, and then run the CH for same length of time with TRV set at a certain point.

Although, maybe the best bet is just to set CH to a temp comfortable in 1 room with other rad valves turned off. I would guess that is the lowest cost I can arrive at?

Thanks for input all, food for thought

MoneyMon555

MoneyMon555 said:

Thanks all. I suppose a very accurate comparison might be hard, but was just looking to see if I could work out if an electric heater for one room would be cheaper (and I see with the variables of a thermostat on it , it's not straightforward).

I could always get something from Amazon, read the power consumption plate on it as mentioned above and then even run it for a set time and see if it is comfortable in the 1 room, and then run the CH for same length of time with TRV set at a certain point.

Although, maybe the best bet is just to set CH to a temp comfortable in 1 room with other rad valves turned off. I would guess that is the lowest cost I can arrive at?

Thanks for input all, food for thought

Thanks for that link Grumbler