- Joined
- 27 Jan 2008
- Messages
- 28,843
- Reaction score
- 3,527
- Location
- Llanfair Caereinion, Nr Welshpool
- Country
In the main, looking for if worth having a local DHW supply in the kitchen. To wash hands, likely electric is the best option, and to run a bath possibly oil may have the edge, but cost of electric is not easy to work out, as I am working with three prices, 8.625p/kWh off-peak, 12p/kWh loss of revenue when using solar, and 32.277p/kWh if my battery does not last until 00:30.
But more looking at losses if I have multi-hot water reservoirs, then increasing losses, even if reducing losses from pipe work, and also the cost of fitting a local DHW supply to start with. I don't think any of the hidden pipework is lagged, and I am paying to cool my living room with an AC, so to heat the room with hot pipes from boiler to cylinder is not a good idea.
AI tells me "In the UK, the average cost of heating oil (standard domestic kerosene) is currently around 9.5p to 10.5p per kWh." so if the boiler is 95% efficient and no losses in the pipe work, it will cost around the same, but it's not 95% efficient, so using oil is not a good option.
However, losses from cylinder to tap, hard to work out. Clearly depends on how much the pipe cools before used again. But working on a 5-year payback time, so one of these,
needs to save just 5p per day to break even, at the moment I spend approx 40p per day to heat my DHW using electric at peak rate, or 15p per day using solar, the under sink water heater will use some electric, and also encroach on cupboard space, and mean no hot water at the 4 other areas supplied with hot water.
But would mean in the kitchen hot water would be instant. If my wife decides she wants hot water at the other locations as well, then it becomes an expensive exercise with little benefit. And for 35p a day, seems simply not worth the effort.
So seems likely will continue to use centrally heated DHW.
My showers are both instant electric, I hardly ever have a bath, one has had an e-bike in it for 3 years.
But my realisation that electric is cheaper than oil, raises the question of what about instant gas or instant oil, i.e. the combi-boiler. In the main fitted to save space, and with the oil version, you still have a reservoir, but much smaller, with gas often an option eco off uses a reservoir, eco on does not.
So how much gas (in kWh so easy to compare) is used to wash one's hands with eco on? So turning on full, to get one litre of hot water, how much cold water has to be run off? I would say I need to run off around 1.5 litres first thing in the morning to get water warm enough to wash my hands, so to use 1 litre I heat 2.5 litres, since using electric, no loses else where.
Mothers old house, gas boiler in the kitchen, I would run off around 2.5 litres before I got hot water, but to heat the water running a boiler at 25 kW or more, not just 3 kW, so compared with an immersion heater, using a combi boiler is expensive. OK, may be worth it due to space gained, but it seems gas or oil DHW is more expensive to electric.
Am I missing something? I was told for years cheaper to heat DHW with gas, was this just a big con?
But more looking at losses if I have multi-hot water reservoirs, then increasing losses, even if reducing losses from pipe work, and also the cost of fitting a local DHW supply to start with. I don't think any of the hidden pipework is lagged, and I am paying to cool my living room with an AC, so to heat the room with hot pipes from boiler to cylinder is not a good idea.
AI tells me "In the UK, the average cost of heating oil (standard domestic kerosene) is currently around 9.5p to 10.5p per kWh." so if the boiler is 95% efficient and no losses in the pipe work, it will cost around the same, but it's not 95% efficient, so using oil is not a good option.
However, losses from cylinder to tap, hard to work out. Clearly depends on how much the pipe cools before used again. But working on a 5-year payback time, so one of these,
needs to save just 5p per day to break even, at the moment I spend approx 40p per day to heat my DHW using electric at peak rate, or 15p per day using solar, the under sink water heater will use some electric, and also encroach on cupboard space, and mean no hot water at the 4 other areas supplied with hot water.But would mean in the kitchen hot water would be instant. If my wife decides she wants hot water at the other locations as well, then it becomes an expensive exercise with little benefit. And for 35p a day, seems simply not worth the effort.
So seems likely will continue to use centrally heated DHW.
My showers are both instant electric, I hardly ever have a bath, one has had an e-bike in it for 3 years.
But my realisation that electric is cheaper than oil, raises the question of what about instant gas or instant oil, i.e. the combi-boiler. In the main fitted to save space, and with the oil version, you still have a reservoir, but much smaller, with gas often an option eco off uses a reservoir, eco on does not.
So how much gas (in kWh so easy to compare) is used to wash one's hands with eco on? So turning on full, to get one litre of hot water, how much cold water has to be run off? I would say I need to run off around 1.5 litres first thing in the morning to get water warm enough to wash my hands, so to use 1 litre I heat 2.5 litres, since using electric, no loses else where.
Mothers old house, gas boiler in the kitchen, I would run off around 2.5 litres before I got hot water, but to heat the water running a boiler at 25 kW or more, not just 3 kW, so compared with an immersion heater, using a combi boiler is expensive. OK, may be worth it due to space gained, but it seems gas or oil DHW is more expensive to electric.
Am I missing something? I was told for years cheaper to heat DHW with gas, was this just a big con?
