Energy Geeks - Cost of Living Question

Maybe, but..

£250 is ~ 1000kWh @25p or about 10 years of 8 hour days for a 60W laptop.

thanks @thisisnotaspoon. What are your workings?

The pack is £200 with a voucher and the price cap in October is going up to 51.4p (and then ~80 in Jan) so I want to recalculate.

Thx

If you add a monitor (2 monitors?) into the equation it might bring the payback timescale down to maybe 3 years, which isn't too bad, and it's a useful bit of kit to have anyway (for camping and suchlike), so even if the tariff saving only paid for half of it it'd maybe be worthwhile. Suspect there'd be some inefficiency to take into account in the charging & use of the powerbank mind.

Well if it's 80p then it's still ~3 years, if you have free electricity to charge it.

So assuming the overnight rate is half, that would make it about 6 years to repay itself at ~80p.

Now add inefficiency, charging/discharging is about 85%, then boosting that back upto 220V is about the same, so 70% (call it 2/3 for easy maths), then 6 years becomes 9 years. (Or 30 years when things return to normal).

I love the fact it has a 4 stroke engine. Can't be many battery packs with that feature.

It's not what the cost of the electricity increases to, it's the difference between your nighttime (charging) rate and your daytime (using) rate. I assume if the daytime rate goes to 51p and then 80p-ish then the nighttime rate will follow it as well, so the saving will be roughly the same.

Your nighttime electricity isn't free.

I have an EV tarrif that's locked at 7.5p from 12.30am to 4.30am nightly.

Thanks for your thoughts. For my knowledge, what maths are you using to work this out?

Good lock in! You’ll struggle to make back the cost of the unit… BUT… if we move from an energy cost to an energy rationing situation at any time in the next decade you’ll be the one laughing. Hang on, can you not use the battery in your EV to achieve this shifting of energy purchase/use time of day in a similar way?

Good lock in!

It's the Octopus Go tariff for EVs..I am considering going back on it so I can heat up my hot water overnight and I think an electric heater in the kitchen at 4.30am might keep it warm enough for breakfast at 7.

@molgrips that's the one! The real question behind this thread is 'how do I make use of those cheap kwh at night time?'. Guessing a storage heater would probably be the best solution...

Hang on, can you not use the battery in your EV to achieve this shifting of energy purchase/use time of day in a similar way?

I don't think you can *currently* (pun intented) - I think OVO energy were talking about doing that sort of thing a while back but it was for nissan leaf only and I think you needed a special 2 way charger.

Hang on, can you not use the battery in your EV to achieve this shifting of energy purchase/use time of day in a similar way?

There was talk of this but I don't think it ever happened. The main reason being that you would save less money than the cost of the reduction in battery life.

It will become viable when batteries get cheaper and electric gets more expensive.

You can in theory, it's called v2g (vehicle to grid) but it has to be supported by your car and your charger and you'd have to be billed through your provider. It's being worked on.

You could, if it's just for WFH, use v2l or vehicle to load, if you had a suitable car e.g. an Ioniq 5 and a long extension cable.

Edit: ah sorry, you are looking for vehicle to home which is the one being beta tested at the moment and only works with ChaDemo. V2G is for the benefit of the nation not directly your home.

The main reason being that you would save less money than the cost of the reduction in battery life.

I don't think it would touch the battery life if you're only using a small part of it, which you would.

But the above portable charger achieves the same aim.

<Blackmore>It will become viable when batteries get cheaper

😂😂😂

Re the power bank in the OP - you may be able to use it to power a heater if your demands aren't high. For me, I could use it to power a 1kW heater for about 3hrs, but of course I wouldn't need it on all the time, my room isn't particularly cold and only needs a bit of help in winter.

My overnight rate is currently 21p or so. Assuming I drained that whole power bank it'd be a third of a kWh at say 70% efficiency maybe half a kWh so it'd still save about 30p a day Vs using the electric heater directly from the mains. But the gas is about 18p/kWh anyway.

The question I have is how efficient is my gas central heating at delivering heat to one room? Lots of the heat is going to get lost in the pipes or be sent back to the boiler unless I heat rooms I'm not using.

The maths. A laptop pulling 60W for an hour uses 60Wh of electricity. If you use that for 8 hours, it will use 480Wh, close enough to 0.5 kWh for calculations as the kWh is the pricing unit of electricity.

Your saving is the difference between your daytime and night time electricity cost. On a per unit basis it'll be half a unit per day as per above x that number.

So if the <span style="text-decoration: underline;">difference</span> is approx 50p per unit it'll save you 25p a day. If the price goes to 80p and your nighttime stays at 7.5p it'll save you

(80-7.5) x 0.5 = 35p in round numbers.

Do it for 100 days and that is £35. A year is £127.

Heat "sent back to the boiler" just comes back out of the boiler again so isn't lost. Your only heat loss is in the pipes, which are probably buried in walls/floors so I suspect lose in the region of a few pence per day, all of which is mildly heating the house so it takes less energy to warm up later on. There will be some net loss, but not enough to be worth doing anything about

Heat “sent back to the boiler” just comes back out of the boiler again so isn’t lost.

Right but if the returning water is at 50C it'll absorb less heat on its way back through than if it's at 30C, because the temperature differential is less. The boiler efficiency is bound to drop when the return water temp is higher surely? These are the questions I have no answers to. That, and wether or not I have to heat the hallways to prevent the return temp being too high.

how do I make use of those cheap kwh at night time?

Better off trying to use it directly. What are your big electricity users, I doubt it's your WFH setup. Timer to run the dishwasher and washing machine at night, overnight slow cooker, etc

We run our dishwasher and washing machine at night using our cheap EV tariff. We don't risk the tube dryer, too much a fire risk.

Definitely fit a timer to your immersion heater if you are on Octopus Go. At that rate it's under half the price to heat with electricity and hot water is one of your biggest energy uses.

Good shout. Would immersion at 7.5p be cheaper than using the gas boiler tho?