Charging up your home?

So I’ve been thinking of ways of cutting our energy bills now that there’s not really any cheap tarrifs.

I’m now paying basically 20p a kWh (19.73p kWh Electric / 3.84p kWh Gas) which I think is pretty average now with EON (Sainsbury’s Energy)

Other than the big five British Gas, EON, EDF, OVO, Scottish Power theres basically only Octopus providing any alternative. All the others look to be on the rocks if they will survive this winter.

The tariffs I can see that provides cheaper electric are the following that offer an Economy 7 style peak and off-peak rates, aimed at EV drivers.

British Gas Electric Drivers (12-5am @ 12.990p, peak 39.183p)

EDF GoElectric

E.ON Next Drive (12-4am @4p)

OVO Drive EV

Scottish Power Electric vehicle

Octopus Energy Go

Does anyone use one of these?

Anyway that got me thinking, wouldn’t it be possible to charge your home up within the off-peak hours, and use the stored energy within the other hours of the day.

It turns out that you can with my limited research so far.

Basically you need to work out how much on average your house uses daily and then buy a battery system of that size.

It comes with a control box to sit after your meter and before your consumer box which basically is set to top up at the off-peak times, and then only take from the grid at peak if its emptied the battery storage.

These appear to be a few thousand to install which sounds a lot but being charged 5p vs 20p is probably only going to take 4 years to pay for itself in how much it’s saving over 48 months.

I can only see the price per kWh going up from here. My only doubts is whether the energy providers will always have the off-peak rates. Maybe in five years time when a lot more EV peeps are using the grid out of hours theres less surplus. Or the energy companies just get greedy and work together to get everyone to pay the same regardless of time of day.

My other thoughts are they tend to have a 10 year life span, so you’ll be winning for 6 years in savings but they potentially need to swap out the battery module (but the control box should be fine)

And the other thing is battery storage is rapidly improving, especially with solid-state lithium and testing out other non-lithium solutions so within the 10 year lifespan becomes outdated tech. There’s a possibility the provider goes bust and you end up struggling for parts.

What’s your thoughts?

Here’s two I’ve been interested in:


Doesn’t @Lewis_P do something like this?

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I’m currently on :octopus: Go, with 15.78p per kWh from 04:30 to 00:30 and 5p per kWh from 00:30 to 04:30
Car charging and dishwasher running between 00:30 and 04:30 every morning.

If you qualify - take a look at the new Intelligent Octopus tariff. Interesting blend of Half-Hourly ‘slots’, with cheap rate from 23:30-05:30 guaranteed. They basically can ‘move’ your car charging times to the cheapest HH slots. I have to wait until Ohme support and an Android app are available :disappointed:

Home batteries - and there are a lot of options here (PV/no-PV, V2H to be considered) - include the Tesla PowerWall, Givenergy and PrimeHybrid solutions. I don’t have battery storage yet. Cost is a huge factor and I’ve concentrated on keeping the ‘running’ costs down rather than investing in additional hardware for the long-term.

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Looks to be Tesla only atm :face_with_raised_eyebrow:

The GivEnergy caught my eye with its Giv-Bat 8.2 Unlimited (100% depth of discharge).

I can’t see the lower ones would be applicable for me as I would really need ~10 I think with my calculations so far.

This “sonnenBatterie 10” also looked ace but I haven’t enquired on price. 11 kWh with a 4.6 kW charge/discharge rate.

I think I need to get the calculator out and work out potential savings on the :octopus: Go tariff based on being able to charge back up in those four hours at 5p.

Then see how much it would cost to buy and install.

It seems far more cost effective than Solar Panels just to grab at the cheaper rate and use within the other 20hrs of the day.

Can’t say I ve looked into it much, but, strikes me there must already be quite a few second hand EV batteries floating around. I quickly found this company selling them BMW i3 120Ah Battery module - Tested Used EV Modules | Battery | EV Project .

No idea if they work out better but maybe worth a look?


Just watched this YouTube and it’s exactly my thinking. He’s using that Giv-Bat 8.2 with Octopus Go. He talks about a similar tariff of 5p and 15.4p similar to yours, but mentions its now higher peak. It was back in Oct too before everything went nuts.

Octopus Go here, over my 24 hours of usage from the last 6 days, my daily average p/kWh is 15-16p. I’m saving about 40-50%.

I’m averaging usage of between 4-7kWh/day depending on if I run the Dishwasher/Washing Machine - neither of these are able to be scheduled, so I run them when I want to, so slightly more expensive than if I used my 5p window.

For me, next time my washing machine/dishwasher decide to have an issue, I’ll be replacing them with ones that can be scheduled to save even more. Probably more cost effective in the short term, vs battery solution etc.

Personally, I think if I was 100% sure I’d stay somewhere 10years, I’d go Solar/Battery + off-peak topup, as a setup and run the house as close to self-sufficient electric as possible.

Edit to add:
Octopus Go:

  • 25.01p standing charge
  • 00:30-04:30: 5p
  • 04:30-00:30: 16.67p
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Current peak is 24p :sweat:

I would really need to make sure that the battery can provide the other 20hrs

This is my other concern, our current house isnt our planned forever home. It looks like the modules can be moved and restored back to “normal” but that’s an added cost.

I would like Solar too but on our next home. The battery storage seems to be more cost-effective before adding Solar.

Would love to be 100% off grid but would take a lot of solar panels to achieve or a smaller house.

Just out of curiosity…
If you start your current dishwasher/washing machine and then switch off, or unplug, at the plug - it’ll obviously stop. But if you leave it a minute or two and then switch on at the plug, or plug back in - does it then continue from where it was and complete the cycle? If it does, there’s a very cheap way to schedule the appliance(s).

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I don’t believe they’ll drop the off peak price reductions.

Electricity can’t be easily stored on a massive scale, and energy sources that can’t be quickly powered up and down will be running during the night as well as wind power.

I did see an interesting suggestion somehere that your EV can be the big battery storage for your house, it charges up during the night and can power your home when it’s plugged in, although that will come at a cost of battery degradation impacting range of your car.


You can’t normally move stuff like this out of a house you are selling, it belongs to the new owners. You’d have to get it clarified through the solicitors, but could be a problem if they then ask for a reduction in the sale price


Indeed, it would either need to be in the contract that it wasn’t included or removed before sale.

Possibly might add some value sold installed and running but would be harder to find a potential buyer that wants it like that.

Description says it runs on a home battery, wuh? :man_shrugging: is that a thing :tipping_hand_man: :thinking: sounds weird, experimental and potentially costly to maintain, next. :neutral_face:

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Indeed, they might have very different electricity usage too meaning the battery wouldn’t work as well for them.

Here’s my situation:

  • I’m on octopus go 5p (00:30 - 04:30), 14p (04:30 - 00:30)
  • I have an EV (renault zoe ZE50)
  • I have 2.2kw solar array (costing £3,950 in 2019)
  • I’ve been weighing up the pros and cons of battery storage for about 2 years.

Our two-person semi-detached household uses between 5kWh per day and 10kWh per day, and an additional 30kWh once or twice a week depending on how often I need to charge (see graph below). I have a dumb EV charger installed so I can’t take advantage of the solar and charge directly from that, so I charge during the off-peak time overnight instead;

Our 2.2kw solar array generates between 7kWh and 15kWh per day in the summer and between 0kWh and 5kWh in the winter;

The solar generation during the day doesn’t typically align with our usage:


We are on a Feed in tariff so we get a rebate for every kWh that our solar array generates:

Once you factor in the Feed in tariff rebate, our total utility bills hover around £600 per year:


Since our bills are so low, the potential savings from getting home battery storage are also pretty low. Personally I think I’m going to end up waiting on vehicle to grid (V2G) technology. I can’t really justify spending £5k on a 5kWh battery system, when I’m already paying ~£14k over a 4 year PCP for the 50kWh battery sat on my driveway.

Things that might change my mind include;

  • shifting to electricity for our heating (either through electric underfloor heating, heat pump, electric shower, etc). If my electricity usage is significantly higher, then home battery storage starts to become more financially viable.
  • if my mileage per week significantly rises then a home battery plus a smart charger would help offset the additional charge costs.
  • if the cost of home battery storage drops significantly.

At the moment, I think the most likely scenario for me will be that my next EV in 3 years time will have V2G.


The only thing I’ve noted is something like the Ioniq 5 which has V2L the output is just enough to run a handful of electrical items directly into the single 3-pin socket on the adapter. It’s good if you want to go away camping away from a camp site and want to take a mini-fridge and microwave into the middle of nowhere.

With IONIQ 5’s Vehicle-to-Load technology (V2L) you can power any device or charge electrical equipment up to 3.6 kW with the on-board 220V plug.

It’s not quite the same deal as what the F-150 Lightning (if we ever see that in the UK)

Ability to off-board 9.6 kW of peak energy

Would be nice to just get a Powerwall :sweat_smile:

13.5 kWh capacity is probably what I need looking at averages.

I’ve just watched this on it

Based on the May date on the upload that was the 2016 model before the Nov facelift.

Screenshot 2021-12-07 at 16.09.31

I think this is the only thing stopping me is that the UK prices are taking the piss.

Screenshot 2021-12-07 at 16.11.45

compared to

£2,673.60 incl. VAT

Granted thats not 13.5kWh but even with getting all the parts and labour it can’t be more than £4kish

Could it save almost grand a year :thinking:

Off-peak 15p cheaper than my current two year fixed, however in two years it’ll prob be 30p kWh

5000 * 0.05 = £250
5000 * 0.20 = £1000

£750 year saving based on 5000

5000 * 0.25 = £1250
5000 * 0.30 = £1500

5000/365 = 13.7

6000 * 0.05 = £300
6000 * 0.20 = £1200

= £900

6000/365 = 16.5 avg :frowning:

So yeah a potential break even at roughly 5 years on a non-tesla setup.

With the Powerwall it would mean a decade min break even

With potential battery life at 10 years I’m :expressionless:

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So my electric usage is only around 2750kWh per year but if I could capture all of my annual solar (2400kWh) and use it, I could offset the vast majority of my usage and be left with needing to pay for just 350kWh (at 0.05p that’s just £17.50).

On the surface that sounds great, but its still only a saving of about £400 per year, so the payback on even a cheap battery would still be around a decade. And a cheap battery wouldn’t have enough capacity to capture a full summers day’s worth of solar (15kWh).

I do really want to get a home battery, but I can’t make the sums work. I think the only way I could make it make sense would be to vastly increase my electricity usage. Which might happen as I try to use less gas for stuff.

I’m not too worried about battery life. Even if it drops to 80% capacity after 10 years it would still be helping.


I don’t know how your dishwasher works but I found a way around mine not having a timer.

It turns that if the power is cut to the dishwasher then when the power comes back it continues the cycle without needing any human input.

So I fitted a smart plug which is on a timer for my off peak hours, then just before bed (or work depending on the night of the week!) I get Alexa to turn the plug on, press the start button, get Alexa to turn the plug back off and hey presto in the middle of the night it does it’s thing.

Nothing more annoying though than going to it the next morning and realise I didn’t push the door all the way shut!

One of the benefits of working nights is that I do all my washing and tumble drying in the early hours so it’s both cheap and better for the environment (as electricity in the early hours is generally much greener)

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Oh you beat me to it!

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What do you use to plot all those graphs? :heart_eyes:

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