Can you run an all electric house for free?

Solarchaser

A little over a year ago I was paying £110 / month for electricity, which doesn't sound alot for a 3 bed semi family of 5, but i had already invested in quite a few ways to cut the annual cost. 
I had a large solar array already installed and a large battery bank taking charge from the solar to reduce annual costs as much as possible.

No heat pump as the wife says NO.

I was already using batteries on Intelligent octopus to charge at 7p overnight in the winter, and heating water tanks overnight to produce heating and hot water.
Already had electric car(s)

I had already improved insulation in the loft and below the house.

My thought was to reduce import as much as possible, so as to lower costs, however after reviewing costs, it looked like I was going to have to increase my monthly payment as my annual import was up to £1470 and 16000Kwh

I read on here that Octopus would pay 15p for every Kwh you exported, and that set my mind running.
I fudged some calculations and done some man maths and decided to give it a go.
I'm on a 2014 FIT rate, so I had to give up my deemed 50% export payment (but not the generation payment) which would have gotten me around £106 this year

So instead of charging from the sun and reducing export, i instead went to never charging from the sun and actively trying to export all the solar i generated.

I bought a total of 29053Kwh.
Of that 4812Kwh was used to charge two electric cars, the rest was house consumption. 

My bill for the year was £137 including the car charging.
Without the car charging it would have been -£200 (but id have had to pay petrol or diesel obviously)


I've done this by exporting all of my excess solar power instead of using it to charge batteries as i had done for the previous 6 years,  and then charging batteries overnight and setting them to export between 4pm and 8pm each evening.
I export at this time for 2 reasons which are kind of the same reason.
1. The grid is dirtiest at this time due to everyone making dinners.
2. We make dinners between these times.

This export has offset the cost of the import.
Total export was 13256Kwh at 15p/Kwh

I continued to pay the £110 /month to octopus and so i now have £1500+ sitting in the account, some of that is from the free hours charging that octopus does now and then and recommending friends, so I didnt think the money in account was the best way to explain it really, but i thought it warranted mentioning that this money has been "saved up" during the year.
The figures I've used are straight from the top lines of the bills each month, so not removing the free hours octopus gives from time ro time as I didnt want to muddy the waters. They wouldn't make much difference anyway in the grand scheme of things, but I felt it better to be conservative with figures.

So short version is i used to self consume as much as possible and used 16000Kwh, I now export as much as possible, and deliberately fill batteries to max every night, so now I buy 29000Kwh and export 13000Kwh, and that 13000Kwh is enough to offset nearly all of my import.

Last year my off peak to peak buying ratio was 98.7%.
This year my off peak to peak buying ratio is 99.5%

So, can batteries save you money?
Your darn right they can, and for me, they are 

Qyburn

I changed to this strategy this Spring when they got my meter working. It still feels a little odd to be deliberately importing more than necessary. Example last September we imported 21.86 kWh, this September it was 175, but a combination of the off peak rate and increased export meant we were financing better off.

One issue that we have, which you may not, is that our panels are over subprovisioned vs our inverter and export. So in the Summer if we fully charged the battery off peak then all that "clipped" production would be wasted.

Martyn1981

Hi Solarchaser, similar changes made here. I switched to Octopus export tariff in May, giving up the FiT deemed export. At the same time, I too switched from charging the BEV's from PV, to using cheap rate instead.

I can't use my big batts for arbitrage, as they are DC side, behind the bi-directional TGM, so the round trip losses would impact FiT income. In fact my Nov-Feb generation figures on that system now show as ~50% of PVGIS target, due to charging losses, but Mch-Oct (no grid side battery charging) are normal.

But even so, looks like leccy & gas bill for this year will be about £750. Export income about £500.

Changing to Octopus export in late May, meant I earned about £120 less than if I changed earlier (but had to sort out FiT changes, and meter swops etc etc first), so would have been over £600.

Just installed HW tank (immersion) and leccy oven, so gas no longer needed and being disconnected in 2 weeks, so that will knock about £100 of SC's off the bill, bringing leccy bill close to export. [Gas savings, v's increased leccy at cheap rate, should balance each other out.]

So 'normal' leccy, space heating, cooking, DHW and transport bill, close to zero (net zero).* [But I should really include the 'lost' deemed export at ~£120, and an est £150 in FiT subsidy losses. But neither of these costs would impact somebody now/since end of FiT scheme.]

I pay ~£55pm, reclaimed some money at start of year, but balance is now ~£750 with Octopus. Without asking, over the last year or so, Octopus have reduced my payments from ~£150, to ~£75, to ~£55. I'm curious to see if they revise it again, perhaps ~£15?


*I appreciate I have a large(ish) amount of PV now, but many installs these days seem to be pretty big too. And  just the old PV on my main roofs is 4.4kWp, which today would probably be about 7.75kWp looking at current (but normal) PV panels.

So a new install could easily match me, without even considering lower roof/canopy and ground mount. Plus a carport or small pergola would allow ~3kWp, or twice that for a large pergola / two vehicle carport.

Add in wall mounted PV now that it's permitted development, and even PV/battery powerstation kits, and the potential is opening up / widening for many folk. Good times.

Heedtheadvice

All looks quite lucrative financially from all you all write.

A few queries and comments that perhaps address. Not a downer at all but just to get more info and your thoughts on risks!

1. Adding all the generation to me seems a no brainer in terms of self usage or exporting where that is possible. Do tariffs such as you are using require all generation/storage to be MCS certified or are they flexible in their approach.

2. Cutting  out one of the grid power sources ( gas) also reduces the standing daily charges which is not insubstantial over time. Have you factored in these costs/ reduced costs in your posts?

3. What is the effect on any potential reduced capital appreciation or income from same were you to have not purchased/increased solar/batteries/ tanks or reinstalled hot water tank and immersion heater after having switched to gas combi boiler on years gone by ( a common approach just having hot water on demand rather than storage.) I.e. not really going green at all 😞

4. How do you perceive risks? Two I can think of:

a) going all electric and power outages ( e.g. I have just gone to an EV from a PHEV and a log term area outage could be hard to handle so I still have a petrol backup as 2nd car; I still have gas currently as a main heating and a non electric backup). I am obviously risk averse!

b) risk of the current great tariffs being removed ( or much less attractive if/when circumstances change ) throwing the fiancial benefits off a cliff. e.g.20000kWh annually ( not unreasonable? ) at 25p per kWh is considerable. Unlikely perhaps for some time but would have a big impact on running cost and mitigation?

What a situation coming virtually full circle where many have been taking out immersion heaters over the years ( Solarchaser excepted of course 😀 ) and now they could be part of a better approach financially and greener!!

Solarchaser

Qyburn, I agree it feels weird, for many years I would try to guesstimate the next days solar to decide whether to charge batteries enough to see me through the next day, or hope the solar would do it, which meant looking at solcast basically every day.
Now It has no impact on me as the batteries are charged fully every night, and virtually all solar is exported.

Mart, good to see you on the journey too, kinda sucks about the big batts not being able to be used in the same way, but I suppose you always knew you were limited in what you could do due to originally being refused more solar.
I do wonder though if you could charge overnight, start exporting early, and then when sun is out, recharge the excess while exporting the maximum, and again in the evening export again from what's been recharged.
You will lose out on the round trip, but it would increase your export.

Heedtheadvice,  I do like your attention to the details, it has certainly helped steer me through some decisions on this journey 🙌

I'll do my best to answer your questions 

1. You need an MCS certified part of the install for Octopus to approve export, but not the whole thing, i asked this when I was exploring originally... well I asked if there was a limit to export, and was told no limit.

2. You are of course correct, no gas standing charge was a bonus,  but this i did 3 years ago, so I didnt include it in my figures here, as I wanted to show only the difference in moving from a "self consume as much as possible " model, to an "export as much as possible " model.

3. To be honest I've not looked at that. I am a bit impulsive when I have money spare, not really a saver, if you have a few grand spare, you take the kids away for holidays, you dont invest, or at least thats my opinion while they are still young.
So I cant answer that one im afraid.

4.a) there is a risk of a power cut, and if the power was cut then my larger batteries would let the house continue as normal in the summer, but in winter we would probably struggle as the source of heat is removed.
However from a risk assessment, you need to consider the possibility vs the historical data, andvive lived in the same, well populated area for a few decades and had only 2 power outages I can recall, both were under 6 hours.

If I were away from the central belt of Scotland, I believe id have a different view of this, but really that would probably be resolved by a back burner arrangement for the heat.

I dont think this is a concern in the short or medium term, as more wind keeps getting added, the low overnight tarrifs will continue, this was my bet a few years ago when I first went to an overnight tarrif and added several more batteries, and its held well so far.

However on the other side, the amount paid for export, i can see that being decreased, and/or I can see it moving to a time of day model, as right now I could charge until 05:30 and then export until 09:30 and be paid the same from octopus as exporting during the dirtiest period, and as part of this journey is about green not just money, I think exporting between 16:00 and 20:00 is best.

But if for instance the export tarrifs went down to a few pence in the middle of summer when everyone has the solar going strong, then id probably change back to solar charging in the summer,  maybe exporting early morning or early evening,  but I doubt it would be as lucrative as it is right now.

Since im over a year on export from octopus they have moved me from the guaranteed 15ppKwh to a variable export tarrif, this tarrif is still 15ppKwh, but you can see how they are giving themselves the option to change it, and from a business point of view, I can absolutely see why.

Finally yeah back to immersion for me, but im sure those who are doing heat pumps could be more efficient than I am, but happy wife, happy life

NedS

Heedtheadvice said:

4. How do you perceive risks? Two I can think of:

a) going all electric and power outages ( e.g. I have just gone to an EV from a PHEV and a log term area outage could be hard to handle so I still have a petrol backup as 2nd car; I still have gas currently as a main heating and a non electric backup). I am obviously risk averse!

Most gas heating/hot water systems will not operate without electricity, so it's not really a non-electric backup. At the very least they will require pumps to operate which run on electricity, so you're still going to be without heating in a power cut unless you have full home backup battery storage (e.g, Tesla Powerwall et al.)

To answer the title question, we run an electric house for free (excluding capital costs). Solar export in summer (Octopus IOF) generates sufficient credit to cover the bills (Octopus Cosy) in winter so the net result is net zero bills annually (although we don't have an EV, so are not including car costs)

Solarchaser

Hi Ned, could I ask if you are in a fairly modern and low occupancy house?

I ask this as there's no way my export in the brighter months would cover my heating use in the duller months.
For instance in the month of December last year I still exported £87 worth, I need that to be breaking even.

The other thing worth considering is how much you are willing to put up with, I have a friend who has solar, heat pump and batteries and makes a decent profit every year, however he and his good lady have their thermostat set at 15C, and Mrs. Solarchaser took ALOT of negotiation to settle at 20.5C on our thermostat,  and im well aware thats increased when im away.

I've no doubt many low occupancy houses can make a ,zero cost home fairly easily without batteries, mine was more to those with a larger family and so still requiring alot of hot water and heating, high usage homes, that you can still be close to zero cost, or more than.

Martyn1981

Solarchaser said:

Mart, good to see you on the journey too, kinda sucks about the big batts not being able to be used in the same way, but I suppose you always knew you were limited in what you could do due to originally being refused more solar.
I do wonder though if you could charge overnight, start exporting early, and then when sun is out, recharge the excess while exporting the maximum, and again in the evening export again from what's been recharged.
You will lose out on the round trip, but it would increase your export.

Hi mate, it's actually the loss of FiT income that means it doesn't work for me. Let's say I get 10% round trip losses in the summer (maybe 20% in winter), then I import 10kWh at 7p, and sell 9kWh at 15p, so I make 65p. But my bi-directional FiT meter will clock up 10 units import, 9 units export and a net reduction of 1kWh. With the earliest FiT rate now at ~74p, then I'd lose more money, the more I import, such as for arbitrage.

I knew this beforehand, not a concern. The DC side batts, allowed me to nearly double my PV on that array, whilst maintaing the same DNO 3.68kW approval, so that battery allows me to avoid day rate leccy prices with stored PV, and the winter grid charging at 7p is well worth it, even with the small FiT losses, as it means I again avoid day rate leccy prices.


@NedS - Same thought here, power cut will shutdown a gas boiler. I do now have 8kWh of powerstation batts, so they could be used to power the boiler ..... but they can also run one (or two) of my A2A units.

Maybe not the biggest concern, but losing a gas boiler in winter due to a fault with it, may be worth thinking about. As I have 2 A2A units, then even if one fails, I still have a back up.

And regardless of heating source, a battery installed with an islanding function, like Tesla's Gateway (others are available), does mean the house can continue happily, and the PV generation working too.

And then we have V2G/H/L ..... could go on all day (as usual).

Magnitio

We also have had negative energy bills since installing solar panels and batteries, despite charging an EV that does about 7k miles a year. Since Feb 2022, the totals are:

Electricity cost - £1,011

Gas cost (yes, I also have a wife who does not want a heat pump) - £1,435

Electricity export - £3,182

So, excluding the amount being saved on petrol, that's a negative energy bill of about £700. We withdrew £400 of credit and have about £480 remaining credit to see us through this winter.

The solar installation has a backup facility that allow us to use the battery/solar in the event of a power cut. 

silverwhistle

I have nowhere near that level of granularity in my information! :-)

FITs last four payments = £1009, and Octopus wanted £85 a month which I've reduced to £70 as I am about two months in credit and don't actually build up too much of a debt in winter. On my (very!) raw figures the standard FIT does me well and I'm not going to sweat the details too much.

<37 kWh of gas so far this month so getting rid of gas and the SC is my next aim. I'm on Agile with solar so DHW has largely been by solar (2 kWh today for example) or manually switching when Agile has been cheap. Judicious use of V2L to reduce the bad peaks. My average of 8p per unit sounds good, but unfortunately the more expensive Agile standing charge takes off the gloss, hence the importance for me of getting rid of the gas SC. If I were a heavier user the amount of SC per unit purchased would be a lot less.

With 50kWh of battery on the drive I'm not in a hurry to get another one in the house. V2L is a useful back up though, and so is the lounge wood burner.

michaels

I thought SEG payments were generally being slashed across the board, and of course you need to factor in AC/DC/AC losses and battery lifetime cycles.