A few of my work colleagues have recently purchased EVs (they all have non-EV cars as well) and they seem happy with them for what they use them for. They have talked about cheaper electricity for overnight charging at home: effectively benefitting from the grid ‘dumping’ excess night time generation at cheaper prices. This lead me to research this a bit more and there seem to be quite a few people out there that use an EV tariff to reduce their general power bill for all household appliances. Could someone explain to me how this works and, bearing in mind the significant fuel poverty faced by millions of British households every winter, why these cheaper prices for electricity in particular are not being offered to those who would benefit most financially?
I recently conversed (via social media) with someone who said they used about 900kwh of electricity and 400kwh hours of gas (I think per month) yet they only paid £9.31 over a 4 month period which sounds extraordinary to me. I assume they must have some form of solar panels which they sell back to the grid but even then, bearing in mind much reduced output from solar over winter months, I still can’t see how this adds up.
For the record we live in a 4 bedroom detached house that we own (fully in 10 years time) and have plenty of off-street parking and a double garage. We have toyed with solar panels but have been put off by the ‘ponzi’ schemes of a few years ago, the initial cost/vs return on investment and the limited life span + the bulk of our power bill per year comes from our gas central heating, despite never having it above 17 degree Celsius. We could invest if we thought it pertinent to do so.
What concerns me is those households who:
rent and have no say (for obvious reasons) in whether panels are installed.
have low incomes and can’t afford to invest in new technologies, be it EV cars or solar panels.
live in flats/apartments/terraced housing where solar panels/home chargers etc. are not a realistic option.
don’t have a car at all and therefore may be excluded from cheaper domestic power because of this, despite not contributing to congestion/traffic/on street parking in anyway at all.
I am aware of Economy 7 but I understand that these tariffs increase the cost of electricity during peak times so, unless you have night storage heaters and live a nocturnal life, the benefits are limited. Growing up we had a purely electric house with underfloor (Roman style) heating using blown hot air - it was very nice but cost a fortune to run. The system charged on Economy 7 overnight but despite this, the yearly electricity bill was over £1,000 pa back in the late 1980s/early 1990s.
FWIW we use Octapus E7 and use a battery. Typically the battery powers the house through all the peak period. Brought power bills down by about 60%.(we have PV as well but I have removed that element as that is further savings.)
95% of usage is in the low cost window of E7
Our house is oil and electricity… so showers, cooking are all electric. If there is no solar to speak off such as a heavily overcast winter’s day, then cooking a full Sunday roast for family etc will drain the battery by about 8 pm… but we only occasionally have grand Sunday roasts.
Also the battery output peaks at 3.8kW so anything above that is taken from the PV and/or mains.
Battery is a GivEnergy 9.52kWh battery - the maximum load from it at anyone time is 3.8kW. Anything above that is taken from the mains… the PV is always used first … right now it’s being trickle charged through the the thick cloud from this mornings use. So far today (since 7.30) 1.4kWh has been discharged from the battery - but light breakfasts here - as we are all out later.
The battery costs about 3k - give or take. We had it installed with the inverter when we were having PV panels fitted - it was easier to get it done together… so installation costs will vary.
We keep the inverter, battery and related switching gear all in the garage. It fits up against the wall and takes very little space.
Unlike gas central heating gas power stations can’t be turned off and on to match demand although I expect they have a range of output at which they operate effectively.
I guess the way the grid works is that some power stations are contracted to provide base load and get a lower price than those who top up.
Solar and wind are variable and you may have read that some are paid not to output to the grid when there is too much wind.
Most people don’t use much electric outside of peak times for which the spot market rate is much higher and more variable than the standard average rate. So it’s not that people are being cheated.
Octopus can install a heat pump in a reasonable insulated average home with the HMG grant covering most the cost. The trouble is that too many people rubbish heat pumps because they don’t understand that large radiators at 32c can still heat a room if the heating runs long enough.
Great information thank you. What do you expect the lifespan of the batteries to be? 10 years? 20?
Do you use Lithium based cells? I understand these are more compact - a (very expensive) upgrade when I had a Lotus was a Lithium Ion battery.
Would there be any real benefit to a household investing in batteries without solar PV and using an economy 7 based tariff to charge the batteries overnight? I assume the higher the proportion of domestic power is produced by electricity the greater then benefit would be - those with gas combi boilers would benefit less?
Hi Phil,
This is certainly true of today’s nuclear power stations (think 1-2 days response time) and the old coal power stations.
The most efficient gas power stations, those with a steam turbine on the back end of the gas turbines (so called CCGT, or combined cycle gas turbine) also need time to spool up.
So called open cycle gas turbine power stations, i.e. those without a steam turbine, can spool up very quickly and can easily be kept “spinning” on idle and come on line in a few seconds. They are however less efficient than the CCGT, circa 40% efficient vs. circa 60% for CCGT.
If governments wanted a pragmatic transition from e.g coal to renewables (with storage), a few more gas power stations would be a pragmatic and relatively affordable way of providing both baseload power and infill power, until we find a way to provide a green, resilient power supply system.
Yes I’m aware of the peak/surplus nature of the grid. Personally I just think the variation in pricing could be more equitably distributed between peak and off peak use so that the benefits of cheaper pricing can be more widely spread, especially for those who have little/no chance of having cheaper to run technologies installed.
Unfortunately, people were encouraged into gas (originally considered cleaner than fossil fuel electricity) domestic heating which, I assume, is the bulk of most costs - though our current EON rate is 5p pkw for gas and 20p pkh electricity.
Regarding over production, I recently read that last year £773m was paid to compensate producers for low demand periods and this year we are on course for it to be closer to £1bn - clearly a good business to be in…
Do the heat pumps need to be installed on the outside of a building?
…or we asked Octopus about an ASHP but were rejected because the UK construction industry went through a 20 year phase of using microbore copper central heating pipes that are fundamentally unsuitable for the higher water flow rates that ASHPs need.
FYI, watch out for a small UK company called Biaco. They have developed a new type of electrical boiler that will be a straight installation swap for a traditional domestic gas boiler, yet uses no gas. Better still, no need to change radiators or pipes.
The absolute killer is that it uses HALF the electricity of an equivalent ASHP, I.e. it is twice as efficient as an ASHP and has a total installed cost of a gas boiler, so about 25% of the cost of an ASHP system.
We have decided to keep our gas boiler until we can try a Biaco one
Admirable sentiment, but your rate is much lower than the spot rate by a factor of 2 at the moment. People need to be incentivised to change to their consumption patterns and total usage.
I’ve been paying £25/month since June 2023 and I think I may get through the winter just in credit despite a poor year for solar where I am. I am not going to loose sleep worrying about the return on investment. It is the right thing to do.
Yes. They work in a similar way to a fridge, albeit in reverse. They take in piped cold water and send it out as warmer water. To do this they take in outdoor fresh air, “suck” heat out of it and expel it as colder air. So you really need the air to be expelled outside.
You are right the options are limited. Most cheaper tariffs are overnight use due to that being when electricity is cheaper due to demand. They can be very helpful but only if you can make use of them by shifting times when you turn things on like the dishwasher and washing machine.
Solar on its own does not really help much with using a cheap overnight tariff but can significantly reduce one’s consumption from the grid. For overnight tariff use, it is more important to have storage battery capacity that can in the winter at least be charged overnight and the cheaper electricity used during the day.
Eon do allow their EV tariff to be used by people with storage batteries but do not have an EV. with a 6.9p/kWh 7 hour overnight rate it can make electricity cheaper. but only if you can avoid daytime usage from the grid using solar and/or storage batteries. The daytime rate from Eon is about 30p/kWh for the daytime rate and the standing daily charge is usually a little higher too compared to a std tariff.
We do have an EV (which we really like and would not go back to a combustion engine car) and we have solar on the roof with storage batteries. We do not use the daytime rate even in the winter due to that. The solar export just about covers the daily standing charge as where we live it is just about the most expensive in the country at 67p per day.
Hi the battery Warranty is 12 years - you can expect 15 or so - though the storage capacity will start to decline. They are designed to be discharged daily - and they cut off discharge ISTR is 4% capacity.
The battery cell chemistry is LiFePO4
Would it be worthwhile to use a battery - it can be depending on usage pattern. The E7 option works well at the moment as the wholesale spot rates have been generally quite high, though with all this windy weather the cheap rates have been rather low for part of the day… there are other tariffs such Agile, Flux and specialist ones for EVs, Heat Pumps, and storage heaters - all slightly tailored to that need.
The most expensive time to use electricity is between 4pm and 7pm, so some options are to buy the electricity to charge the battery and then sell back between 4 and 7 when the spot price increases significantly - it just means its best to shift any heavy usage from 4 to 7pm and this can be automatically managed for you… there are many options.
We might go Agile or Flux in the summer months - and pop back to E7 from October to March. ITs all quite easy with Octopus - and I suspect it is with other providers too… it is noticeable the solar generating significantly diminishes in Winter when the sun is very low in the sky… at least with our setup.
Lots of useful information from everyone thank you.
Bluesfan, this new boiler technology sounds very good - I assume it will require minimal disruption to one’s existing system too? Being developed by a British company and hopefully made in the UK would be even better - let’s hope they are funded properly.
We have A/C ‘exchangers’ in my classroom at work - they are quite effective but unsightly on the outside of the building and produce condensation which, if not regularly cleaned out, stinks like vinegar - the children hate the smell. The filters are accessible but the drip tray requires disassembly of the whole unit. Are heat pumps similar to this or better?
Interesting information Robhino ref the standing charge and solar panels - in the summer our bill is barely much higher than the standing charge for either gas or electricity. The winter is different, especially gas.
My takeaways so far are:
For non - EV home owners (whether they own a car or not), solar panels and more specifically battery storage (to take advantage of solar and cheap night time electricity) it worth doing, especially if you have a non-gas based heating system.
Heat exchangers are an option for some and grants exist but they may not be compatible for all buildings - pipe work issues and I assume’ grade listings may hamper their instillation?
this new electric boiler technology really could be a game changer provided you can obtain electricity at cheap enough prices compared with gas.
for those who live in rented accommodation the options are very limited, especially if one’s landlord has no interest in spending money/dealing with the potential hassle of organising new technologies being installed - particularly if there are potential teething troubles. From the ONS website:
In 2021, 62.5%, (15.5 million ) of households owned the accommodation they lived in, 37.3% (9.3 million) rented their accommodation and 0.1% (33,000) of households lived rent free.
Biaco look a bit smoke and mirrors. Taking energy from water is an idea not yet proven and there is no product available that I can see. They seem to be telling a story to attract investors, which is fair enough, but I’d need to see a developed and tested product before booking the installers.
I assume you meant water source heat than just energy as one of the oldest technologies in the world is the water wheel to create usable energy in the form of mechanical or more recently electrical energy etc.
There are several available water source heat pumps available for domestic and commercial use. It is not so different from taking heat from the ground.
I do not know of Biaco so I do not know what they are proposing.
Hi Bruss,
re your first sentence, an understandably sceptical first impression but not so. I have seen it working first hand and several university professors are very excited about it as they have proven that it doesn’t break any law of thermodynamics.
re your second & third sentences, the primary output is steam which then passes through a heat exchanger to produce warm water where this is required. Most industrial applications want the higher temperature steam. You are spot on about the technology being at the prototype stage rather than being an off-the-shelf production item. I’m very happy to wait a couple of years though.
In my case the microbore works because the pipe runs from the 22mm main distribution pipes are short enough. It was a risk I took based on testing at low flow temperatures with the old rads and gas boiler. All my rads were upsized and the house is heated with 32c water (36c from the ASHP to the heat exchanger. I went with an installer that didn’t demand unnecessary and costly pipe work changes.
The heating is a bit like a supertanker - it takes a while get up to speed. Therefore we set the controls to avoid big temperature drops. It’s only in freezing conditions we need to heat 24/7.
Not quite, as all that condensation and associated smell stay outside with the ASHP. All that comes inside is piped warm water for the radiators. No drip trays or filters inside.
