Taking advantage of economy rate electricity

I just heard of people that have set up battery power banks for the home although they don't generate their own electricity. In the UK at least you can have dual rate electricty, so you pay more at different times of day. By charging the battery bank at cheap rate and using it through the rest of the day, you can save a third or more of the cost of the electricity you use.
There is obviously an upfront cost, but what other down sides might there be? It seems that this would gve a certain amount of resiliance in power outages for example too!

Batteries, even LiFP, show slow deterioration with charge cycling.
So the difference in electricity rates needs to be enough to cover the depreciation of the batteries accelerated by charge cycling.
That may be why EV car makers are slow to offer the function; backup charge cycling might shorten car battery life.
It does work though.

Nancy Reading wrote:I just heard of people that have set up battery power banks for the home although they don't generate their own electricity. In the UK at least you can have dual rate electricty, so you pay more at different times of day. By charging the battery bank at cheap rate and using it through the rest of the day, you can save a third or more of the cost of the electricity you use.
There is obviously an upfront cost, but what other down sides might there be? It seems that this would gve a certain amount of resiliance in power outages for example too!

Thats a good idea actually. But how long would it take for this, to pay for the battery / pay for itself.

Because the batteries are quiet expensive

Mark Mcdoe wrote:Thats a good idea actually. But how long would it take for this, to pay for the battery / pay for itself.

Because the batteries are quiet expensive

I suspect you're right Mark, although it does build in resilience. For example, we have bought an uninterruptable supply for our little retail store, so that the till and PC carry on working through a power cut. If that were all we used then charging it at night and using the electricity during the day would be a bonus. We actually have a fair amount of refrigeration, so it isn't quite that simple, although we are looking at extending the system for the lighting (which we need through the day due to lack of natural daylight in the building.

According to go compare website the average cost in the UK for electricity per unit at night is about half that used during the day (for 'economy 7' tariff). For an average house in the UK energy use is about 14200kWh (ref. ofgem) so you could save up to about £2130 per year if you had a big enough storage unit.

A whole house battery unit probably costs c. £6000 ? So the payback isn't quite there yet (although 3 years isn't that bad, depending on battery life and electricity costs), but there may be a sweet spot for a low electricity user, or in combination with a solar PV set up perhaps.

Don't quote me, but I'm sure I read something about Australia offering a subsidy for these sorts of home battery banks in an effort to quickly improve the ability to store sunshine generated power. This way the homeowners get the money benefits rather than big business (like the Musk huge battery installation place), the storage gets diversified so less fire risk, and if done right, homeowners have back-up power when needed. I don't think owning solar panels was part of the requirement.

So yes, you need to crunch the numbers and consider all the factors. For example, I have a friend who literally cannot sleep without a CPAP machine who therefore can't sleep if there's a long power outage. It might take only one extra reason to make a marginal monetary gain into a lifestyle gain, like being on a well which requires power for the pump like we are.

Maybe one of our Aussie permies could find some info about what I recall reading and confirm its accuracy so far as details.

They are starting to come up with better home scale battery systems. They don't have to be light weight with high density like car batteries since they just have to sit in one spot. If more new battery tech is designed with this in mind, I can see the costs dropping. As always, the danger increases for late adopters by which time there's more night time demand for recharging batteries, and the rate difference between day and night use will decrease or disappear.

My crystal ball has some serious cracks...

Our rural electrical power cooperative offers "off-peak" electrical rates although it does come with some extra service charge that is supposed to be minimal.  I need to look further into this....not just talking to the cooperative, but to real users and what their experiences are especially as we compare usages and lifestyles.  Irrespective of the off-peak plan possibilities, I will be looking into a 24V battery system for a 10kW hybrid inverter/charger that includes an automatic transfer switch and solar-priority charging.  Most immediately, the system would function as back-up to replace years of starting and maintaining petro-fueled generators....and those generators were directed primarily to the deep well pump and sump pumps as well as furnace and lights.  With having just converted to propane for the furnace, we may swap out the electric hot water heater for a tankless hot water system (2 member household, minimal use).  With this approach to whole house energy at this point in our later years, the batteries should not be cycling too much and will remain topped up by a mix of grid-tie charging and solar charging.  As needs/costs require, we may introduce circuiting to judiciously transfer more loads to the batteries, reducing dependence on the cooperative/grid....possibly eliminating it altogether depending on changes in alt-energy market and cost of grid power.

Douglas Campbell wrote:Batteries, even LiFP, show slow deterioration with charge cycling.
So the difference in electricity rates needs to be enough to cover the depreciation of the batteries accelerated by charge cycling.
That may be why EV car makers are slow to offer the function; backup charge cycling might shorten car battery life.
It does work though.

This is really only an issue with fast charging, and it affects older chemistries far more than LiFePO. In a residential setup, you're never going to be dumping high current into the batteries and generating lots of heat. Some degradation is inevitable, but even worn-out first gen Nissan Leaf batteries are in lots of home systems now and they are likely to go twenty years or more before becoming bricks.

Hubby says that the analysis in this video about the larger context of renewable energy and batteries is the best he's seen/read, although the bit about growing corn as a biofuel we read a decade ago and is only applicable to the USA.

So although it's a side shoot of the first post, if people want more information, it is worth watching, despite its length.

Battery bank setups are expensive. If you have reliable grid power and smart metering for the peak vs. off-peak hours, would it make more sense to organize your high-use appliances with timers so they run when the magic juice is cheap?

Where I live, the electric co-op encourages you to get a giant, super-insulated water heater and use that as a battery. You can enroll your main power into the program where they can turn you off during peak demand times or get a second meter for just the water heater and maybe a few other things that are OK to turn off during the day and on at night. The electricity is something like half price.

That's easily the most frugal way of doing things Douglas I agree!
In the UK hot water tanks and heat storage heaters (electric not Rocket stove fuelled) are fairly common. We have electric storage heaters in our little store here ourselves which make heat from cheap electricity overnight and store it in dense blocks to release during the day. You can put timers on clothes washing/drying machines (and even electric ovens) to run overnight. No more investment needed and instant payback financially.
The point of the cheap rate is to spread out the grid load away from peak times here, so the electricity system has been set up this way deliberately. I'm assuming you have something similar in the US.

Nancy Reading wrote:I'm assuming you have something similar in the US.

I think it varies by venue. When I've lived in/around cities, they had variable rates -- but it was never so different that it changed our behavior. Where I live now, they just have an opt-in system where they have the right to cut you off completely during peak load periods, though they rarely have done so historically.