Wonder Watt and Monitor (Scheduling with an Uncertain Future for GivEnergy) – Solar #12

Introduction:

After 18months use I was falling out of love with the GivEnergy (GE) native scheduler, principally because of poor documentation and support, but also because the scheduler is not ‘set and forget’ nor optimal as promised, principally because of:

• disabled battery bug – impact: not robust when consumption varies; even with seasonal discharge timing adjustments, this bug has a financial impact.
• no integrated weather forecast – impact: even with seasonal adjustments to the charging time this has a financial impact.

The final ‘nail in the coffin’ is our plan for an EV later in 2026. I wanted 3rd party EV charger integration and so I explored the Wonder Watt (WW) scheduler. In Nov 2025 I subscribed while we are still using Octopus Flux, principally to confirm WW robustness and operation, ahead of EV purchase, but also I was intrigued to see what impact WW could have on our ROI, with the Octopus Flux tariff.

Now (April 2026) that GE is in administration with the promise/hope of a paid for cloud portal, I have been experimenting with Monitor for Android, to understand if this is an option if the GE cloud portal is switched off.

In this post I have discussed my experience with these 3 schedulers and the Octopus Flux tariff:

• Native GivEnergy Scheduler: 20 months use
• Wonder Watt: 5 months use
• Monitor: experiments leading to 2 days where Monitor scheduled our system with the WW schedule disabled.

Just as I come to publish this…

I wrote to GivEnergy Software, Andrew Miller (Monitor) and Wim (Wonder Watt) to get their comments on this post:

‘GivEnergy Software’ stated that the GivEnergy [native] scheduler will be made obsolete with…

…“new Premium / Standard Tiers. The Standard Scheduler works directly (similar to your Monitor column) while the Premium Scheduler has also been completely revamped and comes for free with Premium, unlike Wonder Watt which incurs an additional charge on top of Premium (because it uses GivEnergy’s cloud infrastructure to work its wonders!)”

This sounds intriguing to me and, as long as these come with a manual and are easy to use, I hope to find time to give them a trial and write up the result.

And, Andrew Miller pointed out that Octopus Flux is temporarily unavailable (for new customers I assume, as it still looks fine on my Octopus app!):

Wim thought that the below is a fair write up!

Summary of my current view:

• Wonder Watt is my preferred solution – it is pretty much ‘set and forget’; gives close to maximum ROI & should work well with 3rd party EV chargers
• Monitor: looks like a good scheduler if the GE Cloud Portal goes down. Will require some simple seasonal adjustments to cheap rate charging, so not entirely ‘set and forget’. I expect  ROI not quite as good as for Wonder Watt & no external links so that the battery can make use of tariffs like Intelligent Octopus Go (IOG).
• GivEnergy Native Scheduler: Seasonal adjustments to charge and discharge are required and even then not optimal. I have limited trust & so would be wary of external integrations for tariffs like IOG

Comparison of how they work

Example Schedules:

Monitor for Android

The Monitor scheduler gives the most flexible access to scheduling parameters.

Wonder Watt

Wonder Watt Performance Vs GivEnergy Native Scheduler

First and, for me worth the £54/year subscription, Wonder Watt is pretty much ‘set and forget’ (the original GivEnergy promise). Below I detail the gains:

• Financial gains (I will have a better idea after a full 12 months)
  • Disabled battery bug resolved
  • Weather forecast to control cheap rate / night time charge
• How WW enables a (mostly) ‘set & forget’ schedule

Note: the following is based on my experience that is limited to my set up (5kW, gen 3 inverter, 9.5kWh battery and ~5kWp solar panels), Octopus Flux tariff and, for WW, operation during the winter and early spring.

Disabled Battery Bug: Impact on Discharge:

WW resolves the disabled battery bug; this is key to ‘set and forget’ operation. In addition, the ability to robustly discharge based on %SOC minimises consumption at peak rate.

The following data from my Octopus app compares the period 20th Nov to 20th April using the GE native scheduler (24/25) and the WW scheduler (25/26).

Example of GivEnergy Peak Rate Discharge Fixed by Wonder Watt

The following graphs show a peak rate import example using GE Native Scheduler (in this case a time based discharge to avoid the disabled battery bug, before using WW):

After setting up a WW schedule, discharges can be based on %SOC as well as time and this issue is fixed, hence the reduction in peak rate demand.

But Wonder Watt Doesn’t Fix All Peak Rate Discharge

However, there is still some peak rate demand. One situation is caused by the physical limits of the inverter/battery:

Another case could be fixed with further development of the WW scheduler (indeed Monitor allows for this):

Here, if WW had the capability to schedule a higher battery reserve in ECO mode during the day, then we could be sure to enter peak rate with a decent battery charge. It is interesting to note that it looks like Monitor can do this (but I have not tried it yet)

Summary of the WW Disabled Battery Bug Resolution

The saving in peak rate demand goes part way to paying the WW subscription (but I suspect this saving is mostly in the winter when we often start peak rate at 4pm with <<100% SOC). There are opportunities to develop WW to further reduce peak rate demand.

With WW not only can we reduce peak rate consumption, I am also better able to control the SOC% at the end of peak rate. I definitely want to be at 2am with an empty battery ready to buy at cheap rate, but with Octopus Flux it is slightly better to export as much as possible at peak rate, as opposed to buying at standard rate (7pm to 2am) – 29.3p/kWh Vs 25.3p/kWh as of Q2 2026. I am sure that there is some £saving here, but so far I have yet to calculate this.

Wonder Watt Weather Forecast

The weather forecast feature is used to decide how much to fill the battery at cheap rate during the night. This is seasonal; based on last year, my theory is that, in winter and summer the forecast will rarely come into play; I would not go far wrong if:

• In winter I filled the battery every night at cheap rate
• In summer I only fill the battery to, say 25%, until the sun takes over.

For our system, the WW weather forecast feature is making an impact in spring and autumn.

I am sure that there is some clever maths/statistics to optimise the key settings:

• ‘daily use’ parameter in the settings
• ‘charge at least’ %age in the ‘smart charge’ task in the schedule.

So far I have only gone as far as to check that the mean forecast is about right (& it is) and I also calculated the standard deviation of the error (~4kWh). The daily use figure also has a mean (around 11kWh for us) and a standard deviation (not yet calculated). Then throw in the Octopus Flux tariff (that is tweaked every quarter) to decide if I want a bias in the settings (eg should I err on the side of a little to much charge at cheap rate or go the other way and be happy with a higher risk of running out of battery power before the sun is fully up and powering the system?). On top of that, with Octopus Flux, I am actually bothered about the 5am to 4pm daily use figures and weather forecast, but the weather forecast is for the full day…

…I have settled for a more heuristic (‘trial and error’) approach:

• daily use: set to 8kWh (high end of our 5am to 7pm usage) and will tweak to ensure that we mostly hit 4pm with 100% charge (the ideal is to hit 100% at exactly 4pm!) – hopefully by the end of autumn I will have a figure that is fixed.
• ‘charge at least’ %age in the ‘smart charge’ task in the schedule. I have been adjusting during spring – as of 13th May it is 15% & I daren’t go lower in case we get up early & start the dishwasher, etc (or the sun gets up late). In the autumn I will have to keep nudging this figure up as the sunrise gets later – I will just watch that the early morning %SOC minimum (before the sun gets up to full power) does not go below 4% (too often).

When I have a full year’s data, with weather forecast, I will see if I can place a value on a daily weather forecast as opposed to my previous seasonal adjustments. My view right now is  that it gives me a (close to) ‘set and forget’ setup & some easy savings in spring and autumn.

Summary on Impact of Wonder Watt

I really value the ‘set and forget’ impact of WW. While some tweaking during the year, of one parameter (‘charge at least’) has some benefit, it is probably small. WW brings the effort of running a solar system down, much closer to other (financial product) investments.

I can already see a winter time gain of £1.20/month from resolving the disabled battery bug; I expect more significant savings to be apparent when I have a full year’s data, chiefly from the weather forecast impact on spring and autumn and better control of the %SOC at the end of peak rate, again from resolving the disabled battery bug.

I am currently using a heuristic (trial and error) approach to setting the two weather forecast parameters. There is probably a more sophisticated statistical approach that would have a (small?) financial impact. These would need to be adjusted as Octopus tweak their Flux tariff each quarter…

…maybe the subject of another post.

EV chargers:

This is just theory for now – my EV is not arriving until November. I think that there are three objectives here:

1. Ensure that the home battery does not charge the car
2. Allow the battery to be charged at cheap rate, ideally in ad hoc charge periods provided by tariffs like IOG.
3. Flexibility for future tariffs

(2) and (3) required the GE cloud API to be operating and Octopus/electricity suppliers to be linked and support GE and the EV charger. I understand that WW will integrate with IOG and also prevent my  GE battery discharging to the car.

I understand that (1) can also be ensured by locating the GE current sensor before the EV charger, so that the EV can charge from the grid without the GE inverter sensing this and discharging the battery to the EV charger.

I am going to opt for this hardware implementation now that the future of the GE cloud portal is somewhat uncertain over the hoped for life of my GE system. The downside is that as tariffs change over time I might, in the future, want the flexibility of power source for car charging.

GE Administration: Hope for the Best…

…Plan for the Worst:

My wife’s old Samsung A21 Android 12 phone, complete with sparkly pink cover is on hot standby, powered up, Monitor loaded and ready to go:

Monitor App on hot standby

It is also gathering data, so I will have some data history if the ‘plug is pulled’ on the GE cloud portal.

My experience is that learning how Monitor works, and how to use it, was a whole lot easier with the GE Cloud Portal up and running, so that I could see inverter registers update based on Monitor’s schedule and parameters. I am glad that I bought this now as an insurance and have to ready to go if required.

Selecting a New Inverter

I am told that a typical inverter lasts around 10 years, so my GE inverter will need to be replaced before the solar panels (25 year predicted life). I also assume that a direct GE replacement will not be an option, so one day, I will likely need to select a replacement. Scheduling is certainly something that I would be investigating more thoroughly if/when I replace the GE system.

The Future of the Home Battery Market

As I wrap up this post I cannot help but reflect on the time that I have spent trying to get a reasonably optimum ‘set and forget’ schedule. Scheduling, to me, is one of the major weaknesses of the GivEnergy product.

My view: for wide adoption then the industry must target a system that your granny would be happy with – savings are proven/guaranteed and make it an obvious thing to install and, once installed, it is really easy to use…

…my sense is that those of us currently with solar/battery systems are enthusiasts. If these systems are to be adopted by 1,000,000s (as opposed to 10,000s), then the industry is going to have to do better than GE has done. This should not be impossible – there is plenty of complex tech that is used by 1,000,000s of people (phones, cars, printers, microwaves, etc); I would be intrigued to hear from other’s on your experience with different inverter/battery manufacturers.

Another comparison is to think about where else I might invest my money:

• The Nationwide Building Society
• Hargreaves Landsdown ISA or pension
• etc

All of these have pros and cons compared to a solar/battery system with different returns on investment and risk profiles, but all are ‘set and forget’ and, so far, none of these has required me to get to grips with 3 scheduling systems and, now, with the possibility of two more to try out!