Battery Storage Q&A with the Experts

Hi everyone,

I hope you’re all keeping safe and well.

My name is Peter Verso (@Peter_at_Immersa) and I’m here with StJohn Bickley (@StJohn_at_Immersa) to chat with the Bulb community. We work at Immersa and we specialise in energy storage that supports the predictability of renewable energy. We’re here to open up a Q&A with Bulb members on all things energy storage.

Bulb started a battery trial last year as part of their product offerings in partnership with us. This battery trial is aimed at members with solar panels, to try and help them make the most of the energy they generate.

Bulb gets the batteries to members and communicates with them to track their experience, and at Immersa we handle the technical things - battery shipments, engineers, site surveys and installations.

Please fire away with any questions you have about all things energy storage, we’ll be happy to help with all we can and there will also be agents on hand to help with account specific queries.

Have a lovely day!

Kind Regards


Hey @Peter_at_Immersa and @stjohn_at_immersa - it’s great to have you here!

We had a great question from @Smart_fitter yesterday that maybe you’d be able to answer or give some insight on. They asked:

A few years ago I was thinking about getting myself a couple of solar panels and hooking them up to a battery bank then using an inverter to convert battery power to mains power. I am curious to know how big a battery I would need to supply say 5 kWh a day.

:smile: Georgie

Hi! I have a similar question. What does the 3 kW output mean? Will my battery storage be used up if I turn on my kettle?

Thats a great question and as always the answer shows that solar and battery is never that simple.
Solar panels typically generarte DC power and when they are linked together this makes quite a large DC volatge, in a typical installation can be up to 900V so it cant be fed directly into a standard battery.
Normaly it would be turned into AC first, this energy used within the property first, then the battery storage system would grab the excess, convert i back into Dc for the battery. Typically for our system we would suggest the Smile B3 with the extra battery module to give 5.8Khw of total storage and 5.6Kwh useable storage. hope this helps


Hello Audy
3Kw ouput means that the battery system will produce 3kw of power. So yes the battery will run the kettle. In fact when the system is installed we run a “kettle test” just to check that it has been all installed correctly we ask the kettle to be switched on to check that the system picks this up and starts to discharge!
The good bit is that it actually takes very little capacity from the battery. The kettle is only on for maybe 3 minutes to boil. with a 3kw kettle this means the enrgy it uses is only 0.15kwh!! so you could boil the kettle more than 18 times on a single battery charge ( Smile B3 without extra battery).


@stjohn_at_immersa I don’t have solar panels, is there any other way to get use from a battery?

Hello @ol1verb1rch. Indeed there is . If you have an electricity tariff like Economy 7 (or similar)where you have periods of time with a lower electricty cost, the battery can be set to charge during this period of lower cost, and to discharge at the time when your electricty costs are higher, so reducing your consumption of electricity at the higer tarif rate.

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Just wondering and I’m pretty sure that I know the answer but if we get a battery with a 3kw out put and we’re say boiling the kettle and the oven’s heating up, will it pull from the solar panels, then the battery and if that’s not enough power rom the grid as well?

Immerse are due to come to our house on the 23rd to do a survey, I am super keen to get batteries. My parents have batteries and a very low electricity bill as a result!

However, we are desperate for them to be installed in our loft. It is boarded and surely if the fitters wore the correct PPE there wouldn’t be an issue re COVID?

Hi @Mikeyb yes exactly that order during the day. Solar first then battery to top up if needed then finally grid. At night the battery will engage aon its own and then be supported by grid if required.

A colleague will reply on the other questions shortly

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Hey @Mikeyb - I’m going to pop you an email now with a bit more detail about your other questions!


I was recently dissuaded from getting a battery system installed with Bulb because my solar system capacity is 9.1kw according to my installer. And the Alpha Smile B3 only has 2-3kw.

3kW x 17p per kw = 51p x 175 days in a year = £89.25p extra saving per annum at an extra cost of £3k or so.

So is there a risk for potential customers? Spending £3k and not making enough back.

Look forward to your thoughts.


@col1 thanks for your question. We need to diferentiate bewteen power and energy in thi case. the Smile B3 charges and discharges at 3Kw (power)and has an inbuilt 2.9kwh battery (energy). the battery capacity is modular and can be expanded in steps of 2.9kwh. I this instance a large battery of say 8.7kwh would absorb more of the excess energy. Also the batteries are continuosly looking to charge and discharge so we see that often the system can make multiple cycles per day. we have quite a few systems now with the larger battery capacity.
Also i isee you ahve calculated at only 175 days in the year? we see the battery working 365 days a year. There is also power price inflation to factor into the equation.
Overall we see excellent returns on investement over the life of the product.

That ties in with what our installer recommended with the power vault (8kw) saving us more money per annum although at a higher price to install. Savings per annum are closer to around £300 and so paying off the battery would be shorter.

(175 days was down to the tariff we would have in place according to the installer - this I will double check. )