1.21 gigawatts

June 29th 2022, Our House, Derby

Though not part of the original plan for the tackling our messy loft and never more than something thing we “may” look at in the future, the recent increase in gas and electricity prices (plus the second increase coming later in the year) got us looking into installing not just solar panels but also on-site battery storage.

Our System

We clearly weren’t alone in trying to reduce our reliance on the grid and mitigate the impact of the ever increasing fuel costs. Getting solar installers to come out to survey our property took some time. Eventually we did and settled on the quote we got from UPS Solar.

They would install the solar panels, an inverter, a storage battery, a clever little device called an iBoost plus all the other bits and pieces required to fit the panels on the roof and the rest of the equipment in the loft.

Solar Panels

In total we have gone for 14 solar panels. That’s the most we can get on our 9mtr long south-west facing roof.

Solar Panel

Each panel can generate a maximum of 400watts each giving us a peak generating capacity of 5.6kw.


Those panels connect to an inverter converting the DC electricity generated by the panels to the AC electricity used in the house. Capable of delivering a peak load of 5kw it will actually be restricted to 3.7kw to start with to avoid lengthy installation delays waiting for DNO approval.


That means, assuming the panels are generating enough power at the time, the peak the house can use at any one time is 3.7kw. That is until we submit our application to the DNO requesting to increase that limit to 5kw max of our inverter.


We have gone for a battery with a total capacity of 7.8kwh. Unlike other systems the battery we have chosen is modular, each module providing 2.6kwh of power.

One battery module

We are having three to give us that 7.8kw total. You can add more in the future up to a max of 8.


iBoost is an intelligent hot water controller diverting any excess electricity, which would normally be sold back to the grid, and sends it to our immersion heater to heat the hot water.

How does it work?

The power generated by the panels on the roof will be sent to the house. Any power not used by the house will charge up the batteries. If the batteries are full that excess will be diverted by the iBoost to heat our hot water. If the hot water is up to temperature that excess will be sold back to the grid.

The batteries allows us to store and use electricity produced during the day in the evenings and overnight, when the sun goes in, reducing the need to use electricity from the grid.

The iBoost means our hot water may well be hot enough to stop our gas boiler coming on, reducing the need to burn any gas.

Finally selling back any excess electricity, though at a rate far lower than you buy it, means we might be able to generate a few Pounds per month in income.

Installation day

With the scaffolding put up a few days before Wednesday 29th June was installation day. Having unloaded everything onto the driveway the guys from UPS Solar set about installing the panels, inverter and electrical components.

Rails being fitted

It wasn’t long before the rails, used to secure the panels to the roof, were fitted and ready for the panels themselves.

14 Sharp 400w solar panels
Rear of the panel

The panels were far larger than I thought. Standing 1.72m tall, 1.13m wide and weighing 22kg each it’s fair to say they are huge.

Panels going up

Like most of the current crop of panels they are a nice sleek black colour rather than the blue panel in a silver frame the older panels had.

Panels being fitted

Being on the roof the panels are the most visible part of the system. The invertor, with its various wires, connections and breakers, was installed on the recently cleared rear wall of the loft.

Nice clear loft wall to fit things too
Inverter being fitted

Those wires go from the panels, to the inverter. From there they go its own little electricity meter, monitoring output, across the loft and through our existing trunking running down the side of the house.

Existing trunking extended
Trunking taking wiring from the inverter to our consumer unit

That trunking was extended to take the wiring across to our consumer unit allowing the electricity produced from the sun to power our house.

Solar PV added to existing consumer unit

Happily they we able to add this new circuit to our existing consumer unit saving us the expense of replacing it or the mess of fitting a smaller second unit alongside the existing one.

Solar iBoost going into our airing cupboard

The final part of the system being installed was the iBoost which was fitted in our airing cupboard and connected to the immersion heater.

IBoost and various clamps fitted inside our meter box

A small transmitter in our meter box with a clamp fitted to the meter tails monitors for excess electricity. If there is it turns on the iBoost controller and heats the hot water. As solar output fluctuates if there is no longer an excess it stops heating the water.

Install complete

The entire installation took less than a day to complete and a few days later the scaffolding was removed.

All 16 panels fitted to the roof

I’m really pleased with how sleek the panels look. Square on to the front of the house you can barely see them.

FoxESS Hybrid Inverter installed and working
Solar iBoost installed and working

The inverter install in the loft is equally neat and tidy as is the iBoost controller in the airing cupboard.

Generation to date

In the week since installation we’ve had a couple of cloudy days and a couple of very hot sunny day during which we have generated 164.2kwhs of power. At today’s prices if I used that electricity from the grid it would cost me £49.26.

Todays generation data

Right now despite it being overcast its generating 1.59kw. That’s enough to power the house and sell back just over 1kw back to the grid. Over the last few days that generation figure has been as high as 5.3kw, pretty close to its 5.6kw max.

Normally we consume about 13kw of electricity per day at this time of year. Since the install that’s down to just over 4kw. Plus we are generating a surplus to sell back to the grid. Though that arrangement is not yet in place (my application is currently in progress) if it was that would have earnt us £11.49. We are saving and earning at the same time.

iBoost diverting 1.20kw of power to heat our water

The iBoost is a real star. It’s diverting excess power that would be sold back to the grid and heating our hot water. So far it’s diverted 14.16kw of electricity and meant our gas boiler doesn’t come on in the evening, as scheduled, to heat up the water. The iBoost had already done it. That’s reduced our gas consumption from an average of 14kw per day, at this time of year, to 4.5kw. Our gas will never be zero as we have a gas hob but it’s certainly a big saving.

Finally there have been hours at a time where we have been completely self-sufficient. There was enough surplus power to run everything we had on at the time, which often included our dishwasher, without any need to pull power from the grid. That’s a very satisfying feeling.

Weren’t you having the batteries?

Due to high demand for solar installation getting hold of batteries is proving difficult. Ours weren’t here in time to be fitted with the panels. UPS Solar did make us aware of that before we agreed an install date. They also confirmed our batteries are expected off the boat coming from China at the end of August.

Current generation as shown in the app

Until then we have plenty to occupy us understanding how the system works, what the app is telling us whilst making sure as much excess power is diverted as possible to our hot water tank.