Solar power for garden rooms

Last week we featured a solar powered garden room recently built by Crusoe Garden Rooms. The idea of a solar powered garden room really appeals to us, and we know it does to many readers of this site. Crusoe Garden Rooms customer had clearly done a lot of research into his options, and has very kindly answered our questions, to help other garden room buyers considering solar power.

What size and output of panel was chosen for the garden room?

The choice was made on the grounds of balancing initial outlay against the anticipated use that the garden room would get. The assumption was that there would never be a significant load on the system; lighting being the main one with occasional small loads for stuff like music equipment, laptops, battery chargers, etc.

There are plenty of suppliers of this type of equipment, which is popular with many off-grid types of installation such as caravans, boats, and even camping. This one is the 60W ‘Solar Power Station’ purchased from The Solar Centre which was available at the time with a 20% discount. Alternatives which look almost identical are also available from the ubiquitous Amazon and also other outlets such as Maplins (search for ‘solar panel kit’.).

The ‘60W’ in the name is the maximum output of the panel to charge a 110Ah deep cycle lead acid battery (not just an ordinary car battery).

Fully charged, the system therefore provides about 1KWh of mains electricity, with the time to recharge affected by the position / orientation of the panel and the amount of prevailing daylight.

What size is the garden room and how many power points and lights are there?

The garden room is the ‘Studio’ from Crusoe Garden Rooms: 5m × 3m with eight LED downlighters inside, and a 1m decking area around two sides, covered to the front of the room with an additional four LED downlighters. I’m not sure of the rating of each light, but I would guess about 3W: 36W total load for the built-in lights.

There are four double sockets around the room, all properly wired for use with 13A plugs, although there’s no way the existing power supply could support this level of drain.

Solar powered garden room

Is the panel the sole source of electricity or is there back up connection to the mains?

There is no mains back-up: all the electricity comes from the solar panel. It was a deliberate choice to be completely off-grid, accepting that an unobtrusive system also meant a very modest level of power available.

What sort of drain is being put on the power eg. is the room being used as an office all day, or is it just evenings listening to music?

As stated above, we haven’t ventured beyond the full lighting load so far. As we get the room furnished there may well be a modest music system installed, but nothing of huge significance. There are currently no plans to use the room as an office, but it’s absolutely plausible that any type of social gathering could increase the demand on the system. As we get towards winter we will see what happens. We initially considered installing a small wood burner at the time of the build, but have put that on hold until the heating requirements become more apparent. The room is very well insulated and we may be able to get away with a much smaller power requirement, especially with small heat exchanger systems becoming available.

Does the solar power work as well as you hoped in a garden room, would you recommend it to other buyers?

The solar kit was bought before the garden room and installed temporarily in the garden shed. It became apparent that the 300W modified sine wave inverter was going to be more of a compromise than expected for powering the garden room.

Firstly the modified sine wave (in which the alternating current follows a series of ‘steps’ rather than a true wave form) can mean that some appliances work less well, and secondly the start-up current of appliances can cause the inverter to trip out. This was true of the LED lights in the garden room which would only come on after the inverter reset and ‘soft-started’ itself after the initial spike of flicking the light switch. Fortunately I had done a bit more reading up by this stage and had bought a 1KW ‘pure sine wave’ inverter (widely available on line) firstly to avoid the performance issues of sensitive appliances and secondly to have the capacity to manage issues like start-up spikes. This system has worked perfectly for the demands on the system so far.

So yes, I would definitely recommend it as a system with the caveat that the choice of inverter – which delivers the a.c. voltage to the system – needs to have a much greater stated capacity than the steady-state power consumption would suggest.

Roughly how much did the panel cost to buy and how quickly do you think you’ll make your investment back?

The kit cost £636 with the prevailing 20% discount, and the additional 1KW pure sine wave inverter cost £85 (selected on Amazon with a minimum 4* rating, plenty of reviews, and with a significant discount at the time of ordering!). I will be spending about £100 more on the components to reinstate the principle in the garden shed with the now-spare 300W inverter.

It’s therefore a bit complicated, but for less than £1000 and by waiting for the right offers, I will have two systems providing off-grid power with no revenue cost. In terms of pay-back, I would suggest that this has already been achieved – and substantially more – by not running a mains power supply from the house to the garden room (60+ feet), although I can’t give any figures because it was never going to be quoted for.

I installed the system in the garden shed myself, although others may need to consider the modest(?) additional cost of getting this work one for them. I’m very grateful to Crusoe Garden Rooms who ran the wire from the panel into the room and then added the connection between the inverter and the consumer unit at no extra cost – this was very generous and much appreciated.

The long-term cost really depends on how long the battery lasts, as the deep-cycle types are more expensive to replace than the familiar lead-acid technology applied to car batteries. It is, however, already a widespread type of power source and this is likely to see the costs doing nothing worse than remaining static.

This is such valuable information, our sincere thanks to Crusoe Garden Rooms customer for taking the time to answer our questions. For more information about Crusoe Garden Rooms visit their website or give them a call on 07977 035 254


Visit the Garden Spaces websiteVisit the eDEN Garden Rooms websiteVisit the Gembuild website for garden offices & studiosVisit the Harrison James websiteFind out more about Green Studios Visit the Booths Garden Studios websiteVisit the Timeless Garden Rooms website Visit the Smart Garden Offices websiteVisit the Hideouts websiteVisit the ModBox Spaces websiteVisit the My Eco Space websiteSee what a garden room will look like in your garden