Electricity is supplied by two solar panels to two battery banks. There's a detailed description of the arrangement here.
When I started sailing, I navigated using a sextant, compass, radio direction finder and depth sounder. That was it. I was able to get a position line from a sun shot in 4 minutes, and a fix from 7 stars in 30. But it's quite a bit of work, and conditions have to be right. Sometimes it's cloudy for days on end.
These days, I use GPS, and carry a plastic sextant and a few paper charts in case lightning strikes or something catastrophic happens to the GPS. There are several GPS sources on board, including my phone.
I have no plotter. I find them very expensive compared to a laptop, and very limited. The laptop is no good outdoors of course, but I navigate indoors, and I can put the laptop on the table facing the door and watch progress like that if I'm hand steering. OpenCpn is a great navigation program, free, open source, and improving all the time. I've tried commercial alternatives, and greatly prefer OpenCpn. It has many chart options, and the laptop contains all the charts you might need.
At night, single-handing, I have a bed in the saloon, and have the laptop on the table. I hardly have to lift my head to see the chart, overlaid with AIS-provided ship's positions. It can sound an alarm if a ship is too close. The dashboard within OpenCpn lets me know the boat speed etc. at a glance. OpenCpn has an excellent night display.
Using a laptop instead of a plotter is more versatile and cheaper. And of course it can be using for a log, blog, image editing, email and whatever else. I have a wifi antenna that usually picks up a signal from an anchorage, so the internet is available. Weather files (grb files) can easily be downloaded, and are best viewed in OpenCpn, often showing local wind conditions every three hours as well as more general conditions up to a week in advance.
I am so dependent on a laptop for navigation, I had three, but one didn't make the whole journey. So now it's down to two. The spare is loaded with much of the same software, and it is quick and easy to replace on with another. Another source for navigation info is the phone with the Navionics app. The charts of this app are frequently updated. While it's awkward to use with such a small screen, it is great as a backup, and there were times when the Navionics charts on the phone were far more detailed that the charts on the laptop.
If I wanted to spend more money on navigation equipment, I'd simply buy another laptop. The laptop on the boat - a Thinkpad - is easily powerful enough to run all the software and is pretty frugal on electricity use. In fact, one of the reasons I chose the Thinkpad was that it has a built in power reduction system. Running the laptop at minimum performance, it still easily handles OpenCpn, but uses very little power.
Here's a link to my blog where I describe sailing using OpenCPN with AIS
The boat is fitted with a CruzPro PcFF80 fish finder/depth sounder, which displays the depth on the laptop. I have that from when I was running the boat as a commercial fishing boat. It wouldn't be my first choice for cruising (more expensive than is required) but I hardly use a depth sounder these days. I used to use one all the time coastal cruising, as it was often a source of another position line, but now I just rely on GPS and charted depths - even when I have to go a long distance through very shallow water.
Scrumpy has an AIS transponder. It's a fabulous tool and I wouldn't want to be at sea without it. AIS needs a VHF antenna, as does the radio. Two antennas at the masthead causes interference, so I have one antenna mounted above the deck. Usually, the AIS is connected to the masthead antenna. Sometimes I've seen ships hundred of miles away, but all ships within 50 miles is more common. So the VHF radio is connected to the lower antenna, giving it a range of 5-10 miles, which I find adequate. It's simple enough to swap antennas round if you need to make a longer range VHF call.
The fact that the AIS sends out a signal to other ships is great. I remember seeing a tanker coming up from astern as I was sailing down the Portuguese coast in a light wind and fairly big swell. I had the spinnaker and full mainsail up, and everything was tied down tight to keep the sails from flopping about in the swell. For me to move out of the tanker's way required a course change that would need the spinnaker over the other side - quite a bit of work I was reluctant to do after a hard day. I watched as the tanker closed in on me (AIS gives great detail about the ship's speed and course so the risk of collision is plain to gauge) and just as I decided I'd better set about it, a last glance at the laptop showed me the tanker had just altered course by 7 degrees, which showed he'd pass Scrumpy with a mile of clearance. The AIS transmission is in my opinion really well worth the extra cost over a receive-only arrangement.
And one other benefit is that family and friends can watch the boat's progress online, although MarineTraffic.com has a messed up database and is currently sending out erroneous positions for Scrumpy (it's in the yard in Totnes, with the AIS switched off!). Other tracking websites are available.
The VHF is a clever DSC one. It's good, but I very rarely use it. I don't like to hear all the calls to the coastguard asking for a radio check. Offshore, it's left on all the time, but I rarely call other ships.
I have a low tech wind indicator. I attached a bit of a plastic bag to my deck VHF antenna. Amazingly, it's been the same bit of bag for the whole of the Atlantic circuit, which is probably more reliable than a masthead indicator, and much easier to replace.
The Mervielle radar alarm works really well. I've had others that didn't. You had to fiddle with the sensitivity. Too high, and the alarm went off with every bump. Too low, and ships went sailing by with no response from the radar alarm. With this one, every ship but one was detected (a ship off the Canaries, that also had no AIS signal - spooky!). It has a little dome-shaped antenna I keep on a surface in the saloon. That's high enough to trigger the alarm when a ship is 2-3 miles away. You wouldn't want it going off more frequently by having the antenna higher.
So important, I have three. One still under warranty, used only from the Azores to the UK. Another, steers fine, but the display isn't working right. Both Autohelm 2000. And an older Autohelm. Less power efficient, more clunky, but it works fine.
GME MT403G GPS Epirb - one with GPS built-in to assist search and rescue. Unused.