The goal is to have your cake and eat it too, and that means being mindful of power consumption, and making sure every watt consumed is serving you well. This is front and center in our minds since we are now on day 55 without plugging into shore power. Since leaving La Paz at the end of February, we haven't plugged in once. We have spend a couple of weeks at the marina in Puerto Escondido, but the power is under construction and we have not had any for our whole stay.
It's along time without shore power, but everything is working just fine, and we honestly don't miss it. We recharge, do laundry, and make water while underway, or we run the generator if we are not underway. During the day most of our power needs are covered by our solar panels. This is all possible because we have paid close attention to appliance selection and electrical system design to minimize wasted power, while at the same time not giving up any of the conveniences that we want. With a little attention, we have our typical battery draw down to around 20A on average, when other boats of the same model are more typically in the 30-40A range.
One thing that has been really interesting over the past couple of years, and the subject of this article, is looking at where all our power goes. Some of it you might expect, but I'll bet there are some surprises as well.
Below is a table in rank order of the primary power consumers while we are at anchor going about our daily business. It is essentially the daily background load, but does not include any form of cooking, laundry, or any number of other things. So it's not an exhaustive study - just a snapshot of a bunch of things that are on pretty much all the time.
| Device | Watt-hrs per day | Notes |
| KVH V3ip | 3360 | |
| Sub Zero Fridge | 930 | |
| Ships Network | 864 | |
| Bosch Dishwasher | 770 | 1 full wash cycle |
| N2K network | 593 | |
| Water pump | 486 | |
| Panel meters | 432 | 12 meters total |
| Ship's Mac | 406 | |
| Nav Mac | 406 | |
| SeaFire | 300 | |
| LPG | 250 | On |
| AIS | 246 | |
| NavPixel Monitor | 234 | Full dim |
| Nav network | 234 | |
| FCV627 Fish finder | 180 | |
| Peplink Balance 20 | 134 | |
| Watermaker | 96 | Standby |
| Wifi Ext | 62 | |
| Netgear wifi stations | 62 | |
| LPG | 37 | Off |
I think if you ask most boaters what the biggest power consumer is on their boat, they would say it's refrigeration. And they would probably be right, unless they have a KVH sat device. Our KVH V3ip Sat phone and data system consumes 140W continuously which is three and a half times more daily power than the fridge which is the next high runner. Wow, what a pig. After discovering this, I turn it off at night to save power.
The fridge consumes a bunch of power, but considering it's a full size fridge and freezer, it's actually not bad at all and comparable to any other quality marine fridge.
The next big one is the boat's network switch. We have a 24 port gigabit ethernet switch, and because it's on all the time, it's power draw really adds up. I have been working on putting the commonly used things on a smaller, lower power switch, and only using the big switch when specifically needed. Turning it off would be almost like turning off the fridge from a power draw perspective.
Next is the dishwasher. We typically run it once a day, and the chart shows the power consumption for a full wash cycle. It's a lot, but we clearly get something in return.
Our N2K network adds up over 24hrs as well. It would be nice to get it down lower, but we use most of it for tank monitoring, weather, anchor watch, and alarming, so there isn't much we are willing to give up.
The water pump is a lot, and I think it's higher than it needs to be because of the way our Headhunter Mach 5 pump works. Most pumps cycle on when pressure drops below some level, run until pressure builds back up, then shut off. The Headhunter does the same, but it keeps running as long as there continues to be water flow. So, for example, it will run the whole time you are taking a shower. It has the benefit of maintaining constant high pressure the whole time rather than pressure that cycles up and down, but I'd estimate that it runs twice as long as a conventional pump doing the same thing.
A couple of other surprises are the power panel meters, the SeaFire engine shutdown system, and the LPG system if you leave the gas enabled. Down at the very bottom of the list you can see how much the LPG control power drops if you just turn off the gas when not in use, which you should do anyway....
Although they are not in the chart above, here are a few things you may want to watch out for on your own boat:
- A lot of entertainment electronics, especially older models, don't really turn off when you turn them off. They may go dark, but many keep drawing the same or nearly the same amount of power as when turned on. Cable and satellite TV boxes are particularly offensive in this regard, and can often be one of if not the largest power consumer in your house or boat.
- TVs have improved significantly in the past 5 years with respect to power consumption. First, to get an Energy Star rating, they have to actually stop consuming power when you turn them off, or at least drop down to a very low level. If you look at the EPA ratings, it will tell you what the standby power draw is. It should be less than a watt. And LED TVs are much lower power than older LCD TVs. So if you are looking an excuse to get a new TV, this might help.
- Some things may not be as bad as you imagine. Take a microwave oven. Yes, they draw a lot of power when on, but you typically only run them for a short time. If you run a 1000W microwave fro 5 minutes a day, that's only 83 watt-hrs per day, and would rank near the bottom of the list above.
- Refrigeration can be bad, or not so bad at all. A lot of people dump on sub-zero for being a power hog, but our particular model really isn't that bad, and is actually comparable with the most efficient alternatives of a similar size. On the other hand, I helped a friend who was having battery trouble on his boat, and his fridge was consuming eight times as much power as ours. In his case, I'm quite sure there was a problem with his fridge, but just looking at the EPA ratings you will quickly see that there can be significant variation in the performance of similar sized units, both for fridges and freezers.
- LED lighting makes a huge difference. Most 12V and 24V bulbs can be swapped for LEDs, and LED bulbs for 120VAC fixtures are readily available too. Our lighting power load is so low that I simply pay no attention to it at all anymore.
- As a corollary to LEDs, florescent lights do use a lot of power. Our engine room lights draw several hundred watts, and if left on are worse than the KVH. They are excellent candidates for replacement with LEDs.
If you are interested in digging into your own boat (or home) to see where the power goes, there are a few tools that will help.
First is a Kill-O-Watt meter which simply inserts between any plug-in appliance. It shows instantaneous power figures, and also totals up the power consumption over time which is particularly handy for things that cycle on and off like a fridge or water pump.
The next is a clamp-on ammeter. These are commonly available for AC power, but less common for DC power. If you want to measure the power for any DC device, you will need one that can measure DC current.
And for major appliances, I have found the EPA EnergyStar guides to be quite accurate. They have accurately predicted the power consumption for several refrigerators and freezers that we have had over the years, and at a minimum provide a good comparative guide.
