Living on an anchored sailboat is living about as far off the grid as you can get. There are no public utilities at sea. In recent years, innovations in cellular and satellite telephony, computers, and the plethora of online services have changed things a bit, but not at a basic level. At a basic level, we are on our own as far as water and electricity are concerned. Fresh water is precious where we live, but with care and ingenuity, collecting rain meets our needs. As for electricity, we've tried an number of different ways to cope.
As with water, our first step is to minimize use. We use almost no energy to heat or cool our living space; we depend on shade awnings, breeze, and choosing a location with a benign climate for those things. We cook with bottled gas, and it's surprising how long a 20 pound tank of propane lasts. We normally use one tank for about four months. Our water for bathing is heated by the sun. Our lighting is almost all from highly efficient LEDs; we got rid of incandescent lights years ago. Even when LEDs were expensive, it didn't take long to recoup the investment.
So, what's our biggest consumer of electricity? Would you believe the refrigerator? Right on the heels of the refrigerator comes…the computer and all of those related gizmos. Our total electrical consumption is about 50 kilowatt-hours (kWh) per month. In 2010, the average annual electricity consumption for a U.S. residential utility customer was 958 kWh per month. The corresponding average monthly electric bill was $110.55.
We aboard Play Actor already look pretty green; we use about 5% as much electrical energy as an average U. S. household uses. But what does it cost us for our 50 kWh per month? All of our electrical energy is stored in a battery bank, and the bank holds enough electrical energy to last us for a day and a half, so in a typical month, we have to recharge those batteries about 20 times.
If we used the most basic approach and ran our auxilliary engine to charge our batteries, we would have to run the engine for 133 hours per month. That's $150 per month in diesel fuel, at $5 per gallon, not to mention the wear and tear on the engine, maintenance, etc, which will easily double that cost over the life of the engine, so we're looking at about $300 per month, and that only buys us 5% as much energy as the average residential user consumes. That average U.S. household would pay about $6 for the amount of electrical energy that we use.
There are a number of ways to make burning fossil fuel to recharge our batteries more efficient, including bigger alternators, highly efficient generators, etc. Those options require a sizable capital outlay, but none even comes close to getting our cost down to what the average U.S. residential customer would pay for our paltry 50 kWh.
We could turn off the refrigerator and unplug the computer, and some do. Or, we could invest in alternative sources of energy. Most long-term cruising boats choose this approach. Aboard Play Actor, we have a wind turbine, which works well enough in the tradewind belt where we spend most of our time, but it still only provides part of our requirement. We also have solar panels. For most of the years we've cruised, we've had a small photovoltaic array. The wind turbine and the solar panels met about 90% of our requirements, but still required us to run that diesel for a few hours a couple of times a month.
When we replaced the engine last year, our high-output alternator wouldn't fit the new engine, and our engine run time to charge the batteries doubled. We looked into a new high-output alternator that would fit, and realized that for less money, we could double the size of our solar panel array. That's what we did. We don't run the engine to charge the batteries, ever, now. We rarely run it to move the boat, except in close quarters where it's just not practical to sail, and Leslie wakes up happy because we have full batteries.
It's great to be green!