We have been SO busy trying to meet our departure date of April 20! I can't believe how quickly we will be on the road on our way to New Orleans! We've gotten a lot done and are nearly move-in ready, but let's take a step back and focus on the details of our electrical system.
Like the rest of the house design, our electrical system has both an on-grid and an off-grid option. We purchased a solar panel, battery, and inverter to allow us to have lights, even if we have no power connection. The diagrams below show the two scenarios for receiving power and a list of the items we purchased for this system.
1) Plugged into a physical 120V power connection at a house or RV campsite.
At an RV campsite, this could be 30A or 50A feed, but at a friend's house, it's most likely from a 15A outlet. Our inverter has a 30A breaker at the output which feeds our breaker panel, so our panel has no main breaker (it's main lug only). In general, we don't expect we'll ever trip even a friend's 15A breaker in their house. Our highest power draws are our counter top convection toaster oven (max 1800W or 15A) and my hair dryer. The LED lights and small refrigerator help keep our other power needs low.
List of items purchased:
- Solar Panel
- Solar Charge Controller
- Lead Acid AGM Battery
- Power Inlet, Cable, and 15A adapter
- 2000W Inverter
- 100A Main Lug Only Breaker Panel (purchased from our local hardware store)
2) Running off our battery and collecting solar power.
Our solar panel can collect 100W continuously, which means it can provide ~8.3A to our battery to charge it. We monitor what we're getting from our panel via our solar charge controller and have only seen 5A max, when the sun in shining bright. Solar panels are very directional, that's why being able to move it freely to track the sun is ideal. Our panel will be stored in our house while we're moving and set up in the best possible location when we're parked. Mounting a panel on the roof or exterior wall would mean that the house would need to be positioned with that particular side facing the sun, which might not always be possible. The great thing about solar panels is that you can always add more. We will assess how our system is performing, once we get a chance to try it out for real!
We went with a lead acid sealed AGM battery that's 12V and has 100 Amp-hour capacity, meaning it could provide us with 1A for 100 hours, 2A for 50 hours, etc. When we're solely on battery power, we will not be using our convection oven or hair dryer. Our only loads will be our lights, fridge, water pump, water heater (which is propane but draws a little power for the screen and starter), and any other miscellaneous items plugged into outlets like a phone charger. We estimatee that the average continuous power usage when off-grid and trying to conserve energy is about 30W (with two lights, the fridge, and the water heater all on). That means that our battery could keep us running for 40 hours. However, when the fridge or water pump kicks on occasionally, it will drain the battery more quickly. Anything the solar panel can provide helps to increase our estimated battery life.
The inverter we purchased is rated for 2000W. This should be able to handle any larger appliances we run in our house. The inverter converts the 12VDC battery to 120VAC to feed our breaker panel when on battery power. When we're plugged in, it simply passes the 120VAC straight through to our panel, while also taking advantage of the power feed to charge our battery.
We purchased an 100A 8-circuit main lug only breaker box, which is plenty for a tiny house. We have 15 outlets and lights, because, well, can you really have too many? The abundance of lights (on many different switches) allows us to be very selective with our lighting. Some are bright and directional for task lighting, some are more ambient. All the outlets allow us to charge our phone or laptop wherever we want!
We really enjoyed designing and installing the electrical system. Both of us studied electrical engineering in school, so it was fun to feel like we knew what we were doing for once (ha!). It's also a huge milestone to turn on that first light or plug in the solar panel and see it charge our battery.