Why and how to go off-grid?

Why would I want to go off-grid if I’m building in my backyard and already have utilities?

Even with a fully prebuilt house from a factory, you still need months and tens of thousands of dollars to connect the electricity, water and sewer lines (in addition to associated permits). There’s no way to just order a house on Amazon Prime and move in within days.

…unless you go off-grid.

You might think it’s prohibitively expensive to go OG. However, if you design the rest of the house efficiently, it might be cheaper than a sceptic tank. We’ll show you how we do it with the Escape Pod at TinyBox, so that you can build OG on your own in an affordable way.

Energy

Solar Panels for everthing except heat

Solar panels costs around $0.50 - $1.00/W (including installation). Batteries are around $0.25-$0.50/Wh, about $0.50-$1.00/Wh when you account for charge controllers (MPPT) and inverters (to use 110V AC). A 100W panel generates between 200Wh-400Wh/day on average, depending on where you are.

We recommend you start with a list of all the electrical appliances you have and their associated power. This way you’ll ensure you always have enough power, while not overbuying solar panels and batteries. For the Escape Pod at TinyBox, we believe a fully functioning house will need a 2kw panel and 5kwh battery ($ 4,985).

Microwave draws a lot of power but only operates for 10-15min a day, so its power is high but energy is low.
AC is highly dependent on geography. Luckily if it’s really hot, there’s likely a good amount of solar power gathered. Roughly we need a peak of 20BTU/h or 7W per square foot. The Escape pod has about 75 square feet that’s not covered by cabinets, which requires a peak power of 1500BTU/h 500W

Energy and power required

Propane for everything heat

At $0.15/kWh*, propane is comparable to the price of electricity from the grid (especially if you account for monthly fixed costs from utility companies).

*This assumes $2k/kg, $1/L or $3.78/gallon, or $15/33lbs. 1kg of propane contains 50MJ of energy, which is equivalent to 14kWh.

Water

black water

Composting toilet is the most common offgrid options. It’s environmentally-friendly and doesn’t need water. The only drawback is the regular maintenance, which is not for everybody.

Dry flush toilet. This is what we recommend at TinyBox. Press a button and everything goes away, sealed into a smell-free bag. After years of experimenting with different toilets, this is what we prefer.

Recirculating toilet using a mini-bioreactor and micro-filters. At TinyBox we’re doing the R&D for a standard water-flush toilet where the only thing that comes out is clean water (which is reused to flush) and requires almost no maintenance!

Recirculating Shower

Normal showers use about 65L (17gallons) of water. They last 8min and water flows at 8L/min (2gallon/min).

An efficient shower can reduce consumption by 40%, with the best (Nebia) by 60%. That’s still a lot of water to store and transport, unless you resupply every few days. This is why we’re building a recirculating system, where the same water goes through a set of filter (to remove dirt, bacteria and viruses) so that water consumption as well as heating can be reduced by 90%-95%.

So, how is the water cleaned?

Shower drain (mesh strainer): Filters large stuff (e.g. hair)
Spin-down filter (100 microns): Filters sand, easy to remove empty the filtrates
Sediment filter (5micron): Filters dust, silt
Sediment filter (<1 micron): Filters bacteria & protozoa
Activated carbon (1 micron): Removes some odor and chemicals. This is what Brita filters are made of.
UV light (>40 mJ/cm2): Kill virus

Salts (including soap) are the only thing that can’t be fully filtered. To solve for that, we have solutions that limits the addition of soap in to the water and for disposing of it.

Limit soap: it’s simpler that you think! Use foaming soap/bodywash/shampoo. They do the job just as well but only contain about 10% of the soap.
Activated carbon filter. They still filter quite a bit of soap out.
Automated drain valve. At TinyBox, we’re currently doing the R&D of a valve that automatically opens (to drain water into a grey water tank) when it detects soap and salts in the water.

Washing stuff

To wash dishes, fruits & vegetables, and clothes, there are now small standalone machines that have their own water tank, only use 3-5L per load. They don’t require any plumbing so are not affected by building/zoning codes.

Water source

Rainwater

Water STorage

ICB Totes

At around $1.50/gallon, this is a cheap and space-efficient way to store water. More robust versions can be stored underground for visual purposes to protect against freezing.