With the announcement of the Tesla Powerwall, we have been asked if the Tesla Powerwall is something that will help missionaries. The short answer is “No”, at least for now. Read on for a more technical explanation, or just know that the NTM Tech Center is always on the lookout for new technologies and products that may assist missionaries.
The Tesla Powerwall is a battery energy storage device, it contains Lithium batteries, and is designed to charge (purchase electricity) when the price of electricityis low, and discharge (sell electricity) when the price of electricity is high. Most residential households in the United States and the rest of the world do not pay different prices for electricity throughout the day. However, many commercial and industrial users do, and as the “smart grid” is expanded, more residential users may pay differently throughout the day. This helps reduce peak loading, absorbs extra PV solar electricity, and stabilizes the electric grid. If there is a significant difference in the high price and low price of electricity, a profit can be made. However, in the US and most developed countries the price of electricity is relatively low to begin with, from $0.06 to $0.40 per kW/h. Assuming that you can save $0.10 cents per kW/h of electricity (buy low, sell high) the 7 kW/h Tesla Powerwall can save you $0.70 per day, $255.50 per year, and $2,555.00 over its 10 year warrantied life span. The 7 kWh Tesla Powerwall costs $3,000 and does not come with an inverter ($1,000 – $4000). A qualified electrician will need to install the Tesla Powerwall ($500) and additional breakers, wires, electrical box and even a new electrical meter may be needed ($100 – $4,000). This totals $5,100 – $12,000. So like most PV solar installations in the US, unless you are getting a utility rebate, tax credit, or someone else is paying the costs, the Tesla Powerwall is not cost effective for a residential household. For a power utility or large commercial and industrial users, it can be more cost effective and beneficial.
Some of the main disadvantages with the Tesla Powerwall for use by missionaries are:
- High battery voltage, 350 – 450 volt DC.
- Inability to directly power 12 volt DC appliances, requiring the constant use of an inverter or DC-DC converter.
- Incompatibility with all existing Charge Controllers, Inverters and DC loads missionaries are currently using.
- Lithium batteries require different charge cycles compared to lead acid batteries.
- 220 lb shipping weight will make it difficult to haul into some remote locations.
- Only one size capacity, the 7 kW/h, is available. (The 10 kW/h model is not designed for daily cycling.)
What does excite the NTM Tech Center about the Tesla Powerwall is the lower cost per kW/h for battery storage and longer life. Currently missionaries are paying about $570 for 1 kW/h of battery energy storage using AGM lead acid batteries. The Tesla Powerwall costs $430 per kW/h. In addition, typical off-grid AGM lead acid batteries only last about 5 years, compared to the 10 year warrantied life span of the Tesla Powerwall. However, a typical missionary household only needs about 2 – 4 kW/h of battery energy storage, so even the small 7 kW/h Tesla Powerwall is 2-3 times too large for most missionaries.
In order to build Tesla electric cars and the Powerwall battery system, Tesla is building a giant battery factory to produce massive amounts of Lithium batteries, this will help drop the price of Lithium batteries worldwide. We are expecting in the next few years other manufactures will begin selling Lithium batteries designed specifically for off grid PV solar installations at very reasonable costs. In addition more manufactures will design equipment such as Charge Controllers and Inverters to properly charge and utilize Lithium batteries in off grid installations. When such equipment becomes available, we will purchase it and begin testing it for use by missionaries.