Charging EVs, in older, smaller houses with limited electricity

By Eugen Dunlap, Member, Sacramento Electric vehicle association

​We live in a small 1991 townhouse in Davis, California. My dream and goal has always been to transition from our current natural gas system and into using solar energy for our home as well as our vehicles.

But how is that actually achieved? While many newer homes might already have a 200amp electrical panel, making upgrades easier and cheaper, our townhouse connects to a single 100amp/240V electricity line.

What about upgrading the incoming line to 200amp?  Sounds easy, doesn’t it? Not so fast; our electrical line is buried underground and is relatively long, two huge disadvantages when it comes to upgrading. I would need a bigger and thicker cable coming up into the house, and cost estimates to make that happen are in the $30,000 range. What’s more, the street transformer is already maxed out, so an increase in power is likely impossible even if we could upgrade.  

Another alternative would be to practice diligence in performing load calculations so as not to overload the line. But, given the loads I am imagining, this is not the best solution either. 

So, what are the facts?

My 240V house load consists of 40amp EV, 40amp heat-pump, 30amp hybrid water heater, 40amp electric stove, 30amp dryer and lights/outlets, and 40amp for the solar hookup and possible battery backup. (Note: All amps listed are outlet/fuse ratings, so not close to actual load.) 

Clearly, 100amp doesn’t go very far. To see how your own home would fare with your existing electrical panel, use this calculator.  

Another possibility would be to replace all my 240V loads with the lowest possible amp-draw equipment and appliances in order to save energy. So, for example, one might replace a standard 30amp dryer with a 20amp dryer. The problem here is that choices are limited and savings are limited, too.

Smart control is key

At the January 2022 InterSolar event in Long Beach, California, I came across an intriguing solution: use of a smart electrical panel. Upon consideration, it appeared that this might be my only real choice, as it would provide active management to assure staying within the 100amp limit. This can be accomplished because the appliances used in my home are almost never utilized at the same time. 

This solution enables one to charge an EV and switch over completely to electricity/renewable energy without ever overloading the system. Realistically, the cost of such a panel is not cheap (approximately $3500) and an electrician would likely charge an additional $3500 to install it. However, when compared to the quotes I received to upgrade the line, it is a far less expensive option.

Span, a firm with a booth at the InterSolar event, shared valuable information on its smart electrical panel product. Lumin, using a separate electrical box, also presented its product, but  was not quite as elegant as the Span offering. Whatever variation on this product is ultimately successful, this does seem to be what the future holds.