Transformer Upgrade Required?

[jdr93]

The same way my power company puts 7 houses on a 50 kVA transformer. The models they use to allocate power and plan their transmission and distribution network don’t include electric vehicles. They work on the assumption that houses on a transformer won’t have simultaneous high loads. That will obviously need to change as EVs become more prevalent.

that is a really good point

 

[gnuarm]

The same way my power company puts 7 houses on a 50 kVA transformer. The models they use to allocate power and plan their transmission and distribution network don’t include electric vehicles. They work on the assumption that houses on a transformer won’t have simultaneous high loads. That will obviously need to change as EVs become more prevalent.

I have been concerned that home EV charging would end up with the local utilities upgrading local feeds to accommodate the increased load to the neighborhoods. Many have posted that this just won't be a problem. Now that I've been told a neighbor needed an increase in the feed to his house to install a pair of chargers, I'm wondering if this may be a realistic concern.

My actual concern is that they will want to adjust rates to pay for increases.

My local utility will be giving a $7 a month credit on your bill if you simply agree to not charge during peak times. That says a lot about what they pay for peak generation and transmission, but not for the impact on the local distribution. Overall, the grid is most impacted at standard peak times, ~6-9am and ~3-7pm with differences between summer and winter. The local distribution for a residential community with a lot of heat pumps may be more impacted on cold, winter nights when the resistance heating is cranking. I think my furnace uses 10 kW. Add another 15 kW for charging two cars at many houses and I'm thinking they will be needing to upgrade some equipment. We've had a cold spell the last month or 6 weeks. I see my hourly readings and it's over 11 kW most of the night sometimes.

 

[Cores]

The same way my power company puts 7 houses on a 50 kVA transformer. The models they use to allocate power and plan their transmission and distribution network don’t include electric vehicles. They work on the assumption that houses on a transformer won’t have simultaneous high loads. That will obviously need to change as EVs become more prevalent.

The utilities currently have no plan to increase capacity of the the pole/pad MVDT (Medium Voltage Distribution Transformer). They are still installing 10kVA to 25kVA units hoping that the EV problem will just go away.
There are other issues besides the transformer overload issue. Installing a higher-capacity MVDT increases distribution losses in the form of no-load losses. We will all be best benefitted if the utilities install low no-load loss transformers to keep our bills down. Utilities are not paid more money to increase efficiency. Whatever energy is wasted at the transformer is added to our bills - frequently in an electric distribution fee.