The Seattle Times has an fascinating article that talks about two big reasons new middle housing projects may need undergrounded power supplies in Seattle – electric heat pumps and EV charging capability (at a time when new projects might need power going to four or six homes per lot).
Adding the tubing for an underground electrical connection and making street improvements at the time of construction was said to add 6% to the cost of one recent project. Cost depends very much on whether the existing power lines are on the opposite side* of the street, and will also vary depending on whether the lengthy process of getting Seattle City Light (SCL) approvals takes months or years.
Under SB 5290, Bellevue and Seattle have already been working to speed up the permit review process. The developer community gets frequent updates about our average permit approval times at the Bellevue Development Committee meetings. Depending on interest rates, the approval timelines can be very important for helping a project succeed financially. It does not appear that this covers approvals from non-city entities like PSE, however, and I do not know whether they are as slow as SCL.
To be fair, it is hard to imagine a middle housing development like this not needing a larger water supply line, which should also require excavation, and having an underground pipe for the electrical connection also has the advantage of facilitating future communications upgrades, such as adding fiber. It’s not clear what street improvements were made as part of that 6% of cost, and if they are valuable on their own. If you have experience with this, I would be interested in hearing your take.
One difference in Bellevue is that EV charging/EV ready wires in the walls were not required for Middle Housing when Bellevue’s City Council voted on the new rules in June 2025. I had assumed that this would mean individual homeowners would be on the hook for installing those wires (and possibly upgrading the electrical panel) later, and that was disappointing from a sustainability and customer protection standpoint. I didn’t realize that constraints on electrical supply to the new homes might make it functionally impossible to add on later.
On the other hand, in Bellevue this could be a greater concern because we’re allowing more homes per lot than Seattle; builders here are able to put six units of middle housing and 2 ADUs on each lot** (though in some cases they’d need to pay in $150k each for two of those units to an affordable housing fund). Of course, it’s not a requirement that there be eight homes on each lot, and four homes per lot is more likely to give families the Bellevue suburb lifestyle with room for kids to play.
Some of the proposals for addressing this problem: stronger poles may be able to hold up the heavier wires and larger transformers, but they are said to be unsightly (will be tested in Seattle this year, still expensive), smart panels may be able to limit EV charging when power consumption is being maxed out (a fourplex might have throttling only 1% of the time, but this is not yet approved in code), and some housing advocates say that existing residents should subsidize the new middle housing being built in their neighborhoods through a broad-based tax (though this is likely to impact residents whose homes are worth less than the new housing being added).
*Developers are also using AI to identify investment opportunities, probably factoring location details like this, and this is a time of particularly asymmetric information – home sellers won’t know whether their properties are potentially cheap to build on if they’re not aware of things like this and the history of recent utility upgrades in their areas.
**Seattle also has reductions in density if a portion of the lot is unbuildable wetland or steep slope, as is common in various jurisdictions, while Bellevue removed that provision with our recent Critical Areas Ordinance update. Bellevue is currently considering changes in the minimum lot size, which will enable twice as many units on some of the larger lots, since they could then have 8 or 24 units each, for a total of 16 or 48.



