Clark Public Utilities customer generation interconnection: tiers, fees and insurance

Q: How does Clark Public Utilities customer generation interconnection measure system size?

The published limits do not say whether they are measured in alternating or direct current.

How the size is measured: not published

The published limits here are stated in kilowatts without saying whether that is the inverter rating in alternating current or the array rating in direct current. On a system near a threshold that decides which band it lands in, so the checker asks the question rather than choosing an answer.

Size bands and what each one obliges

Tier 1, single phase 25 kW or less Size 0 to 25 kW	The application fee is $100. No additional insurance is necessary for a net metered facility at or below 100 kW that qualifies under RCW 80.60, which Clark states affirmatively. Clark is one of the few utilities in this region with a real inverter based external disconnect waiver below 25 kW, though it reserves the right to disconnect service entirely instead. $100 application fee UL 1741 listing certified to UL 1741SB and IEEE 1547-2018, which is mandatory rather than optional Electrical permit from Washington Labor and Industries or the City of Vancouver, not from the utility
Tier 2, 26 kW to 100 kW Size 25.001 to 100 kW	The application fee is $500. The aggregate on the transformer secondary must not exceed the lesser of the service wire capability or the transformer nameplate, fault contribution must stay under 10 percent of the circuit maximum fault current, and short circuit current above 87.5 percent of rating disqualifies. $500 application fee Fault current and short circuit screens
Above 100 kW, net billing rather than net metering Size 100.001 to 20000 kW	A system above 100 kW may still be approved under a net metering agreement, but only the portion at or below 100 kW is eligible for net metering. The remainder is separately metered, delivered directly to the utility, and purchased at avoided cost under federal law. Non net metered tiers run $500 above 25 kW to under 500 kW, $1,000 from 500 kW to under 20 MW and $2,000 at 20 MW and above, all non refundable. Non refundable application fee by tier Separate metering of the portion above 100 kW Insurance may be required above 100 kW at the utility’s discretion

Tier 1, single phase 25 kW or less Size 0 to 25 kW

The application fee is $100. No additional insurance is necessary for a net metered facility at or below 100 kW that qualifies under RCW 80.60, which Clark states affirmatively. Clark is one of the few utilities in this region with a real inverter based external disconnect waiver below 25 kW, though it reserves the right to disconnect service entirely instead.

$100 application fee
UL 1741 listing certified to UL 1741SB and IEEE 1547-2018, which is mandatory rather than optional
Electrical permit from Washington Labor and Industries or the City of Vancouver, not from the utility

Tier 2, 26 kW to 100 kW Size 25.001 to 100 kW

The application fee is $500. The aggregate on the transformer secondary must not exceed the lesser of the service wire capability or the transformer nameplate, fault contribution must stay under 10 percent of the circuit maximum fault current, and short circuit current above 87.5 percent of rating disqualifies.

$500 application fee
Fault current and short circuit screens

Above 100 kW, net billing rather than net metering Size 100.001 to 20000 kW

A system above 100 kW may still be approved under a net metering agreement, but only the portion at or below 100 kW is eligible for net metering. The remainder is separately metered, delivered directly to the utility, and purchased at avoided cost under federal law. Non net metered tiers run $500 above 25 kW to under 500 kW, $1,000 from 500 kW to under 20 MW and $2,000 at 20 MW and above, all non refundable.

Non refundable application fee by tier
Separate metering of the portion above 100 kW
Insurance may be required above 100 kW at the utility’s discretion

The screens that decide it

Fifteen percent of line section or circuit annual peak load 15 percent of line section peak load, a figure only the utility holds.
Aggregate nameplate on any line section may not exceed 15 percent of the line section annual peak load as most recently measured or calculated, or 15 percent of the circuit annual peak load. Note the denominator is annual peak load rather than minimum daytime load, and the same screen appears in both the net metered and non net metered rules.
Transformer secondary and 240 volt imbalance limits
Aggregate capacity on the transformer secondary may not exceed the transformer nameplate, or for Tier 2 the lesser of the service wire capability and the transformer nameplate, and the system may not create an imbalance of more than 5 kVA between the two sides of a 240 volt service. On a spot network the ceiling is the smaller of 5 percent of maximum network load or 50 kW.

Ask the utility this, before you sell it

Is the tier boundary measured on the inverter AC rating or the array DC rating? The scope and the web page say 100 kW AC while the definitions section of the same document says the DC rating of the panels, and the answer decides both the $100 or $500 fee and the review path.
Will the external disconnect be waived for this inverter based system under 25 kW? Clark permits proceeding without one under conditions but reserves the right to disconnect service entirely instead, so confirm per job.
What is the annual peak load on this line section and circuit?

Worth knowing before you quote

Published review clocks are in business days: a best effort to approve, approve with conditions or deny within 20 business days for both net metered tiers, 20 for Tier 1 and 30 for Tiers 2 and 3 under the non net metered rules, acknowledgment of receipt within 20, and 60 business days for the applicant to complete a deficient application. Approval expires if the facility is not interconnected and operating within one year, unless the utility grants a written extension at its sole discretion. No aggregate program cap and no percentage of consumption cap are published. Standby or backup generators not intended to operate in parallel are outside these rules and are negotiated case by case. Any future modification or expansion needs prior utility review and approval, so adding a battery to an existing array is a new review. The application goes to the utility by email or post office box and the customer signs it, with the installer typically preparing it.

Source

Clark Public Utilities Attachment A, Customer Generation Interconnection Standards for Net Metered Facilities 100 kW or Less, revised 5 April 2022, with the Generator Interconnection Requirements revised 9 August 2024

Read and recorded 2026-09-12. Municipal or public utility, outside its state's interconnection rule. Its own published documents govern. A Washington public utility district. Washington RCW 80.60 binds it for net metering. The superseded 2014 standards with 0 to 25 kW and 26 to 300 kW tiers are still online and must not be used.

All Washington interconnection rules

Size bands and what each one obliges

The screens that decide it

Ask the utility this, before you sell it

Worth knowing before you quote

What to do with this