How-to

How to Calculate New Rent After the CPB Utility Rule

Published June 1, 2026 · 6 min read

CPB Notice 2018 wiped out the utility-margin profit for 5+ unit dorms. This is a simple 3-step formula to set the new rent, three worked cases (small/mid/big), and a free calculator that takes 30 seconds.

TL;DR

Formula: (old rate − actual rate) × usage per room = lost margin/room/month = the amount to raise rent by
Example: 2.6 THB/unit gap × 80 units = 208 THB/room — raise rent 208 THB to break even
Don't forget the %. 208 THB is 7% of 3,000 rent — tenants feel that very differently from 4% of 5,000
Use our free calculator to plug in your dorm and see instantly (link at the end)

Try the calculator — your dorm's numbers

Free, no signup, 30 seconds, instant answer. Supports both metered and flat-fee billing.

The 3-step formula — new rent in 3 lines of math

For dorms that bill by meter (THB/unit), do this:

1
Find the per-unit price gap
Old rate you charged tenants minus the actual provider rate. Do this separately for electricity and water.
Gap = old rate − actual rate
2
Multiply by average usage / room / month
Look back 3–6 months and average. Typical: electricity 60–100 units/room, water 3–7 m³/room (AC use shifts this a lot).
Lost/room = (elec gap × elec units) + (water gap × water units)
3
Round up slightly + check it as a % of rent
That number is what you need to raise rent by to break even. Round to a clean number, then compute it as a % of current rent to gut-check whether tenants can absorb it.
% = (increase ÷ current rent) × 100

💡 Tip: If you bill flat (e.g. 500 THB/month flat for electric), just use (flat charged) − (actual cost per room from your provider bill ÷ rooms in use) instead.

Three worked cases — small, mid, big dorm

Same formula, different scale and behavior:

Small (10 rooms)

10 rooms, 90% occupancy (= 9 rooms), 2,500 rent. Usage: elec 60 units, water 4 m³. Old: elec 7 / water 18. Actual: elec 4.4 / water 18.

Elec gap = (7 − 4.4) × 60 = 156 THB/room
Water gap = (18 − 18) × 4 = 0 THB/room
Total gap = 156 THB/room/month
Lost revenue = 156 × 9 = 1,404 THB/month → 16,848 THB/year

Raise rent 156 THB/room = 6.2% of 2,500

Mid (30 rooms)

30 rooms, 80% occupancy (= 24 rooms), 3,000 rent. Usage: elec 80 / water 5. Old: elec 7 / water 20.

Elec gap = (7 − 4.4) × 80 = 208 THB/room
Water gap = (20 − 18) × 5 = 10 THB/room
Total gap = 218 THB/room/month
Lost revenue = 218 × 24 = 5,232 THB/month → 62,784 THB/year

Raise rent 218 THB/room = 7.3% of 3,000

Big (60 rooms, A/C)

60 rooms, 85% occupancy (= 51 rooms), 5,500 rent. Usage: elec 150 / water 6. Old: elec 8 / water 25.

Elec gap = (8 − 4.4) × 150 = 540 THB/room
Water gap = (25 − 18) × 6 = 42 THB/room
Total gap = 582 THB/room/month
Lost revenue = 582 × 51 = 29,682 THB/month → 356,184 THB/year

Raise rent 582 THB/room = 10.6% — too much in one go. Blend with service fees / cost cuts.

5 pitfalls before you announce it

Math right, communication wrong — you lose tenants and net less than the margin you tried to recover. Watch these:

#1Don't use a one-off extreme month for usage

Hottest/coldest months aren't typical. Use a 6-month or full-year average for honest numbers.

#2Remember occupancy isn't 100%

Dividing by total rooms inflates the gap. Lost revenue only happens on occupied rooms — use the average.

#3Don't raise existing tenants mid-contract

Not allowed. Wait for renewal + give 30–60 days notice. New tenants can start at the new rate immediately.

#4Don't set a high service fee without delivering service

A '฿500/month common-area fee' with no actual service = the same kind of rule-dodging as utility markup. Tenants can challenge it.

#5Check the latest Ft cycle

MEA/PEA Ft adjusts every 4 months. This month's actual rate may not be last year's — use a recent bill.

FAQ

Will tenants accept the new rent?

Depends on communication. With facts (new law + real numbers), most accept it — long-term tenants rarely move for ฿200–300 because moving + new deposit costs more.

I don't want to raise rent but also don't want to lose money. What now?

Try the 'cut real costs' path — LED across the building (30–50% electric reduction), fix leaks, rooftop solar. One-time investment, 2–3 year payback, beats bleeding monthly forever.

Tenants use very different amounts of electricity — can I use an average?

For estimating the total gap, yes. But raising rent uniformly feels unfair to light users — best fix is to install sub-meters per room and bill actual usage, which makes the question disappear.

Does the calculator support flat-fee dorms (no sub-meters)?

Yes — there's a 'flat fee' mode where you enter what you used to charge per room vs. actual cost (provider bill ÷ rooms in use). It outputs the same rent-increase number.

Can I raise gradually — half this year, half next?

Yes, common for owners who don't want to risk tenant turnover. Our calculator shows 'if you raise only half, you're still short THB X/month' to help you plan.

Try the calculator — your dorm's numbers

Free, no signup, 30 seconds, instant answer. Supports both metered and flat-fee billing.

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