What a mini split costs to run comes down to three numbers: how much heat the room gains or loses, how efficiently the unit moves it, and what Pepco charges you. Roomwise DC Mini Splits sizes each head from a heat-load calculation, which also gives you the first number. This guide shows how to put the three together.
What does electricity cost in DC?
Pepco’s current residential tariff for the District has a fixed monthly charge, then per-kWh charges for distribution, generation and transmission. Two details matter for a heat pump: the first 400 kWh is cheaper to deliver, and winter delivery above that costs less than summer.
| Pepco DC residential charge | Rate |
|---|---|
| Customer charge | $18.09 a month |
| Distribution, first 400 kWh | $0.01982 per kWh |
| Distribution above 400 kWh, summer (June to October bills) | $0.05659 per kWh |
| Distribution above 400 kWh, winter (November to May bills) | $0.03952 per kWh |
| Standard Offer generation, November to May | $0.14795 per kWh |
| Standard Offer generation, July to October | $0.14238 per kWh |
| Standard Offer administrative charge | $0.00440 per kWh |
| Transmission | $0.01924 per kWh |
Add the winter charges above 400 kWh and you get about $0.211 per kWh, before surcharges, riders and the delivery tax. That’s the rate a heat pump’s extra winter use is charged at. If you buy from a retail supplier, swap in your own generation rate from the bill.
How do I estimate what a mini split will use?
Divide the heat moved by the unit’s efficiency to get the power it draws. Then multiply by hours and your rate.
In cooling mode
EER2 tells you how many BTUs of cooling a unit delivers per watt at a hot test condition. A head delivering 9,000 BTU an hour with an EER2 of 12 draws about 750 watts (9,000 ÷ 12). Over eight hours that’s 6 kWh. At part load an inverter does better than its EER2; SEER2 averages that over a season.
In heating mode
COP tells you how many units of heat come out for each unit of electricity in. One kWh holds 3,412 BTU, so a head delivering 9,000 BTU an hour at a COP of 3 draws about 0.9 kW. The same heat from electric baseboard takes about 2.6 kW.
Putting it together
- Find the room’s load from the load calculation (the sizing guide explains it), or the head’s output at the conditions you care about.
- Divide by the efficiency at those conditions to get kW.
- Multiply by the hours it runs to get kWh.
- Multiply by the rate on your bill for the season.
What do SEER2, EER2 and HSPF2 mean?
They’re the federal efficiency ratings, measured under the current test procedure that added the “2”. Higher is better on all three.
| Rating | What it measures | What it tells you |
|---|---|---|
| SEER2 | Seasonal cooling efficiency | Summer running cost over a typical season |
| EER2 | Cooling efficiency at a hot test condition | How it does on the hottest afternoons |
| HSPF2 | Seasonal heating efficiency | Winter running cost over a typical season |
| COP | Heat out per unit of electricity, at one temperature | Efficiency on a given day; it drops as it gets colder |
DCSEU’s rebate tiers use the same ratings, from SEER2 15.2 and HSPF2 7.8 at Tier 1 to SEER2 16 and HSPF2 9 at Tier 2. The rebates guide lists both.
Is a mini split cheaper to run than baseboard heat?
Yes, nearly always. Electric baseboard turns each kWh into exactly one kWh of heat. A heat pump moves more heat than it uses, so it beats baseboard on every day it can carry the load.
How far ahead depends on the outdoor temperature. On a 45°F day the heat pump’s COP is high; on a 15°F night it falls, but stays above baseboard on a properly sized system. The winter guide explains why capacity and efficiency fall in the cold.
Is it cheaper to run than gas heat?
It depends on gas and electric prices, which move. On recent DC prices, a heat pump needs a seasonal COP of roughly 3.1 to match an 80% efficient boiler on cost, and about 3.7 to match a 95% gas furnace.
Those break-even points are a rough guide, not a promise. They leave out surcharges and fixed charges, and the gas customer charge stays unless the gas is shut off.
- Comfort and control are often the stronger reasons to switch: a head per room, and cooling in summer.
- Savings depend on the house, the equipment and the prices that year.
- The DCSEU rebate is larger when gas heat is replaced.
Is it cheaper than window units?
Usually, for the same cooling. An inverter mini split slows down as the room cools instead of cycling a fixed-speed compressor on and off, and its rated efficiency is typically higher.
It also stops the air leaks around a window unit’s frame, which cost money all summer. The mini split vs window AC guide compares the two side by side, and the central air comparison covers ducted systems.
What makes a mini split’s bill go up?
Settings and setup, more often than the equipment. These raise the bill without improving comfort:
- An oversized head that cycles instead of running steadily at low speed; see how many zones
- Deep setbacks that force the unit to recover at full speed
- Dirty filters that cut airflow and efficiency
- Doors open to unconditioned rooms, so the head conditions space it wasn’t sized for
- A blocked outdoor unit under snow or leaves
- A slow refrigerant leak, which shows up as longer run times and weaker output; that’s a repair
What does it cost to keep it running well?
A yearly professional cleaning keeps efficiency up and catches drain and refrigerant problems early. Roomwise’s typical range for a mini-split service visit is $150 to $400 for a one-head system, covering filters, coils, drain, electrical and refrigerant checks.
Each additional indoor head on the same visit typically adds $50 to $125. See maintenance for what the visit covers, and the installation cost guide for the upfront side of the budget.