What MHHS actually is
Until 2026, most UK electricity bills were calculated on profile-based settlement: your supplier estimated when you used electricity and was settled at average prices. From 2026, every meter reads in 30-minute intervals, and your supplier is settled at actual half-hour wholesale prices. This unlocks proper time-of-use tariffs.
What changes for your business bill
Same total kWh, but priced against the actual half-hour you consumed. Peak periods (16:00–19:00 weekdays in winter) carry higher prices; off-peak periods (overnight, weekends) carry lower prices. For most commercial buyers without battery: bill goes up 5–15% as peak hours dominate. With battery + load shifting: bill can drop 10–25%.
The arbitrage opportunity
Charge battery from cheap overnight wholesale (3–7p/kWh) or surplus solar (effectively free), discharge during expensive evening peak (25–40p/kWh). A 50 kWh battery cycled 250 times/year arbitraging a 20p spread = £2,500/year in arbitrage alone, on top of self-consumption.
Commercial tariffs to look for in 2026
Octopus Agile Business: half-hourly wholesale prices passed through to customer with a small premium. Octopus Go Business: cheap overnight (00:30–05:30) + standard daytime. EDF Time-of-Use SME: 3-band tariff. Drax E-Flex: peak-shaving with day-ahead notification. Pick based on your battery sizing and load profile.
Battery sizing for MHHS arbitrage
Rule of thumb: battery should be sized to your daily peak shift kWh — i.e., how much of your evening load you want to cover from stored midday solar or cheap overnight wholesale. For most SMEs that's 30–80 kWh. Larger sites (cold storage, data centres) need 200–500 kWh.
Why MHHS makes batteries pay back faster
Pre-MHHS, batteries paid back via Self-consumption + occasional export at SEG (5–15p/kWh). Post-MHHS, batteries pay back via: (a) Self-consumption shifted to peak hours (20–35p saved). (b) Arbitrage against cheap overnight wholesale. (c) Grid services (Dynamic Containment, DSR) — paying £80–£200/MWh for frequency response. Combined, payback can drop from 7+ years to 4–5 years.
A cold-storage example
Illustrative, not a named KMM customer. Cold storage runs 24/7 with compressor cycling, so its evening demand (16:00–19:00) is where time-of-use rates bite hardest. A battery that shifts midday solar into that window avoids peak-rate imports — value a simple annual-kWh payback model misses, and exactly what half-hourly data lets you price.
If you don't have a smart meter yet
MHHS only works if your meter reads HH. Most commercial meters already do (CT-clamp metering). If you're on a profile-class meter, request HH upgrade from your supplier — Ofgem-mandated, free, takes 2–4 weeks.
