Multi-Let Building Solar Metering: A Landlord's Guide

On a single-occupier building the metering question answers itself: one meter, one bill, one beneficiary. On a multi-let building it is the whole project. The array can be perfectly sized and well installed and still deliver nothing to you if the meters do not let you show who consumed what.

This guide covers the metering architecture an owner should understand before commissioning solar on a let building. The commercial argument for starting with the landlord’s own supply is in our common-parts solar guide; this article is about the meters that make it measurable.

Three kinds of electricity in one building

A multi-let building usually has three separate flows of electricity, and each has a different owner.

• The landlord supply. Lifts, communal lighting, plant, car park and security. The landlord holds the contract, pays the bill and normally recovers the running cost through the service charge.
• Tenant supplies. Each tenant has its own meter point and its own supply contract. The landlord has no claim on that consumption unless a contract creates one.
• The generation. The solar array, which has to be connected behind one of those meters.

Where you connect the array decides who benefits. Connect it behind the landlord’s meter and it offsets power the landlord already pays for, with no tenant involved. Connect it so it feeds tenant loads and you have created a supply relationship that needs a contract, which is the split incentive in practical form.

Start with the landlord meter

The simplest and cleanest arrangement is a dedicated meter point for the landlord supply, with the array connected behind it so that generation offsets that supply and nothing else. Because you are not selling power to anyone, you do not need a PPA or a sleeving arrangement for this part, and the measurement is straightforward: import before solar against import after.

Check two things early. First, whether the landlord supply is genuinely separate today; in older buildings common-parts loads are sometimes wired through a tenant’s meter, and untangling that is a cost to price in. Second, whether the landlord meter is half-hourly, because half-hourly data is what lets you model the load against the generation profile.

When tenants are involved: sub-metering

If any of the solar output is to be apportioned to tenants, you need measurement that holds up if someone challenges it. That is the case for MID-approved sub-metering, meaning meters approved under the Measuring Instruments Directive. These give you billable accuracy, the evidential standard for reconciling charges, and a foundation for any later PPA layer.

Sub-meters also let you do the thing most owners want: show a tenant what it saved. The savings figure that underpins a capped green-lease contribution is measured self-consumption against a grid reference price, and without sub-metering that figure is an estimate. The contribution mechanics are in our green lease and solar guide.

The half-hourly data you need

Ask for half-hourly consumption data before you size anything. It shows when the building uses power, which determines how much of the generation is consumed on site. Self-consumption is the biggest single driver of return on a commercial array, and a daytime weekday load profile such as lifts, ventilation, car park use and EV charging matches solar output well. Data also lets you check, after commissioning, that the savings you report to tenants are measured rather than assumed.

A short pre-commissioning checklist

1. Confirm the landlord supply sits on its own meter point.
2. Obtain twelve months of half-hourly data for it.
3. Decide whether any output will be allocated to tenants; if so, specify MID-approved sub-meters.
4. Check each lease for access rights and for any clause that affects metering or data sharing.
5. Agree who owns the meter data and who can read it.

Frequently asked questions

Do I need sub-metering for common-parts solar?

Not for the energy flow itself, if the array sits behind a dedicated landlord meter. You need it if you want to allocate output to tenants or prove savings to them.

What does MID-approved mean?

The meter is approved under the Measuring Instruments Directive, which gives it the accuracy standard needed for billing and dispute resolution.

Can I recover the metering cost through the service charge?

That depends on the lease wording and on whether the cost is capital or running. Capital cost of new plant is not generally recoverable under the RICS Service Charges standard, so take advice on the specific item.

Where do I get help scoping this for a building?

Send an enquiry with the building, the tenancy structure and a postcode, and we reply by email.